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Old 07-08-2013, 14:12   #1
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Is a 9.9 Outboard Enough for a 38 Foot Boat?

I am looking at a 38 foot boat (displacement 17k before gear) without an engine. Great price, and rigging and sails look good. I would like to mount an outboard like I have on my current boat, but there is a 10k difference in displacement. Does anyone have any experience with this or any thoughts on the matter.

I use my engine now to maneuver in and out of the slip and that is about it. Thanks all for your time and replies.
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Old 07-08-2013, 14:28   #2
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Re: Is a 9.9 outboard enough for a 38 foot boat?

I think it will be dicey using it for maneurvering. It'll move the boat along well in a straight line. There are a lot of great deals out there in need of $15k engines.... be careful!
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Old 07-08-2013, 14:47   #3
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Re: Is a 9.9 outboard enough for a 38 foot boat?

The general rule of thumb is 1 HP per 500 lbs for displacement cruising. If you're only going in and out of a marina, you might get by with 9.9. If you need to run an inlet against the tide, or bash to windward, etc, you'll wish you had more.
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Old 07-08-2013, 15:14   #4
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Re: Is a 9.9 outboard enough for a 38 foot boat?

CAL 2-27 sailboat specifications and details on sailboatdata.com is the disp for my boat
6700
I have a 5ph.

According to the formula, I should have a 13 hp engine

I have about 30% of that and get to 5-6 knots depending on my bottoms cleanliness.

I would love to test the 9.9 on there without buying the boat, but there is no way to do so. Other than actual testing, I could not say. It would be a neat expirement

I know a lot of cats use small ob and it is more socially acceptable than doing the same on a mono.
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Old 07-08-2013, 15:22   #5
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IMHO go with the same HP as the original engine. Assuming the boat is from a reputable builder, the designer already determined the smallest engine that would reasonably power the boat.

It is theoretically possible to move a 17,000 boat with a 5hp engine. But when docking and you need to reverse NOW, will it have the power to stop the boat? When you must use the iron Jenny to make port in a storm, will it have the power? I would gladly wager on the "No" side of both those questions.
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Old 07-08-2013, 15:25   #6
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Re: Is a 9.9 outboard enough for a 38 foot boat?

Snore, No doubt I would not use a 5hp on a 17k disp boat. My boat is half that and my engine is half the 9.9. I would not try it, but would use it is I had a chance to test first and determine if I would feel comfortable. I wish I knew someone with that setup so I could see the downsides personally. I like rules of thumb, but love actual testing so much more. I just dont want to test on my dime;-)
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Old 07-08-2013, 15:59   #7
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Re: Is a 9.9 outboard enough for a 38 foot boat?

on flat water with a high thrust propellor it will just about work,plumbed in engine controls etc.

any stronger conditions and the weight and windage of a 17k lump vs 10hp will result in cavitation and loss of control,though with wind if you are quick getting the sails up,,,,,,,

best to look at getting the main engine replaced if serious cruising is your aim
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Old 07-08-2013, 16:11   #8
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Re: Is a 9.9 outboard enough for a 38 foot boat?

Quote:
Originally Posted by Snore View Post
IMHO go with the same HP as the original engine.
However, inboard HP is not the HP at the prop. Whereas, outboard HP specs...are at the prop. So, technically, you could get away with a smaller outboard with almost equal results.
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Old 07-08-2013, 16:52   #9
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Re: Is a 9.9 outboard enough for a 38 foot boat?

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However, inboard HP is not the HP at the prop. Whereas, outboard HP specs...are at the prop. So, technically, you could get away with a smaller outboard with almost equal results.
hmm my 62 HP inboard would = something pretty massive hanging off the arse end.
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Old 07-08-2013, 17:51   #10
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Re: Is a 9.9 outboard enough for a 38 foot boat?

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hmm my 62 HP inboard would = something pretty massive hanging off the arse end.
Nah..only about 214-220 lbs dry weight

Good rule of thumb is outboard can be 10% smaller than inboard (HP)
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Old 07-08-2013, 17:58   #11
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Re: Is a 9.9 outboard enough for a 38 foot boat?

At high tide with no wind I towed a 13 ton double ended sailboat about a mile using a hard dink with a 2 1/2 hp motor. I emphasize the no current and no wind.

When working the boat uses a 37 hp 3 cylinder Volvo diesel that had a bad transmission and I wanted to move to another slip. As usual my boat mechanic and I have different ideas on what fixing in a timely manner means and I even pulled the transmission for him.
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Old 07-08-2013, 17:59   #12
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Re: Is a 9.9 outboard enough for a 38 foot boat?

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Nah..only about 214-220 lbs dry weight

Good rule of thumb is outboard can be 10% smaller than inboard (HP)
problem with outboards is the lenth of the drive leg even a long shaft is only 25 inches below the surface,with the motor getting inundated in any sea conditions on a yacht unless it is fitted in a purpose built well
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Old 07-08-2013, 18:01   #13
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Re: Is a 9.9 outboard enough for a 38 foot boat?

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problem with outboards is the lenth of the drive leg even a long shaft is only 25 inches below the surface,with the motor getting inundated in any sea conditions on a yacht unless it is fitted in a purpose built well
So true..it has limitations...pro's and con's..which have been deliberated here many times. It's all up to the individual on whats more important...the conditions they expect to be in...etc...etc.
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Old 07-08-2013, 21:50   #14
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Re: Is a 9.9 outboard enough for a 38 foot boat?

While I agree in a calm situation you could get the boat going at a decent clip. I believe the lengthy amount of time it takes for you to reach top speed is indicative of the kind of times your going to need to come to a stop. I have a similar sized boat though a couple tons heavier and I found myself in the situation where I misjudged an approach to dock when getting used to the boat and I appreciated having the 40hp perkins and large prop. Of course the more familiar I become with this boat the less I will need that. But as they say I would rather have it and not need it than... you know the rest. Then again, I have heard tale of people who have done multiple circumnavigations without an engine.

Good luck with the boat!
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Old 07-08-2013, 22:01   #15
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Re: Is a 9.9 outboard enough for a 38 foot boat?

36' 12 ton boat, I have a 52 HP.
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