Is my outboard too big for my yacht?

seanfoster

seanfoster

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First of all, It's been over 5 years since I've been on this forum (ever since I had to sell my 28ft yacht /forums/images/graemlins/frown.gif ) but I'm back on the water this season with a much smaller version, but who cares!

Anyway I have a 15hp evinrude outboard which I use on my Zodiac, it's quite lightweight, my new yacht is a 19ft trailer sailer and although I know the outboard will fit onto the transom without any problems I'm just wondereing if there's any problems using it on it?

I understand that I will only ever be able to reach the max hull speed with the outboard (and I don't intend to open it up to full power anyway) but just wondered if there was any problems I should be aware of using an overpowered motor?

Can anyone help?
 
G'day seanf and welcome back,

We had a bloke here who ran a 25HP outboard on a 21 footer, never had a problem, but always beat us back to the bar on a calm afternoon.

You might like to check your mounting on the boat and consider some sort of rev limiter. Other that I can't a major problem.

Avagoodweekend......
 
Weight that far aft may be an issue. If the engine is much too heavy the boat will squat a bit. Otherwise - would n't have thought it would be a problem if you do n't open the engine right up. Even then you would probably just create a hole around the prop and go even slower!
 
No problem with power, only the weight; you will be able to go against the tide easy enough!. Better to be overpowered than underpowered.
 
As long as the bracket is strong enough you shouldn't have problems. My 10 hp twists the bracket quite a lot, but hasn't broken it, yet.
 
If its used on a zodiac it probably has a standard drive leg. Unless its fitted in a well (that would be a big hole for a 15HP) then you might find you lift the prop clear every time you go up and down a wave.
 
Can't quite get my head around a 15hp engine on a Zodiac! I have a vision of a 3 person floppy. I'm hoping you mean a small RIB.

Just to buck the trend of the advice offered so far, I wouldn't put a 15 on a 19ft trailer sailer. What is the boat manufacturers maximum rated engine, around 4-5 bhp? It's too big and would compromise the vessel IMHO.

Get it on e-bay and buy and nice new 4 stroke 5 hp with the proceeds!
 
A couple of boats ago we had a 22ft yacht (Newbridge Venturer) that came with a 14hp Suzuki engine when we bought it. Didn't have any problems with the setup at all except the engine was unreliable. Changed it for a Tohatsu 5hp and enjoyed much more sedate motoring. If the engine fits in a well check and double check dimensions before thinking of getting a different engine.
 
I assume the existing outboard is a 2 stroke. If so any replacement is likely to be a 4 stroke, which means that you will have to have a significant power reduction to see much weight reduction.

Therefore the biggest problem is too much power for the transom fitting. you may say you wont use it, but one day when trying to beat the tide . . . . .

The next biggest problem if it is a short shaft is cavitation and lifting out of the water when trying to make progress against the waves. A long shaft will assist here.

Personally I would be trying to find a 2 stroke tohatsu 9.8 hp long shaft as I reckon that would be a better compromise.
 
So long as the bracket and transom fixings are strong enough it should be fine.

I would be carefull if you turn the engine as well as the rudder. If you gave a burst of full power accidentally while the engine was turned it would put a big twisting strain on the bracket/transom .

Its not ideal for performance under sail you dont want extra weight on the back but for cruising it would be ok.
 
Might seem a little OTT, but seems okay. That said and a point for other forum members to consider is this. (not sure on other major races) On the Round the Island Race in the instructions it states that your outboard must be taken off/contained within the boat. 4-5hp motors are easy to take off at sea, 9-10hp less so, 15-25hp very hard going to take off at sea. If you don't take the engine off then you face disqualification. Worthwhile thinking about if you race regularly.
Why does the ISC have this rule, well having done RIB support for many years in this race, if someone tacks in front of you and you then hit their outboard (Being out of the water in the horizontal position) it cuts into your hull, lodges in place, then as the two boats break away the propellor having turned slightly during the collision the prop will now be lodged in the other boats hull, thus as the boats come apart and both boats sails come under full load the outboad gets ripped off it's mounting then gravity takes over and the engine falls to the bottom of the sea having taken a considerable chunk out of both boats hulls...
If you are racing under such circumstances by a 5hp, as people who race for 16hrs round the Island don't see the funny side when they get in to find a DSQ notice...Hope this helps you and others
 
Seems sensible with such a lot of boats in a confined space. Bit of a pain if the outboard is bolted to the bracket and has remote controls and powercables attatched though. Do they also insist on no anchors on bow rollers?
 
I used to have a 15hp Evinrude on an open 15' fishing dinghy. I seem to remember that it was the same engine as the 10 and the 7.5, with the two less powerful engines being de-rated. It might be worth finding out what it weighs, compared to a modern 5-7hp 4 stroke - there's probably not a lot of difference. When it's running, of course, it's not the dead weight but the thrust that will be the determining factor, bearing in mind that it is attached to a bracket rather than fixed direct to the transom. Most brackets are a bit floppy and will move when you put the engine in gear - even my 3.5 Tohatsu seems to make mine wobble about a bit.
Goldens14's point about taking the engine off is very valid - even on a mooring it requires a combination of grunt and gymnastics that could end up with the top spot on 'You've been Framed'.
 
I am intrigued and surprised by the racing rules for RTI.

By contrast the Victorian TS association who run a race every year on the Gippsland Lakes (approx 900 starters) (last weekend as it happens) specifically require all yachts to have a o/b motor in place and functional. I presume for self rescue.

I reckon the rules for RTI are more related to cheating with motor.
Sure an O/b can do some harm but is more likely to fall off than damage another boat and the safety aspects of being able to get out of the way of shipping or danger would seem to be much more important to me. For all that I always race without motor. (leave it at home) olewill
 
If its a 2st you may have problems with it oiling up, they hate running for extended periods under light loads. Carrying that much petrol on board is also a safety issue. Are you still going to be using it on the Zodiac and thinking one engine for both jobs? Its a lot of wt to transfer without a hoist. A long shaft 4st 6hp with fine pitch prop is what you want.
 
Macgregor 26s go pretty well with a 60 horse and no water ballast - you can even use one to water ski with.

Main thing to remember when using a larger engine is to fit an anti-cavitation plate above the prop.

Otherwise the sky's the limit though twin 200s would probably be over-egging it a bit.
 
[ QUOTE ]
...Do they also insist on no anchors on bow rollers?

[/ QUOTE ]
Yes they do.

As an aside, Cowes harbour Byelaw 5 also says that anchors should be stowed inside the rail on "any vessel laying alongside or near any Quay within the Harbour". But not many people know that...
 
My 21' yacht was rammed up the a**e by a much larger yacht on the finishing line of last year's RTI. It wasn't our fault of course /forums/images/graemlins/blush.gif but I was extremely glad that he didn't have his anchor on the bow roller. As it was some easily repaired damage was done to my pushpit, which was partially torn free from its through-deck mountings, but if the other guy had had an anchor on the bow roller, odds are that it would have caught on the pushpit and torn it clean off.
 
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