outboard power on larger cruising cats

[Steve W]

Stefano, its early days but I expect we will stay inside as much as we can as the boat will be minimally equipped, its been out of the water for years and is bare and while we will add what we need it will be minimal. I expect we will do the Erie canal route which I have done before and,yes, we do need to take the mast down. We should be able to get the motors close behind the aft beam. The boat has long transoms with steps so there is quite a bit of boat behind the beam. As I said before, this has to be an easy install, not necessarily the final install but I suspect by the time we get it home we will know exactly what we need.
Uos, the boat is not mine, it belongs to my son and his girlfriend. The entire aft cabins have been devoted to walk in engine rooms so going with outboards opens up a lot of real estate. We have only spent a couple of days with the boat so what to do with those spaces will evolve as time goes by.

Steve.

 

[UpOnStands]

the long transoms explain the slight increase in overall length from the 13m of the original simpson plan. Should sail well.
how is your time window for the Great Lakes passage?

 

[Zulu40]

I don't run the Yammie 25 dry ever. It starts within 2-3 seconds after being left for up to a fortnight. It may need a squeeze of the fuel bulb if I haven't been to the boat for a while longer.

From my experience it is two stroke that degrades to leave a residue in the carby. If we stick to four strokes then the fuel will be the same as what you have in your car. I run my Yamaha 8 two stroke dry and the little 3.3 when I can remember. I can take about 5 minutes to strip the 3.3s carby - gives me something to fiddle with when cruising. Do it once every two months but I am rather blase about the oil mix.

It may be nice to have the better fuel economy of injectors but I am not sure they are found on the types of outboards that are commonly used to power cats - 9.9 - 30 hp. Looking at the manufacturer websites the Yamaha and Honda range still use carbys. (Up to 50hp high thrust at least)

I have used these four strokes (Honda and Yamaha) for 17 years on Kankama. I once couldn't start the Yammie when I put in dirty fuel dregs. I cleaned it out and sailed on. So don't invert your fuel filling tanks and put an extra filter on (the ones on the outboards are very small) and according to my experience carbys will be very reliable. They have never stuck on a four stroke for me.

And yes Brian. I always fill it up with Premium. I use so little it doesn't make much difference. We go through about 100 litres in months and months of cruising.

cheers

Phil

I was reading about Evinrude 2 strokes having both EFI and oil injection, thats how it will go for modern 2 strokes I think. Pre-mix should be avoided

another thing they have is a trolling mode for fishermen, where there are considerable savings in fuel to be had at low RPM

I wonder if the gear ratios compare, what would be the difference between the thirsty but reliable Yamahas or new tech lightweight Evinrudes ?

 

[Zulu40]

All the best has been said already I think, but what I gather from previous threads is central pod fitments are best avoided as a correct depth is difficult if not impossible to achieve and props often leave the water.

Also from power cat operators if props are not under the keel they are more prone to cavitate especially with bigger engines. The closer hulls are together the more interference drag there is between them, and much of that is aerated water best avoided.

The ideal outboard isnt yet made, if it were it would be around 3:1 ratio, diesel, and 4 blade prop.

One thing Im thinking for power cats, can they do without rudders entirely?

 

[UpOnStands]

For guys running outboards, how much fresh water do you use for flushing them? And do you flush them religiously?
running the garden hose for 5 minutes means a lot of good stuff is lost.

 

[catsketcher]

I have flushed my outboard about 4 times in 8 years - when it was out of the water. I worry a little about the salt in the galleries but some mechanics tell me not to worry - run them for a long time every now and then and I was told it would heat up the interior and help release the salt build up. There is a product called Saltaway or similar but I have never used it. Won't know about anything till I take the water jacket off and I won't do that unless I have to.

cheers

Phil

 

[Steve W]

We have just returned from a grueling4 day trip to florida to prepare the Simpson 13m cat my son and his girlfriend have just bought, 54 hours on the road, the rest preparing the boat for winter and lots of brainstorming, taking measurements and templates for the upcoming conversion to outboard power, I think we have a solid plan for twin Yamaha 25 high thrusts that should work well. We have a good location for fuel tanks on the bridge deck under the cockpit seats directly ahead of each motor so the search begins for an off the shelf poly tank that will fit the space. I am curious as to what fuel capacity others are using for cats with this setup.

Steve.

 

[brian eiland]

For curiosity sakes, what are those twin 25 hp outboards going to cost you? (I'm not up to speed on current outboard cost).

Have you determined a 'likely' installation design at this point??

Have you posted, or do you have a layout plan of your vessel??

 

[Zulu40]

For curiosity sakes, what are those twin 25 hp outboards going to cost you? (I'm not up to speed on current outboard cost).

Have you determined a 'likely' installation design at this point??

Have you posted, or do you have a layout plan of your vessel??

Outboard cost? depends where you are, $5,000-$7,000 each, or around half an inboard install complete.

Depending on capacity (weight) as large tankage can weigh a lot. The tanks are best located on the CG of the vessel so trim is unaffected by the % capacity. If thats not ideal then as close to as possible.

 

[brian eiland]

I'd like to thank all for the their contributions. When I started this thread we had just gone to look at a Simpson 13m that was for sale in Florida. My son and his girlfriend have since bought it and we will be repowering it with a pair of Yamaha 25 HTs hence the thread. The boat is a bit of a project and we need to move it north to Duluth which is about as far west as you can get in the great lakes. The boat originally had saildrives but they were removed for unknown reasons and there are currently 2 Kubota diesels, 1 new the other rebuilt , 1 new sail drive leg, the other Mia.The engines are complete industrial units with no marinization parts and are up in the saloon. Having a preference for outboards anyway all this stuff will be sold and we will go the outboard route. We are going to have to come up with a very simple mounting system as we will be going down to the boat in a couple of weeks to prepare it for the winter but mainly to take lots of measurements and do sketches so we can fabricate the brackets at home before we do a 3 week work trip over Xmas where we will need to have a workable system by the time we head home, the goal being to launch in may and head north on the icw, so, how we mount the motors now needs to be simple, something we can install in a few days, it will not be the final solution but will still need to function well as its a lot of motoring between Florida and Minnesota. We do have 2 workable solutions figured out, the biggest problem is that Yamaha does not offer an extra long shaft on the 25 in the US…very dissapointing. Anyway, exciting times.

Steve

I did see this in reading back thru the subject thread.

So you may hook up a temp system, then plan a more permanent one after you get the boat back north??

 

[Zulu40]

you can get leg extensions for outboards too, 5" - 10"

just an example Im not recommending or affiliated with:

http://www.lathammarine.com/acc7.htm

 

[brian eiland]

Duo-prop, dual prop outboards

Has anyone on this forum had any experience with these somewhat rare outboards that make use of dual counter-rotating props. Seems they got pretty got reviews on this discussion,
http://www.thehulltruth.com/boating-forum/230846-duo-prop-outboard.html

https://www.youtube.com/watch?v=chfDSJ2d_a4

And I seem to remember seeing a VERY good video presentation of a duo-prop runabout challenge against an identical vessel with a single prop. I remember it took place in Venice Italy. And it may have been an IO type unit,...perhaps Volvo. But overall it really displayed the significant advantages of the dual prop arrangement.

Wish I could find that video??

 

[jorgepease]

The Yamaha TRP's are common in Texas where micro drafting boats jack motors high. They give great grip but it comes at a high cost and if they break expect a high repair bill.

The smallest motor I've ever heard they make them for was the 150. These days most, including me, use cupped props. They hold where other props just spin and create foam. The difference is night and day and it only costs like $60 to get a prop cupped. Baumann Marine is one of the best. One thing to consider is that it does eat up rpm's, reduce pitch is necessary.

Has anyone on this forum had any experience with these somewhat rare outboards that make use of dual counter-rotating props. Seems they got pretty got reviews on this discussion,
http://www.thehulltruth.com/boating-forum/230846-duo-prop-outboard.html

https://www.youtube.com/watch?v=chfDSJ2d_a4

And I seem to remember seeing a VERY good video presentation of a duo-prop runabout challenge against an identical vessel with a single prop. I remember it took place in Venice Italy. And it may have been an IO type unit,...perhaps Volvo. But overall it really displayed the significant advantages of the dual prop arrangement.

Wish I could find that video??

 

[brian eiland]

I cupped the prop on my 9.9 Yamaha hi-thrust outboard, and gained effectively almost another half a knot (calm water) speed out of it,...on 37 foot Louisiane catamaran.

Now that I recall it was also possible to remove that portion of the handle from the outboard engine that had the throttle twist control (and shifting lever if I remember correctly). I mounted that portion of the handle in a vertical fashion on the rear cockpit bulkhead close to where the helmsman would be standing during docking maneuvers. Just had to get some longer cables to make the connection between the now remote handle control and the engine itself.

That was a pretty slick deal as I no longer had to reach down to the outboard engine itself to give it throttle, nor to shift it.

 

[brian eiland]

Of course you could always go back to a more primitive method of dual propulsion....