Propulsion general questions for heavy use on 30ft power cat.

Discussion in 'Propulsion' started by xellz, Dec 29, 2018.

  1. xellz
    Joined: Jul 2017
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    Location: Japan

    xellz Junior Member

    Some might saw my old post about making an electric boat and i actually bought plans for Jazz30 by Richard Woods more than a year ago. But due to various reasons, it took a lot longer to complete plans. Right now only some minor questions left, so i will be getting ready for building during January/February.

    Before i start or during early stages i need to make final decision on propulsion. I'm trying to go with electric, but it's quite a big wall to get over. First of all, no ready solution that makes sense is available.

    First expected use, for now i'm using 7.7m LWL mono with 150hp inboard diesel. This gave me some actual numbers. For 6-8month over 200h per month, 1-2month during winter less than 100h, the rest is between 100-200h. I.e. about 2000h per year. Majority of trips are short distance, fishing spots are close, within several km of each other, low speed is acceptable. The furthest trip is 60km one way, but it's for dropping off large catch only. Speed below 10kt majority of time, but going occasionally low-middle teens is required.

    Electric has obvious advantage in maintenance, no regular oil, parts changes, no saltwater intake for cooling. But i don't want to completely ignore other propulsion systems because for electric bank loan will be most likely necessary, big compromise in almost every regard. For comparison purposes, electric propulsion initial cost i estimate somewhere in the 60-80.000$, 2x15kW motors and based on Kokam NMC battery bank 60-70kW. More expenses for shore charging and small onboard genset for emergnecy.

    1. Petrol 20-30hp outboards. About 8.000$ initial cost, but short maintenance cycle and petrol always has road tax included. Many references available for maintenance cost, but any input is welcome.

    2. Dtorque 111, 50hp diesel outboard supported by Yanmar. New and unknown, more than i need. But extra speed can be welcome in good weather. 250h for oil, filters, impeller, 500h for other expendables. Low fuel consumption, diesel for boats does not include road tax and is considerably more cheaper than petrol. Initial price is hefty, about 80.000$ for 2.

    3. 20-30hp Yanmar inboards. Richard didn't confirm yet if inboard diesel can be used. But if can be, tight fit, maintenance will be a pain to do. However from every point it looks like best for my needs. 35.000-40.000$

    4. Can ICE engine maintenance cycle stretched a bit, if engines are often in idle or at low load? By how much? Current old heavy duty 150hp yanmar i was told to watch oil condition and based on condition change. But rough estimation was 200-350h or once a year. I can't find manual for it, so going with boat mechanic recommendations.


    What would you choose if had to use boat in my conditions mainly for sport fishing chartering and commercial fishing in absence of customers? Why? I would also add that while i might be good at fishing, i'm complete novice when it comes to ICE engines. Please share your experience or opinions.
     
  2. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    Well, sounds like mostly day trips? If so I'd forget the diesel idea. Diesels are great for long distance cruising but for relatively short hops they're expensive and can be heavy. Inboards on a boat such as you contemplate can as you know be difficult to maintain and work on. Electric? I have no idea. I've never been on an electric powered boat but based on what you wrote the cost is prohibitive and I'd be concerned about operating in a salt water environment. You're right that the electric motors would not be in the water but there is an issue with salt air/condensation.

    That leaves the outboard option. First, outboards are relatively inexpensive. They're easy to maintain. You can keep them out of the water when the boat is docked/anchored. For the speeds you want to travel I'd suggest you look into a pair of high thrust outboards. A few firms manufacture make them but I'm partial to Yamaha. I own a T9.9 Yamaha and absolutely love it. I use it as a trolling motor and for low speed cruising. For your boat a pair of T25's (25 horsepower) would probably be more appropriate but you'd need to look into that. Need more power? They make them up to 60 horsepower but based on my experience you would not need that much thrust. The idea behind high thrust outboards is that they are geared down and swing a large prop. The prop on my 9.9 is almost 12 inches in diameter. The idea is not to go really fast. The idea is to push a heavy load and push hard. My small cruiser is only 25.5' LOA and 10.5' wide and about 5 tons. That little T9.9 will push it around all day at displacement speeds. When the wind and current picks up I just throttle up a bit. The t9.9 has always kept me on course. You might want to look into high thrust outboards.

    As for maintenance, a lot of idling is actually harder on an engine than running at speed. That said, you'd be better off changing oil more frequently with a lot of idle/low speed operation. I'm not sure if the T25's have an oil filter but suspect that they do. Either way you should be able to change out oil with the boat on the water provided you work carefully. Once the engine is warmed up you can insert a small tube connected to an oil change suction pump. You suction the oil out of the engine and simply replace it. No big deal. Just be sure to keep oil out of the water and don't drop the oil filler cap or dipstick into the drink! One last thing. Always, always use good synthetic oils of the proper viscosity.
     
    Last edited: Dec 29, 2018
  3. fallguy
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    fallguy Senior Member

    Electric upfront is nuts and you might spend more time managing electrics than fishing.

    The Jazz 30 hulls are narrow for inboards. Sorry; you'll hate upkeep.

    The ob diesels are well over a hundred pounds heavier per than the Yamaha 70s. They are also going to cost you major bucks. The design is unproven and uses two crankshafts. Not a fan for your application.

    The motors you cite are all underpowered for the Jazz30. The Skoota 32dm I am building is getting two F70 Yamahas. Cruise will be about 10 mph/knots, you pick. It will burn 1.6gph or so. The engine is super light and well tested and it would be my preferred power on the Jazz30. If RW says it is too much, drop to his specified maximum hp.

    If you go with Glendining controls; they have a bump feature that gives you 15 rpm increments for trolling. Those engines will sip trolling.

    Building a boat is plenty tough. Make the engines easy. Get them rigged and propped and get to fishing.

    The other thing about a couple F70s is the local authorities will take you more seriously than a couple small 20s for a charter vessel. How would you like to be 60km out and get a tsunami warning in a 10knot max speed rig? You basically are forced to beach asap. What about a gale even?

    The Jazz needs some power. You'll be sorry you don't.
     
  4. xellz
    Joined: Jul 2017
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    xellz Junior Member

    Thanks for input everyone, if only i could try out everything myself. But have to choose only based on data i can find.
    Especially helpful was comment on oil change on water. If it's indeed can be done without too much risk, major downside of petrol outboard will be gone.

    Power recommendations are from Richard Woods. Jazz30 is quite close to his Skoota28, Jazz30 is lighter with less windage and slightly longer hulls. Twin 20hp outboards should be sufficient for low teens cruising speeds even fully loaded.

    Why i even considered diesel outboards and inboards is major difference in fuel price. But you are right, i rather not deal with inboards in Jazz30 if i can avoid it. I have 150hp, 600kg+ diesel in small mono now, not fun at all. At current prices, diesel for marine use (no road tax) is at about 180usd for 200l delivered to island compared to roughly 270usd for petrol. Petrol outboards with about 2000h yearly will also bring major maintenance cost and downtime. GPS anchor system is already readily available for petrol outboards, that would be big help. I really dislike small sail that is used to point the boat into the waves while drifting. Managing electric system should be a lot less time consuming than ICE. Propulsion system will be designed by company with some experience in marine electric systems, several options available. But for reliable work over long period quality components are necessary and thus quite serious price tag. Quite difficult to accurately estimate when it will break even compared to petrol outboards since i didn't use them myself. But for now, roughly 3000-3500h without considering downtime for maintenance.

    Wast majority of spots are within 10km from island. Island located on the edge of gigantic caldera roughly 20km wide, so all points are close. In my current mono i'm mostly going at 6kt, over it it's already starting to climb on a plane. If conditions allow, 12-13kt quite fuel efficient, but most of the time waves and swells are just too big for a safe ride at speed on a small boat.


    Right now what i consider best, most logical option is to prepare for straight shaft electric inboards and rudder mounts and go with petrol outboards for at least a year or two. But the fun factor of electric is pulling me in different direction. Getting out my ideas here kind of helps to sort everything out. A bit too exited that after long waiting time can start moving my ideas from paper to reality.
     
  5. fallguy
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    fallguy Senior Member

    Remember they are semi displacement hulls. It will perform much better in rougher conditions with enough power.

    I am rather surprised RW didn't rate that rig at least to twin 50hps.
     
  6. xellz
    Joined: Jul 2017
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    xellz Junior Member

    Recommended setup is exactly twin 40-60hp with estimated top speed of 21kt with 40 and 25kt with 60hp, cruise at 15-16kt. At low speed don't need much power even in rough conditions, Richard shared his experience with his twin 20hp setup. It's enough for me. For same reason i'm even considering electric, for majority of people speed and range is simply not acceptable, that's not even touching problem of charging.
     
  7. fallguy
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    fallguy Senior Member

    Went on a charter boat on honeymoon. Spent the whole day. Guy had a trawler. He couldn't get us to good fishing grounds; boat too slow. Seals followed is to the fishing grounds. They took our catch. Wife has a picture of me with a 200 pound seal on the end of the line with my salmon in mouth.

    I would recommend going near rated maximums for pax safety, repeat customers. You can always throttle down; not up past the motor rating.

    You asked. I answered.

    F70 Yamaha, same weight as their 60.
     
  8. fallguy
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    fallguy Senior Member

    The other thing to consider is whether the tiny 20hp motor can operate onboard electronics. The alternators on the F70 are small at 17a. I plan to install ignition relays to avoid running down my starter batteries with my helm. Engines on, helm on... vhf only excepted.

    With the smaller engines; double check the electrical output is sufficient for all helm operations, mfds, radar, AP, livewell, actuators, radio, anything else. That boat of yours will probably only run on engine batteries. It would suck to not have enough juice for marine head, etc.
     
  9. Barry
    Joined: Mar 2002
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    Barry Senior Member

    Outboard gas, high thrust Yamaha, would be my choice 50 or 60 hp
    The fuel consumption of the new outboards is quite good. The initial cost is low. Certainly a difference in cost between diesel and gas as far as the cost per litre.
    The process that I would do is this
    Consider the cost of your electric, or diesel inboards, initially and through the longest repower time, ie which configuration will run the longest number of hours before
    the system requires replacement.

    So if you take you 80,000 for electric and in say 10,000 hours you have to replace 40,000 of batteries ( I don't have a clue on battery costs so the 40k might be out to lunch)
    Then to get the boat back into a condition, say the new 40k of batteries to make it attractive to a buyer, several years down the road, this is a cost you should factor in.

    Alternatively pay 15,000 US for a couple of T60's, replace them when they need replacing and for a small amount you can install new engines, for a low cost at the end of your
    boats life.

    When we were between boats, last summer for a couple of months, we chartered on the west coast. The guide was using Suzuki 150's, at the 8000 hour he sold them and installed new ones

    These engines during the guiding months ran at least 4 hours a day planing 32 foot aluminum boats and then 6 to 8 hours trolling on the idle mode
    While the 8000 hour number was a surprise to me, I compared it to our diesels that we have owned, Cummins 370 and Volvo 350's and we did not get this much out of them and the repairs
    were huge, turbos, intercoolers, buying shares in Exxon for oil changes and the like. The guide who had several boats said that he would never consider diesel inboards, but instead every
    few years, he just traded the old ones back to the dealer, and installed new ones.

    In your case, looking at say 80,000 for 10,000 hours, ( a guess as above) then having to replace batteries at big bucks or as compared to up dating cheap outboards is probably the cheapest way to go

    A couple of boats ago, when we had the twin Volvo D-6 350 hp, we were having a bunch of issues, and I considered replacing the engines, and the cost came out to about
    85,000 (less what I could get for the old ones) so we sold the boat. (some other installation problems as well)

    So say your electric configuration for 80,000 gives you 10,000 hours before you have to rebattery for 30 - 40 k, you can easily install new T60 yammys or even cheaper for Suzukis
    at a fraction at the cost for the equivalent hours of service and still have a boat that the new owner does not have to look at a big bill to get the electrical repowered

    On the west coat of NA, a couple of other companies that do water taxi service, lots of hours every day, say that they keep the engines for a season or two, then sell them and buy new.
    Because they are a business, the outboard manufacturer gives them a break in price, so their cost is much lower than retail so when they sell these used to the retail market, the
    differential is not that much. And they have warrantied, new engines

    OP, can you tell us what the breakdown on cost is for the battery component? And how many hours that you might get from a set up? And I would be interested in what the cost is
    to recharge them regularly. ie electric power cost. Lots of discussion on the site, but I don't recall people commenting on the price to recharge batteries?
     
  10. fallguy
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    fallguy Senior Member

    Our electricity costs 6-42 cents a kwh here in middle America.

    Wife has a Tesla and it charges at the 6 cent rate. The car fills at 7kw for 28 miles. The peak rate would cost like $2.80 for the 28 miles. More than gas. The 6 cent rate results in $0.42

    Not sure if Japan has those types of variances, but a big deal on cost.

    The problem with electric is you will require significant consultancy and it will not be simple in such narrow hulls. The narrow hulls are the beauty of the design, but a bit unfriendly for any inboards.
     
  11. xellz
    Joined: Jul 2017
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    xellz Junior Member

    Had some family matters to attend to, now continuing preparations again.

    I'm trying to go electric also because of environmental reasons, whenever possible i'm choosing a route with less imprint. More real use information of electric propulsion in small boats might help others make a similar choice in future. Narrow hulls won't pose much of a problem with electric setup, especially since i won't have short maintenance cycles. Electricity price is roughly 0.25-0.26 cents per kwh, that assuming i won't get commercial pricing, which is still under question.

    Some information on costs, mostly based on Richards Skoota 28 use. So Jazz 30 might need less power. But just in case, this would be worst case scenario.
    With 20hp outboards consumption at 6-8kn 4-5l/h, 5.4-6.75 usd/h, 12kn 7-10l/h 9.45-13.5 usd/h, 16kn 14-16l/h 18.9-21.6 usd/h. With bigger hp outboards 15-16kn will be more efficient.
    Electric power requirement is based on fuel consumption and power curves of outboards 6-8kn 3-5kw/h 0.78-1.3usd/h, 12kn 18-22kw/h 4.68-5.72 usd/h, 16kn 26-30kw/h 6.78-7.8 usd/h.
    If i stick to planned use there should be about 8.000-10.000 usd savings per year in fuel costs and maintenance costs is about 10.000 usd assuming i can do it myself. Batteries should last well over 10 years in normal use, 10.000cycles. Fast charge/discharge can decrease this rating quite a bit, with 2x15kw motors even at full throttle there won't be much stress on batteries. Electric also can attract more customers, but it's quite hard to make a guess here.

    I think i need to learn more about maintenance of outboards, i didn't own one so have almost no clue. Especially when it comes to 200/300h maintenance. Can i do it on the water? How much time it will take? I'm not 100% on prices too. I can't use service of a mechanic either, only in emergency, really expensive calling to the island. Maintenance issues is actually what scares me away most with outboards solution.
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    I'd say in remote locations you might be better off with 2 strokes, preferably from the commercial offerings of Yamaha, Tohatsu etc, unless they aren't sold there any more because of environmental laws. Use more fuel, but the servicing costs less. Should get a long life out of them if you use the best two stroke oils.
     
  13. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Hmmm. Interesting.

    I have a 2004 Mercury 50hp 4 stroke. I took it in for service one time running rough and repaired a service campaign once. The trim and tilt froze one winter; got water and I fixed. It was spendy for the part. Fourteen years, three service incidents. But guess what! 1500+ hours running...yup...the last service call called me astounded and said I was at 1200 hours...probably 400 hours ago.

    If you get 1500 hours without service to your system; write a book....

    ps, the rough running was caused by the campaign issue and they charged me for new plugs and an oil change and missed the campaign...I discovered it omo
     
  14. xellz
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    xellz Junior Member

    You got over 1500h on outboard with only regular oil/filter change? I didn't do this work, so that's why outboards scare me a bit with lots of scheduled maintenance cycles and parts to change, how necessary those changes are i'm not sure. Lets say if i have to change only oil and filters every 100h for 500-1000h or follow exact schedule from manual will add lots of points to outboards solution.

    In case of electric propulsion there is almost no short cycle maintenance, not the outboards. Maintenance is mostly for shaft. Cutlass bearing and dripless PSS shaft seal should last at least for several years. Anodes replacement about 6months and it's rather quick. Depends on electric motor, but if i remember right only bearing grease is necessary every 5000-6000h. There is a large cow farm on the island and it has several big industrial fans, over 10 years they work non-stop and the owner didn't touch them. Outside metal started to fall apart (looks like aluminum, but not sure) in some places due to high exposure to volcanic gases, 2mm normal barbed wire turns to sand in only 1.5year over there.
     

  15. fallguy
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    fallguy Senior Member

    But your engines are in saltwater all the time; so you have to haul out for all that.

    with ob you can trim up and even get out of the barnacles

    My oil changes have been too few I must add.
     
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