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Old 06-03-2006, 09:30   #1
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Preferred power for a cat?

This morning I had the chance to see three cats hauled out and on the hard. One cat looked like it had twin inboards, with the screws coming out of the bottom rear of each hull.
The second cat had some type of inboard/outboard motor where the motor was in a compartment at the stern of the boat, but in between the two hulls(access looked pretty good unless you are in bad weather).
The third had a 45 HP Honda sitting on the back.

Can y'all help me with the pros/cons of each and which one you prefer. Thanks.

Also, if the boat is powered with gas, not diesel, what is the availablitiy of gas vs diesel in some remote or small island locations.
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Old 06-03-2006, 11:14   #2
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cat engines

First let me say you definitely want two engines - it just makes life so much easier in the marinas.

I have a PDQ32 with twin outboard engines mounted in wells about a quarter of the way forward. They tilt up when not in use which is ideal for sailing. They are easy to live with and perform very well - certainly a good solution for smaller cats. Negatives are limited charging ability and they are a bit noisy at higher speeds.

I also own a Leopard 38 that has diesel inboards. It's nice to have the power and the diesels are reliable. With fixed props there is a fair bit of drag and the engines are not light so you pay a price under sail however short of switching to electric motors and a generator I think inboard diesels are the only reasonable option for bigger cats.
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Old 07-03-2006, 03:53   #3
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Big disadvantage of outboard power is the lack of electric power generation. The ability to reduce drag and provide access to the prop is their strength. However, a saildrive tied to an inboard engine and folding props is IMHO the best compromise.

Another option is a single inboard engine attached to a long outboard type leg (sillette) which is used by a lot of Prout cats
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Old 19-03-2006, 11:49   #4
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I think anything over 30ft you would want inboards, you are going to either have or will be installing alot of electrical thimgs and you need to recharge your batteries.
I had sail drives on my 40ft cat that got sunk they were ok, required alot of maintnce, the intakes kept getting closed with barnicals and such. I have a privilege 12m now stright shaft, most excellent. Lot less maintance and I can replace a shaft with no problem, not so a sail drive.
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Old 21-03-2006, 15:10   #5
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Powering a cat

I wholeheartedly agree that a cat should have two engines. Having said that, I also believe those should be inboard. On our previous 36 ft. cat, not only did the outboard engines present a problem in charging the batteries, but they often did not have the "oomph" necessary for conditions.

We now have twin 30 h.p. inboards, and the difference is unbelievable. We can power through headwinds that the outboards could never handle. The maneuverability is amazing. I would simply never go back.

We haven't had the problems with our sail drives that seagrub had, and the newer models make changing both sets of zincs a piece of cake.
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Old 21-03-2006, 16:18   #6
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I have a single outboard and even with a high out of water profile can still make headway against 40 kt wind.

Mind you it is a 27 hp diesel!
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Old 14-03-2008, 09:49   #7
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27hp Yanmar on a Sillette drive leg. The drive leg swivels thirty deg either side which helps manouvreing no end. Motor is good for charging, the leg swings clear for cleaning, de-roping, broken prop changing. Why not plastic/aluminium props if they don't stay in the water? Twin motor/prop is better, redundancy and manouvring but heavier too. Warm winds.
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Old 14-03-2008, 10:02   #8
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I have 2, 27hp yanmars with saildrives. Manuverability is great, redunancy is there, and with the sail drives I have no shaft/stuffing box problems.
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Old 14-03-2008, 10:12   #9
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Quote:
Originally Posted by seagrub View Post
I think anything over 30ft you would want inboards, you are going to either have or will be installing alot of electrical thimgs and you need to recharge your batteries.
I had sail drives on my 40ft cat that got sunk they were ok, required alot of maintnce, the intakes kept getting closed with barnicals and such. I have a privilege 12m now stright shaft, most excellent. Lot less maintance and I can replace a shaft with no problem, not so a sail drive.
Tom
I don't want to take the thread too far off topic, but I must ask some Saildrive questions, since I now have a couple Yanmar SD 20s.

1) What maintenance did your saildrives on the 40ft cat require?

2) I have thru-hull intakes for my Yanmar diesel engines, which are attached to the saildrive units. I saw some type of intakes on the saildrives during my survey, but they don't supply the engine. Do saildrives have intakes for cooling purposes or something?

3) Does anybody use a long tube and pump to suck the old gear oil out of their saildrives through the top fill hole, rather than the underwater drain hole?

4) Do you keep them in gear while sailing? I noticed quite a bit of racket in the engine room (normal gear noise, not something broken) when I kept them freewheeling on my last leg of the trip.
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