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Old 16-04-2012, 21:23   #16
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Can it get you off a lee shore in 50 knot winds 5-6 foot seas when your anchor is dragging? Think about how u want to use it and you'll have your answer. I guess is no it won't
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Old 16-04-2012, 21:30   #17
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Re: Engine size

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Originally Posted by bmartinsen View Post
I'm no expert but a google search of "volvo MD2" looks like it's a 15.6hp engine. If it's a MD2B it might be a 25hp. Either way it's an old engine and a lot less than I would want on a 40ft'er. Parts might be hard to get,etc.. The 25 hp model might be ok depending on where you plan on going and how well boat/crew sails.

There's no way he's talking about an outboard. In Florida there are at least some bridges that will not allow you to pass except under power, so not having an engine (or having a very inadequate one) could be quite limiting.
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Old 16-04-2012, 21:30   #18
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Re: Engine size

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Thanks Guess should have asked What would be recommended size?
IMHO the engine should be sized to allow required hull speed without having the throttle wide open. I would suggest that an engine of about 65 hp would be approprate.
This would allow for power when required withoud excessive fuel consumption and engine wear.
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Old 16-04-2012, 22:26   #19
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Re: Engine size

Kiwitrucker, if the owner didnt know the horsepower he may not know the model #. Check the engine data plate to make sure that it is not an MD2B, that would be adequate for that size boat. It is 25 HP which is on the low end of power for a 40 foot but should be OK. If it is in good shape, they are a great engine,but yes! parts are expensive. If the rest of the boat looks good to you, have an engine survey done to determine price adjustments or the need to just bail out of the deal.____2 cents worth._____Grant.
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Old 16-04-2012, 22:40   #20
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Re: Engine size

I think you need 200 hp so you can tow the Dallas Cowboys Cheerleading squad on slalom skis!!!!

First, the MD2 is a mid 20hp engine. Had one in my Westsail 32. The westsail had the displacement of a 40 footer and pushed us along quite well. It is an adequate engine for that displacement but barely. We're sailors and it worked fine for us while sipping diesel. We wanted an engine to get us in and out of the slip and power when there was no wind. It would give us an easy 5 knot cruise at about a 1/2 gallon an hour in light wind conditions. We were overpropped so don't know what the max speed would have been but could get 6 k if we wanted to push it. When we had to go in the opposite direction as a strong wind, we motor sailed at 20-30 degrees off the relative wind but that almost never happened.

The cruising world seems to be populated with powerboaters who have a sailboat. They turn on the engine when speed drops below 5 knots and expect to power into a hurricane. If that's your style of voyaging go with something huge in the engine department. Might be interesting waterskiing the Cowboy's cheerleaders. If you are going to rely on the engine to save your bacon from dumb maneuvers and want hullspeed cruise in light conditions, an engine in the 35-40hp should suffice. If you are a sailor, the MD2 should work just fine.

You didn't mention the displacement of the boat. If it's pushing past 30,000 lbs, you might add 10hp to the above reccomendations.
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Old 16-04-2012, 22:41   #21
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Re: Engine size

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Hi, I am looking at a 41' yacht and another engine is partly installed. It is a MD2 Volvo which I'm told is 7.5 hp. The suggestion has been made that this is to small. Comments please.
41' yacht. Would that be a sailboat? If this is the case, its length is almost meaningless. What's its displacement?

41' yacht. Would that be a powerboat? If this is the case, its length is completely meaningless. Is it a displacement or planing hull? And what's its displacement?

While the engine sounds incredibly small unless it's some sort of specialty vessel, there's no way to comment intelligently unless we know a bit more about the boat.
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Old 16-04-2012, 22:43   #22
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Re: Engine size

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You didn't mention the displacement of the boat. If it's pushing past 30,000 lbs, you might add 10hp to the above reccomendations.
Sorry about duplicating this. It seems that roverhi and I were typing at the same moment. Great minds.....
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Old 16-04-2012, 23:16   #23
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Re: Engine size

Displacement is 22500 lbs 1959 41' Rhodes Sloop
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Old 16-04-2012, 23:40   #24
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Re: Engine size

Wonder if there's a typo. I have a CT41 ketch, displacement 28,000 lbs, came with a Volvo Penta MD21A, 75 hp. Boat came standard with a 50 hp Perkins....the Volvo was considered an upgrade. Unfortunately, parts are hard to get for the MD21A, and we replaced it with a 75 hp Yanmar.......too much power, actually, and I wonder if I'm putting extra wear on the engine running at too low rpm However it's nice to have all that power when bashing into 25-30 knot headwinds.....which we have done.
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Old 16-04-2012, 23:59   #25
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Re: Engine size

At the risk of offending CT owners, they have a bow as wide as a barn door and need all the power they can get to go against a chop. In a flat calm sea the Rhodes 41 and the CT 41 can probably do similar speeds with the same horsepower, but in chop or actual rough conditions the narrow bow of the Rhodes need less power to keep moving. If the engine turns out to be an MD2B it will be fine and the Rhodes will still outsail the Ct on any point of sail._____OOPS, here come the attacks.____Grant.
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Old 17-04-2012, 00:02   #26
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Re: Engine size

The CT41 is a clipper bow.....hardly a barn door!
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Old 17-04-2012, 00:04   #27
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Re: Engine size

If I was buying a new diesel for your boat I would be looking at something like the 38 hp Volvo. Yanmar have a similar product at 39 hp but I'm not too sure Perkins make that size any more.
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Old 17-04-2012, 00:13   #28
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Re: Engine size

Here are the calculations for a displacement of 22,500 lbs.
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Old 17-04-2012, 07:58   #29
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Re: Engine size

General rule of thumb for a sailboat is that you want an absolute, bare minimum of 2 hp (at the shaft) for every ton of displacement. A better number is 3 hp for every ton of displacement. And most of the sailboats currently being sold carry about 4 hp per ton of displacement. Anything over about 6 hp per ton and you are just wasting horsepower.

So, with a displacement of about 11 tons you would want a diesel somewhere between 22 and 44 hp. Something up to 50-60 hp would not be excessive, but you really don't want to go over that.

Can you get by with less horsepower? Absolutely. You can get by with no engine at all, if you are a good sailor who plans carefully. But consider resale value. With an engine that doesn't measure up to the current standards for horsepower you are going to have trouble selling it, and will probably have to make serious concessions on the price. Were I buying an 11-ton sailboat today that only had a 10 or 15 hp engine in it, I would insist on a low enough price that I could afford a repower to a 35-40 hp engine.
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Old 17-04-2012, 08:37   #30
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Re: Engine size

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Originally Posted by kiwitrucker View Post
Displacement is 22500 lbs 1959 41' Rhodes Sloop
I would want at least 28 hp for that boat. A more ideal engine might be 38 hp.
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