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Old 10-03-2014, 08:08   #31
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Re: 40 Horse Outboard on Catalina 30?

[QUOTE=SkiprJohn;1488057]
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Originally Posted by valhalla360 View Post

Bristol 27 LWL is about 20 feet. Hull speed is 6. He's doing great from 4-6.
I actually bought the engine just to get me out of the slip (and/or the creek) since my first 15 years of sailing was on boats without engines.

I bought the boat on the Eastern Shore of Virginia at a marina "up the creek" about 3 miles. The channel was very narrow and you couldn't tack to sail out if the wind was wrong. You could also only come and go during high tide. The boats at the marina drawing 4' or more sit in marsh mud within 2 hours either side of high tide which makes it nice and stable during low tide!

But after having the boat for a couple years so much for engine-less cruising. I've found that running the engine when the wind is light with the sails up can add 2-3 knots which is really nice when you are trying to get across the bay to your anchorage spot to catch fish for dinner.

But I still wouldn't put a larger outboard on this boat. On a Catalina 30, I'd probably run a 9.9 or 15 hp or find another old diesel like another guy said. I'm thinking the Catalina has a lot of freeboard on the stern making it hard to do the outboard thing.

With my 25" shaft, I have the engine up all the way on the bracket setting during docking maneuvers. The power head is actually above the deck on my Bristol 27 in that position so it's easy to steer, but the engine is still low enough for the impeller to pump water. It's actually the same level as an outboard on a power boat would be planed out in this position.
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Old 10-03-2014, 13:14   #32
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Re: 40 Horse Outboard on Catalina 30?

[QUOTE=valhalla360;1488508]
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Originally Posted by SkiprJohn View Post

Fair enough but as I said, it's no a linear relationship between HP and length, so cutting 1/3 off the waterline length doesn't mean a direct 1/3 off the HP requirement.

Also, what is the LWL when at hull speed? I'm not familar with the particular quirks of this design but a lot of mono's used to have overhangs that at dock resulted in a short LWL but once you got them moving, the effective LWL got longer. This is something that is not as common or at least far less pronounced in cats.
You're making some good points. My experience with engines is that trying to push for a hypothetical hull speed is very costly in fuel and in extra cost for a more powerful engine. In the Catalina 30 a Honda 7.5 4 stroke would be about the right weight and power with a great deal of economy in purchase and fuel.
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Old 10-03-2014, 14:23   #33
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Re: 40 Horse Outboard on Catalina 30?

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Originally Posted by valhalla360 View Post

You're making some good points. My experience with engines is that trying to push for a hypothetical hull speed is very costly in fuel and in extra cost for a more powerful engine. In the Catalina 30 a Honda 7.5 4 stroke would be about the right weight and power with a great deal of economy in purchase and fuel.
After comparing fuel efficency with our 25hp 4stroke EFI vs similar boats with 9.9 or 15hp 4 stroke on Gemini's, there appears to be negligible fuel efficency differences...except for the fact that it's easier to push the throttle lever forward a bit more and make speed which comes at a cost to fuel efficency.

As long as we back it off to say 5kts, the fuel usage is about the same. Given the size of the boat, the extra weight difference isn't a big deal for cruisers (racers might feel differently).

The reason for suggesting 25hp is not for calm conditions easy situations but for situation where the extra power comes in handy. We have a mount that will take our 5hp dingy motor and it will push the big boat 3-4kts in dead calm conditions but I don't think it would do much against any kind of head wind and around a dock, there is no chance if you make a mistake.
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Old 10-03-2014, 14:41   #34
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Re: 40 Horse Outboard on Catalina 30?

I would just like to mention that if you are mounting an outboard of that HP on a lifting bracket make sure it is rated for the size of engine you plan on using.
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