How much Horse Power do you think this needs?????

[Ravencry]

30400
Hey guys, This is my question. I need a boat that can hold around 5500LB and plane off. This is the design that I was thinking of. I would probably make it out of wood, seeing that I live in the Jungles of Peru and wood is cheap. My problem is that I would not want to buy a outboard and then not have enough Horse Power. That would be a waste of money. The weight would consist of: Motor, Gas, 12 people, luggage, roof, and the weight of the boat, which I approximate around 1700LB, this all equals out to around 5500LB. I don't need to fly, but I would want it to go over 20 MPH. I want enough Horse Power but not to much. I don't need to go over 35 MPH. Thanks for your help and your pearls of wisdom. Ravencry

[Willallison]

Lets leave the question of power and weight for a moment and look at your design. The 1st thing that strikes me is that you've shown a boat that has round chines throughout, which is less than ideal for the application that you're describing.
Also the sections are all quite round up forward, so this boat would pound terribly in any chop.
I would suggest that you'd be far better off buying a set of stock plans. There are any number available that would suit your needs.

[PAR]

Nothing personal Ravencry, but your efforts with FreeShip haven't produced a viable craft for your application. It has so many issues wrong with it, that I will not bother going into them. Considering your designing skill level, you should be strongly urged to take Will's advise and find a set of plans.

[Ravencry]

I was going for a design that the Long tail boats from Asia have. This boat would be on river, so chop is not so much a problem. I have read that a flatter bottom would make planing easier, and since I am trying to go with as little HP as possible I wanted something that would plane more readily seeing that I it would be carrying so much weight. But if the design is faulty, I am man enough to take the criticism and go another route. Ravencry

[Willallison]

Attaboy .....
Without putting too much thought into it, my 1st reaction would be to go for a flat bottomed punt. It would plane at the lowest speed, have the greatest load carrying capability and be by far the easiest to build. It might get a bit hairy at 20 knots, but if you could settle for 15 it would certainly be worth considering

[PAR]

The punt shape or better a classic jon boat would be suitable, though it'll pound if driven too hard. It'll climb up quickly and with moderate power, if you keep it narrow.

I'd be inclined to lean toward a Garvey shape if not a conventional pointy bow, for your needs.

Considering you design skills, I'd still strongly recommend a set of plans. FreeShip and other low cost or free software packages will draw up a very efficient or inefficient shapes, depending on what you input. Unfortunately, it doesn't tell you the difference between the good ones and the bad, nor does it handle any of the structural requirements. This is where the design skills come to play. In other words, there's no substitute (or software) for understanding the concepts, principles and dynamics involved.

[tom28571]

I agree with the others. This is not a good starting point. Best to throw it out and look elsewhere for plans. There are several sources for free plans for situations like yours. The UN has some plans for fishing boats that would be suitable. These can be constructed of plywood or planks.

http://www.craftacraft.com/fao_fishing_boat_designs_v_bottom_boats_of_planked_and_plywood_construction

Garveys are too wet for me. I'd prefer something that can turn a bit of water up forward. On a river, a flat bottom can work out just fine. What you have to do is force the bow down. It naturally wants to lift up and that is what causes most of its pounding tendencies. Below is a link to a boat that impresses me. It is flat bottom but regularly makes long runs in the Pacific off California. It's worth some serious study. If you blow up one of the photos and look carefully at the trim tab on the stern, you can see what lifts the stern and drives the bow down. I've had some discussions with Brad, the designer, and think he has found a reasonable solution that will also work well for you, although you need a larger size to carry the loads you want. I use similar technology as part of some of my designs. This system also makes for more stable behavior for varying loads and is less sensitive to fore and aft placement of loads.

http://www.oceanskiffjournal.com/index.php/osj/1EMPS/610/P0/

110hp should give you 20mph with this boat if it is built with a good flattish bottom. You don't want to run at wide open throttle, so 125 to 150 is more likely to work better if that big load is hauled a lot. At lighter loads, the 110 would be more reasonable in fuel use. I'd give it a pointed bow with some flare and upsweep and effective spray deflecting rails on the sides. A waterline length of 23' to 25' and waterline beam of 8' should be about right.

[daiquiri]

I think you could find some inspiration (and understand better the appropriate hull form for your needs) at this page:
http://www.working-boats.co.uk/

[lewisboats]

My thought is....Panga or Panga like. Add a bit of a hook...say 3/4" to the aft 6 ft of the bottom to act as a trim tab to keep the nose down. Look at how a SkiffAmerica20 planes nice and flat...Adams has 3/4" hook and still gets about 25 mph out of a 25 hp. As far as engine size...You should have more engine than you really need...so you aren't constantly running it maxed out...it'll last much longer and give you much less trouble, plus you have some in reserve to counter a heavy current, heavy passengers etc.

[Ravencry]

30465
This might be a better design.
It will hold 2.6tons at a 13 inch draft. Its 29feet long and has around an 8foot beam. I am thinking of around a 115hp or 150hp outboard.

[tom28571]

30465
This might be a better design.
It will hold 2.6tons at a 13 inch draft. Its 29feet long and has around an 8foot beam. I am thinking of around a 115hp or 150hp outboard.

It will never make the speed you asked for with that load and power.

[Ravencry]

What must I do!!!!!!! =(


=)

[lewisboats]

Here...something like this: 28.5 ft long, 2250 lbs cap, 7.71 ft beam 125-150 hp about 8" draft.
Shallow vee, decent planning performance, shallow draft and good forward wave cutting with the forefoot. 1/2" ply x 2 for the bottom plus framing, 1/2" for the sides. Basically a Panga...used and abused for many a decade all over the Carib...can't go wrong. Use 8" 1x butt blocks at all joints, epoxy if you can get it, framing with chine logs (internal) and a bit of FG tape to seal the edges.

Steve

[tom28571]

Lewis,

I think the form is ok and well suited to what raven wants. Certainly easier to build than the one he shows. Don't think it can carry the loads he will have at the speeds he wants though. 12 passengers are likely to have baggage and other gear plus maybe a few animals to transport along the river. His earlier guess of total displacement at 5500# might be realistic and this hull probably won't support that while planing at 20kts. It needs more bottom which means more beam. Better input of real needs and conditions are needed to refine it. If these 12 people are tourists, You gotta figure that they may move about to look at stuff on one side or the other and that needs more beam for stability also.

If the boat is going to need to load and offload on river banks, it would do well to have a pram style bow with a drop ramp. This design can have that without much change.

[Ravencry]

30486 30487First off, Thanks for the suggestions, this is helping me learn a lot and get a better Idea of what I can get away with. A basic trip would look like this: When a group comes in from the states I will try to keep the group below 8 people. Add a two or three translators and my self. I work with volunteers that come to help the Indigenous that live on the rivers. From Iquitos the closest group is the Yagua. Their closest village is around 50 miles down river on the Amazon. The farthest villages what we have people at are around 300 miles Away, one-way. My objective in travel is to get them there in a timely fashion. Most people in the US can not get off work for more that 10 or 12 days. That means One day of travel from the US, another to get to Iquitos and then another by river, and then back. Half your time is spent in travel and not helping the people. We are currently having to hire a boat and driver. This boat is a Fugimori, pictures above, This aluminum boat has a 60hp 2-stroke yamaha. With 11 people, luggage and 160gallons of gas we get a wopping, 15mph at full blast. The last trip was 18hrs long at 15mph avg. and was 280 miles long. We used over 135 gallons of gas. I have around $20,000 that was graciously donated to get a boat and motor, this will mostly go into the motor. I am just trying to be a good steward of that money. You guys are helping me do that, so I really appreciate it.

[Ravencry]

30488
Here is a fugimori that has a big motor on the back, there is to much spray to see how many horse power is there but I am sure it is a lot.
I can get a Fugimori used for around $1000. But I am not sure that it would be worth it. If I got my own make using a good design it would probably same me money in the end. Thanks again, Ravencry

[tom28571]

30488
Here is a fugimori that has a big motor on the back, there is to much spray to see how many horse power is there but I am sure it is a lot.
I can get a Fugimori used for around $1000. But I am not sure that it would be worth it. If I got my own make using a good design it would probably same me money in the end. Thanks again, Ravencry

This would have been great information to have from the start. Loading is not as great as I thought it might be but heavy enough to be serious for a small boat.

People in dugouts must love to see that Fugimori coming. Looks like fun for about an hour and then not so much fun after that. That wake looks like poor fuel mileage also. Your aluminum boat doesn't sound too bad on either speed or fuel use but can probably be improved on in both respects.

[Ravencry]

Check the stats on this boat. Let me know what you think. I obviously would not be able to purchase this boat, but it gives me hope. copy and past the web address.

www.wooldridgeboats.com/brochures/26F_SSPilothouse_PD_Single115EvinrudesWeb.pdf[/url]

[tom28571]

Check the stats on this boat. Let me know what you think. I obviously would not be able to purchase this boat, but it gives me hope. copy and past the web address.

www.wooldridgeboats.com/brochures/26F_SSPilothouse_PD_Single115EvinrudesWeb.pdf[/url]

Raven,

Now you have found someone who knows how to make a boat haul a load at speed on lower power engines. However, notice in the video that in the first part, the trim angle is pretty high and not as high later with the same load. That is because they moved the barrels further forward and when they increased the load, they placed them as far forward as possible. As I said in the beginning, your boat needs a large footprint on the water and this footprint must be of high lift character, meaning pretty flat.

Moving the weight forward trims the boat down and exposes more bottom area to the supporting water. It's not rocket science but it is important. None of the drawings you offered show enough regard for these ideas. A transom trim tab like that shown on The Good Skiff in my first post would help with boat trim.

These boats in the larger sizes would be great for your needs. I am not crazy about garveys but on calm rivers they would probably be fine. They are not too wet at speed but will wet the crew at speeds just above displacement speed. That flat forward bottom smacks the water and throws it up so wind can send it into the cockpit. They are drier at higher speed because the boat is gone before the spray can come back on you.

[baeckmo]

I am surprized that nowhere in this forum I have seen reference to the TMB series 62 hull shape! In particular, it would be a perfect basis for a boat with your specification. There simply is no other planing hull that has generated so much "planing knowledge" as this one. There is a "library full" of tests in various configurations and with a variety of spray-rails, bottom rise angles and wedges here and there.

In its basic shape it has a remarkably low resistance and is not too sensitive to mass center variations. In addition, it is from the beginning designed to be built in sheet material, with all surfaces of single curvature. With its rather full bow, it has better behaviour in a following sea than many of the "flashier" hulls, that are prone to broaching violently. This also makes it a good choice for applications powered by water jets, surface propellers or "long-tail" drives, where the thrust line is high, or where you just have a bunch of people up front.

For someone, who is taking his (her?) first steps into the design/building djungle it is wise to use as much as possible of official, verified know-how. This way, you always have an established benchmark to compare your own achievements with.

The basic sections plan for the mother model occurs in many textbooks, "Principles of Naval Architecture", edited by John Comstock SNAME, is one example. If you cannot find a suitable reference, mail me back and I will send the plan; I don't think anybody would start arguing about "immaterial rights" here.....!

[apex1]

This one:

[baeckmo]

Hi, that's quick enough, and exactly the one. Though maybe the Clement/Blount paper is more directly applicable for Ravencry's job. The parent model, no 4667-1, sized to Lp~8.5 m would carry the load easily. Just have to check static stability with people moving around....

Personally, I would use the DNV 15 m rule: "Heeling less than 12 degr. with a load corresponding to the max pax number, with surface load 300 kg/m2, displaced as far as possible to the ships side. In this condition, the freeboard shall not be less than 0.2 m anywhere". Better suggestions anyone?

[Ad Hoc]

Plenty more here too:
http://www.boatdesign.net/forums/boat-design/anyone-have-copy-1964-1976-savitsky-papers-10970.html

As for heeling, tricky. On a small boat i wouldn't have it greater than 10degrees, but you'd need to see how much reserve stability there is too, once heeled

[BWD]

I think unless you have free labor and make it of local materials, any boat that size will cost you more than $1000 to build, especially if there is any paid design or labor in it. No? Time to build is an issue also.

So the fugimori for $1000 sounds the best bet so far.
It's there.
It works in the area you will navigate.
Crew and any local passengers are familiar with it.
Locals may be more likely to see it as a local boat, not an outsider or as much of a target for theft, (or for mixed feelings).

I bet a suitable motor to plane it can be had for under $10000. That would leave you >$9000 for fuel, repairs, and supplies to help with your mission(s).

If these boats are built in the area, perhaps you could just get a builder to make one a bit wider to make it plane better, and/or add some spray rails. The cheapest/best might be to get a "fugimori" with a 120-150hp motor, and add spray rails.
Rails keep the spray from getting you all wet and can also make it plane better.

I understand you are not wild about the fugimori, but if it will do the job, it might be ok. would not plan on delving deep into boat design or consulting NAs if I were in your shoes. If not the fugimori, find a big panga somewhere.

Whatever you do, the trips you are talking about are going to be long, in any boat. You could easily spend 4 times the money and fuel to get a trip only marginally easier, in a bigger and supposedly "nicer" boat. Just my 2 cents...

[Loveofsea]

How cool Tom~!

I just happened to stop by here and saw your link to the article about my skiff. I'm still running these seas like you wouldn't believe:)

Ravencry,

I have had a number of engines on the skiff and i do meticulous logging of my miles traveled and gallons burned--i know my milage down to 3 decimal points. I have ued Merc 75HP 2-stroke, a couple of 90HP2-stroke, a 90HP 4-stroke Honda, a 100HP Yamaha 4-stroke and most recently a 115HP Merc Optimax 2-stroke. The opti gets better milage than any of the other engines, hands down. I get .2NM better milage with the Opti than the Yamaha. Over the course of a trip, that saves a couple of gallons over the yamaha, for the same weight! Hope this helps...

BTW, I bet it's fun to make a run like that!

[Fanie]

Tourist sometimes are like sheep. The first time they see something beside the boat all 50 of them are going to run to the same side to see, you have to make sure the boat is not going to go over.

Personally I would consider a catamaran hull, 12m long and 6m wide. It will offer a lot of passenger space and stability. Twin motors would make it more maneuverable and if one motor develops a problem the other will save the day. A 60hp motor per hull will have it fly.

[apex1]

Tourist sometimes are like sheep. The first time they see something beside the boat all 50 of them are going to run to the same side to see, you have to make sure the boat is not going to go over.

Personally I would consider a catamaran hull, 1

Fanie he is transporting people on the Amazon river. They are NGO volunteers. A cat is not the right solution for him as we found out on another thread.

[Ilan Voyager]

The boat is not the problem, the actual one Fugimori will do the job at the cheapest price and the least effort.

The true problem is the the 60 HP Yamaha outboard, probably from the Enduro series. Very thirsty boy, it can be only beaten by Australians drinking beer. This engine has one of the worst specific consumptions of the 2 stroke history and at full open throttle with his little 60 HP it's not far from 350-400gr/HP/hour if the carbs are a bit worn. To worn a Yam carburator is very easy; dismantle it once without care as it's done in most latin american countries. Or forget to grease the choke.

I would keep the money for 4 stroke outboards and keep them at 75-80% of the max power close to the maximal torque and the best specific consumption lets say about 220-235 gr/HP/hour. It´s 40 % better specific consumption.

That means a 100 HP 4 strokes with injection, or 2*50 HP. That have some advantages: the 50 HP are very light, simple with carbs and quiet, and you have 2 engines... The Mercury or the Yamaha 50 HP are equivalent. Lone "con" the consumption is not as good as with the injection but far better than the 2 Strokes. The lone Enduro Yamaha with a decent consumption is the 85 HP 3 cylinders, but needs a good mechanic as the carbs are pretty complex. Some trials of propellers would be a good idea...generally the propellers have too much or not enough pitch on this kind of boats, as everybody use the propeller sold with the outboard regardless of the size and weight of the boat. I live in a third world country, and I know how the boats are not tuned or worst detuned... A bow pointing to the sky is useless so keeping the boat at a 4 to 6 degrees is the most easy way to save money and to get speed.

Having to build a faster boat is expensive...keep the money for the people who need it.

[Ilan Voyager]

Baeckmo, thanks for reminding the evidence in boat design...Apex thanks for the PDF, very useful. What's this rage of trying to design with some freeware when there are plenty of good and proven plans for a few bucks? a very small and tiny fraction of the price of the boats...

[Ilan Voyager]

Ravencry, if you need a really fast transportation on river or lake, ie flat water by true necessity like ambulance etc... go to the hovercraft. Very different story but very efficient. No boat at equal power can follow an hovercraft on flat water... It has its cons also (noise mainly), but low waters in dry season are not more a problem. The French army uses hovercrafts in French Guyana.

The technology is simple, the construction uses common materials and it´s powered by a car engine. The Duratec 4 in line engines from Ford are good candidates (the 2.3L is used by all the latin american Rangers so the spare parts are available, and weights less than 120 kg naked) apart the Suzuki and Subaru (very exotic in South America)

To give you an idea of the thing
http://www.hovercraft.com/content/index.php?main_page=index&cPath=35_55

At 80 bucks is a good idea to buy the plans to examine them.

[apex1]

Ravencry, if you need a really fast transportation on river or lake, ie flat water by true necessity like ambulance etc... go to the hovercraft. Very different story but very efficient. No boat at equal power can follow an hovercraft on flat water... It has its cons also (noise mainly), but low waters in dry season are not more a problem. The French army uses hovercrafts in French Guyana.

The technology is simple, the construction uses common materials and it´s powered by a car engine. The Duratec 4 in line engines from Ford are good candidates (the 2.3L is used by all the latin american Rangers so the spare parts are available, and weights less than 120 kg naked) apart the Suzuki and Subaru (very exotic in South America)

To give you an idea of the thing
http://www.hovercraft.com/content/index.php?main_page=index&cPath=35_55

At 80 bucks is a good idea to buy the plans to examine them.

Thanks Ilan
we had the Hovercraft discussion here on his first thread (and I was one of the supporters of that solution)

http://www.boatdesign.net/forums/boat-design/amazon-river-loadum-up-26486.html

Regards
Richard

[Ilan Voyager]

Apex, I did not know this interesting thread...worth to read it. So I suggested an already known solution.

Yes, for "fast" transportation an hovercraft in river conditions is unbeatable. I have a Colombian friend working on the problem of river transportation and it appears that hovercraft is the solution for light loads; it can be built locally ( complete with engine etc...) for less that the price of the Yamaha 150 HP outboard engine moving the same payload boat.

The main problem in rivers is the propeller and transmission that are broken regularly by hitting something...it's very expensive and you can add that the carbureted 2S are very thirsty, and the 4S too expensive. Trials have been made with marine diesels with no good economical results.

Another solution is the flat boat powered by car engines and aerial propellers; it has also its pros and cons.

I think the main problem is economics: marine engines are very expensive and have to be bought in dollars, spare parts are out of reach of most people.

On the other side you can find in Latin America a lot of reliable car engines that can be used on a small boat or hovercraft like the old Nissan Tsuru model, Chevy, Ford Ranger and others, easy and "cheap" to maintain.

[Village_Idiot]

Here is another data point...

I'm running a mod-V flat-bottom aluminum boat (jon boat style), 26 feet in length, 60-inch bottom width. With a 4-stroke 115hp Mercury outboard, it will plane with 12 people aboard and run about 30mph. However, the boat does have a pocket tunnel. I suspect with a full hull you could easily achieve 30 knots sustained. Also, it has a custom propeller which will make a difference. Despite its 60-inch beam, it is very stable, owing to its flat bottom. Lightly loaded, the same boat will run close to 40mph.

For your needs, in a relatively calm river, you need a flat bottom with square chines. As others have pointed out, the Fugimori may be your best bet with a modern FI 150hp outboard running a well-tuned stainless steel prop. If boat proves stern-heavy, you can add floatation pods to the transom, a practice becoming more common among jon boat builders. If you need to build, the Panga style is not a bad one.

[Fanie]

Fanie he is transporting people on the Amazon river. They are NGO volunteers. A cat is not the right solution for him as we found out on another thread.
Sorry, I'm curious for the reason why not. Please point me to where I can read or explain the reason. Thank you.

[apex1]

For your needs, in a relatively calm river,

That was a good one mate!:D


I recommend to read the thread I posted above!

Same recommendation for Fanie. And do you remember your own thread Fanie? http://www.boatdesign.net/forums/multihulls/multihull-fast-flowing-water-28116.html

Regards
Richard

[Ilan Voyager]

A Fugimori is overpowered with 150 ponies...over 100 HP you're making foam and spray, it will be a waste of gas and money. A panga (we have many here) is not a very good boat in sea but a very good one in flat waters; a 26 feet takes 6 to 8 people with 85-100 HP.

If you want to save the transmission is better to have an aluminum propeller; cheap, easy to repair with a simple LPG torch and zinc alloy, easy also to tune by 1/3 to 1/2 inch of pitch. When it hits something it breaks before destroying the pinions of the transmission. Ok it's better to have some spare propellers...

The problem of expensive outboards on river boats could be -maybe- resolved with aerial propellers and car engines. I see some advantages (and inconveniences) also to this solution; mainly economical. A wood propeller is not very difficult to make and equilibrate, the transmission may be made with industrial and common elements, the complete engine can be found in a junkyard.

Cats are rather fragile on river among rocks, trunks and other obstacles; flat boats stand more abuse, and are simpler to build and repair.

[Village_Idiot]

That was a good one mate!:D


I recommend to read the thread I posted above!

Same recommendation for Fanie. And do you remember your own thread Fanie? http://www.boatdesign.net/forums/multihulls/multihull-fast-flowing-water-28116.html

Regards
Richard

Yes, I should have qualified "relatively calm" - what I meant was waters with waves typically less than three feet.

I read the loadem up thread and have not really changed my opinion, other than perhaps Ravencry should find a 30'-33' Fugimori and outfit it with twin 90hp Yamaha two-strokes - they are carbed and, although they will use more fuel, they will likely be cheaper to maintain in the long run.

I regularly run a river here that typically has 3-4mph current, plenty of snags and sandbars that change positions overnight. That is why I run a pocket tunnel. Although the water is murky, with visibility less than six inches, the river tells its tales and I don't hit anything with the prop that I can't see. I should caveat this with the fact that I run a raised helm so I have good visibility which is key for running dangerous rivers.

[Village_Idiot]

A Fugimori is overpowered with 150 ponies...over 100 HP you're making foam and spray, it will be a waste of gas and money. A panga (we have many here) is not a very good boat in sea but a very good one in flat waters; a 26 feet takes 6 to 8 people with 85-100 HP.

If you want to save the transmission is better to have an aluminum propeller; cheap, easy to repair with a simple LPG torch and zinc alloy, easy also to tune by 1/3 to 1/2 inch of pitch. When it hits something it breaks before destroying the pinions of the transmission. Ok it's better to have some spare propellers...

The problem of expensive outboards on river boats could be -maybe- resolved with aerial propellers and car engines. I see some advantages (and inconveniences) also to this solution; mainly economical. A wood propeller is not very difficult to make and equilibrate, the transmission may be made with industrial and common elements, the complete engine can be found in a junkyard.

Cats are rather fragile on river among rocks, trunks and other obstacles; flat boats stand more abuse, and are simpler to build and repair.

I've changed my opinion to a larger Fujimori with twin 90hp Yamaha two-stroke motors. As I said earlier, I am running 115hp on a 26-foot aluminum and the power is usually not wasted. It runs close to 40mph lightly-loaded, and 30mph loaded with 12 people. Any less HP and it would likely not plane with 12 people, especially with a standard prop.

I have run many different boats on rivers over the last 20 years. I have bent/broke two propeller shafts and both of those have been with aluminum props. Now I only run stainless steel props on rivers, but I also run them with (pocket) tunnel hulls. When running on plane, I run through six inches of water, and four inches over short distances (sandbars). It is very hard to hit something with a propeller with a well-designed tunnel hull unless you are not paying attention. The river I run in has visibility less than six inches, but the river's surface and current will tell you where snags, sandbars, etc. are hiding when they are less than a foot from the surface. Also, to my knowledge, know one makes or modifies aluminum propellers that will run efficiently in a tunnel hull. When not on plane, the boat is running slow enough that the rubber/delrin hub on the SS prop takes the hit rather than the gearcase.

Since the OP's requirement is for a heavy payload, I don't think air-powered machines will fill the bill, at least not without a LOT of HP which equals a LOT of fuel. Flat-bottomed aluminum is the way to go.

[Ilan Voyager]

Village;

-The Yamaha sold in Latin America are of the Enduro Line, which are very different from those sold in the States. Practically the lone common feature is the logo Yamaha. The consumption and emissions have nothing in common also. The 2S Enduro have a TBO (time before overhaul) of 1000-1200 hours, that's about one half of the TBO of any 4S.

We use here these Yamaha Enduro so we have direct facts from experience and the difference of consumption is so high that in ONE year (800 hours about) you have over-spent in gas and oil almost the price of a brand new 4S of similar power...

I've spent many hours in meetings with the authorities 11 years ago to convince the fishermen and dive shops to switch to the 4S mainly because of pollution and protection of the reef barrier...We heard a lot of protestations but some switched and after 4 years everybody was using 4S as the advantages are blatantly evident.

The Enduros and small 4S sold in Mexico have not nice amenities like delrin and such transmission savers...directly bolted on the shaft in the old fashion way. As the boats here have to beach 3 or 4 times a days you can imagine the results of hitting with a pretty strong inox propeller ... the pinions of the transmission lose the teeth and sometimes the carters are broken.

Think that in Latin America, where the consumer is not protected and has no way to sue in court (the judges are in permanent sale to the best bidder) the quality of the goods you can buy cannot be compared to the quality of a similar good bought in a First World Country. For example the best warranty that gives you Yamaha in Mexico is 6 months or 300 hours; in clear NOTHING.

The Fugimori are very similar to the boats used in Mexico made by IMEMSA and others, and in Colombia by Eduardoño. A lot of people try to get more speed on such boats putting "big" engines with no results; I made the demonstration 8 years ago with 2 identical 26 feet IMEMSA loaded with the same weight (8 divers) one with a 100 HP 4S and the other with a 150 HP 2S. The difference of speed was minimal (less than 2.5 knots) but the consumption of the 2S was simply almost twice the consumption of the 4S...

About air screws; I can say that a ducted 5 blades propeller is a very powerful fan and moves big loads. That have succesfully been tried in the French Navy about 14 years ago for use in Central Africa.
There are also Russian heavy hovercrafts with no need of high speeds used in Siberia on the rivers all year around (water, snow and ice) and the power used has nothing tremendous.
These kind of propellers have nothing comparable with a plane propeller. The efficiency is rather good.

In Latin America is simpler to go to polyester, almost nobody is qualified for aluminum. Simply too expensive.

[apex1]

I thought it was almost ALL said in the "Amazon" thread. And for sure the most economic solution IS a hovercraft. But Ravencry had some arguments against that. Probably the boat he showed us in the first post is a sensible vessel for the use intended, when properly powered of course.

[Ilan Voyager]

Yes Apex almost every thing has been said about the subject. Like you, and my Colombian friend, I think that for fast transportation on river, navigable or not, the hovercraft is the best option. Some other people, in Siberia for example, share this opinion.

And for powering a "classical" boat on river a 4S outboard is a good option. I didn't talk about the 2S with direct injection like the Mercury Optimax and the Evinrude Etec as I have not first hand reports about them. It seems that the Optimax has some problems of reliability but there is not reliable statistics nor reports.

I'm afraid that these sophisticated 2S are a bit over the abilities of the local mechanics and local gas quality. A computer is needed for any job on them. It's the same problem with the 4S, thus I have proposed the idea of 2 outboards of 50-60 HP as these engines are "carbureted" and as simple as a small motorcycle. Very reliable also; a friend of mine has a Mercury 50 HP with more than 2400 hours running as strong as the first day with simple maintenance. I must add that this friend knows only 2 positions on the throttle; iddle and WOT. That simplifies the tuning of the carburetors...

[apex1]

I must add that this friend knows only 2 positions on the throttle; iddle and WOT. That simplifies the tuning of the carburetors...

Did´nt know there are two strokes with a "dual system" throttle on the market...:D

[Village_Idiot]

If the Fujimori is similar to the Panga (IMEMSA), then that may be the most sensible way to go.

Perhaps the solution is to run two lightly loaded Fujimori boats, each with a 60hp 4S "Bigfoot" outboard. Again, I would be very careful not to underestimate the significance that the design of the propeller itself can lend to performance.

[Ilan Voyager]

Idiot, your statement is totally illogical, like the former other statements:

-1 You have to use the good length of foot as required fot the design. As nobody in the forum, except Ravencry, knows what length is asked by the Fugimori, you can't state that a bigfoot is required.

-2 With 60 HP a Fugimori even lightly loaded won't go far over 15 mph. Maybe 17 or 18 mph if very light. Too much wetted surface as the boat is almost flat, and the wetted surface changes very little with the weight, so the speed. And 15 knots is not a good speed for a such boat. This kind of boat begins to plane at about 10-11 knots and will be fully planing at 16-17 knots.

The goal is to load the boat to his designed weight and to make a decision of speed. 15mph or 13 knots IS NOT ENOUGH speed to take full advantage of planing after the hump of drag in transitional regime. You need to go at least at 16-17 knots and that won't ask for a lot more gas consumption...

At 60 HP the poor little engine is screaming at 100% of its power; it won't last. If you want that an engine lasts at the full potential of its TBO, it must run at 75-80% of its max power. Interesting fact also it's where the torque is at the maximal value and the specific consumption at its best value.

So let's make some very basical powering engineering.

1/ Asking the designed displacement of the boat to the shipyard, and maybe they have the drag values.
2/ Calculate the optimal dead load and its center of gravity so the boat has a good LCG, convenient for the target speed.
3/ Calculate the power needed for the target speed and for the planing boats the power needed to go through the drag hump. In clear to get the boat out of the hole.
4/ Examination of the specific consumptions of the different suitable engines. A fact has to be taken in account; outboards have too small propellers, specially when you go to the higher powers. Morality the efficiency of the propeller of a 60 HP is better that the efficiency of the propeller of a 120 HP as the diameter changes very little.
5/ Other hard fact we are in the rain forest; a carburator is easier to maintain and fix than injection. More if the gas is of low quality. And it appears also that in small engines the injection does not improve really the specific consumption.
6/ That leaves one good candidate:
The FT60BETL 60HP 4S 120kg 4 carburators 19.5L hour at WOT 244gr/HP/h at WOT, 225gr/HP/h at 75-80%.
For comparison the two strokes E60HMHDL 60HP 2S 105kg carburators 25.5L hour 319gr/HP/h burns 31 % more gas for the same power!!!!
7/ the 115 HP is with injection and the specific consumption is higher than the 60 HP. Normal its propeller has a too small diameter, the efficiency is lower. It weights 190 kg.
8/ 2*60HP weight 240 Kg only 50 kg more than the 115HP.
9/ Conclusion: it's very probable that the 2*60HP 4 strokes is the winner combination.
a/each engine weights 120 kg, easy to take out and move.
b/very but very simple engines and very strong.
c/in remote places 2 engines is not a luxury, it's the insurance you arrive.
d/used at 75%, so 90HP the consumption per hour will be around 27 liters/hours, and you can compare with the 60 HP 2 strokes 25.5 liters/hours, but the speed won't be no more 13 knots but 17 or 18 knots. Look know at the total consumption; 18 hours*25.5l= 459 liters with the 2S, 14 hours*27= 378 liters, so 80 liters of gas less...Morality you can go at 17 knots consuming 20% less gas with 2*60HP 4S than 13 knots with the 60HP 2S for the same travel...Just a bit less luggage to keep the weight good.

Now I have to do some true engineering for repowering a 36 feet, so I go back to work.