4hp on a small yacht

[Vern]

My Kestrel 22ft sailing tug, has the standard 7hp Vire two stroke fitted but not working presently (maybe possible without too much effort to get working) and a 2008 Mercury 4hp two stroke.

Last Monday week, Kathy and I came back into Weymouth at 1.35pm having gone out for a lunchtime 'sail' at 12.
It seemed the outboard was getting us nowhere, the bridge opens at 2pm so unless we stayed out longer until 4pm, I had to get the boat home.

I can't really judge how far out we were, but it was a tad further than where several other yachts were 'ticking over', getting their sails down - maybe half a mile to the harbour entrance?

The progress was very very slow, I thought we wouldn't make it, but looking across to Portland, I could see the gap closing up, obviously we were going forward!

We made it, so fine and dandy.

But would the 7hp original have made it easier by much, or should I look at putting a bigger engine on the stern?
Not interested in zooming here and there, but I do want to get home, I should add the sails were not up, so the outboard was doing all the work.

And the keel is like an underwater takeaway for fish, it needs cleaning.

 

[MissIsle]

I have a 22' Venturer which is pretty similar to you.
We have a 10hp inboard & it struggles against the tide sometimes, particularly in the estury's. I think the 4hp outboard would be better off on the tender & you should look to go up to at least 7hp.

 

[VicS]

Drty bottom may well be your problem.

But for me a 4hp would be too small on a 22 footer. Not a light one either I'd go for an 8HP

I have 6hp on 19ft. but 4 hp with a high thrust prop might be enough ... just.

 

[Giblets]

Drty bottom may well be your problem.

But for me a 4hp would be too small on a 22 footer. Not a light one either I'd go for an 8HP

I have 6hp on 19ft. but 4 hp with a high thrust prop might be enough ... just.

Vic, interested to hear that you have a 6hp on a 19 footer. How does that perform? I have just bought a 6hp Tohatsu Sail Pro outboard for my Leisure 17 which I hope will push her along when needed without over working the engine. Most other L17 owners seem to have opted for a 4hp unit.

 

[Vern]

Many thanks to you both.

Had considered the 7 and 4 combined....but maybe a 10hp outboard would be better.
(allowing for a 1970's worn two stroke)

 

[Seajet]

Vern,

remember the snag with an outboard is the prop coming out of the water in any waves, plus unless you have remote controls to the outboard ( ? ) it means dangling over the stern facing backwards just at critical moments like marina berthing - tip people off and you'd be able to sell tickets and popcorn !

My boat was happy with a 4hp outboard in the well, went across the Channel with it in calms several times, now have a 5 which is plenty.

Your boat will be a bit draggier being twin keel, but I think the weedy bottom is the real killer; also have you got a fixed blade - rather than folding - prop on the defunct inboard ?

That, and a weedy bottom, is asking a lot.

An outboard on the back is a pain, weight in the worst place too, I'd have a good go at getting the inboard going.

In the meantime lets get you using sail power, and try a long handled stiff brush to get what weed you can off.

 

[VicS]

Vic, interested to hear that you have a 6hp on a 19 footer. How does that perform? I have just bought a 6hp Tohatsu Sail Pro outboard for my Leisure 17 which I hope will push her along when needed without over working the engine. Most other L17 owners seem to have opted for a 4hp unit.

Plenty big enough.

The first engine was a 5hp volvo penta. I guess if you measured its power output by the current Icomia 28/83 standard it would be 4.5 hp at the most. In all honesty that was powerful enough. I changed really because I wanted a long shaft engine and a more reliable one!

Choice of prop is an important factor. Standard props are suitable for fast light runabouts. For a slow displacement hull you need a smaller pitch and perhaps a larger blade area.

 

[oldharry]

4hp is adequate up to about 20 ft, but anything bigger really needs a bit more. When I first started sailing the old Seagull century which was vaguely described by the maker as '3-4hp' was more or less standard auxiliary standard power for anything small enough to be outboard powered. Mind you, the massive 5 bladed prop on the later ones gave a lot more thrust than the smaller higher revving props of modern japanese engines.

When money perimitted one upgraded from the old Century, or Silver Century (4-5hp - such power!) to a Stuart Turner P5 4 hp inboard, which powered many yachts up to around 25 feet. Above that, one graduated to the P55 - all of 8 hp in a twin cylinder version. Towards the end they uprated it to 10hp. They all shared the primary Seagull characteristics: if you had a good one, it was a gem of a motor, totally reliable as long as you kept half a dozen spark plugs aboard. If you had a bad one, you spent half your sailing time tinkering with the darned thing trying to get it to go at all!

The Vire 6 that you have was a huge improvement, and a number of older boats still use them quite happily. Simple basic engines with a few idiosyncracies which you need to be aware of, and if it is not worn/rusted out, a far better bet than hanging an outboard on the back! Spares are not cheap, I am told!

 

[Vern]

4hp is adequate up to about 20 ft, but anything bigger really needs a bit more. When I first started sailing the old Seagull century which was vaguely described by the maker as '3-4hp' was more or less standard auxiliary standard power for anything small enough to be outboard powered. Mind you, the massive 5 bladed prop on the later ones gave a lot more thrust than the smaller higher revving props of modern japanese engines.

When money perimitted one upgraded from the old Century, or Silver Century (4-5hp - such power!) to a Stuart Turner P5 4 hp inboard, which powered many yachts up to around 25 feet. Above that, one graduated to the P55 - all of 8 hp in a twin cylinder version. Towards the end they uprated it to 10hp. They all shared the primary Seagull characteristics: if you had a good one, it was a gem of a motor, totally reliable as long as you kept half a dozen spark plugs aboard. If you had a bad one, you spent half your sailing time tinkering with the darned thing trying to get it to go at all!

The Vire 6 that you have was a huge improvement, and a number of older boats still use them quite happily. Simple basic engines with a few idiosyncracies which you need to be aware of, and if it is not worn/rusted out, a far better bet than hanging an outboard on the back! Spares are not cheap, I am told!

Thanks for that, I have noticed how the prop leaves the water frequently when at sea and also when someone is on the bow.
Think I need to see how easy it could be to get the Vire working - impellor apparently is the issue.

 

[Evadne]

Another vote for the weed, you shouldn't underestimate the speed it will take off you. My 3.5 ton long keeler has a 6.5hp inboard - the old Yanmar 1GM7 which is fine for 4 knots or so in calm waters until the bottom gets really weedy at the end of a long, quiet season especially. In Septembers past we have more than once ended up plugging the tide into Portsmouth harbour at 0.01 knots over the ground!

 

[snowleopard]

I had several Sonatas which were powered quite adequately by Mariner 5HP motors. One got nicked so I replaced it by a Yamaha 4HP and It went just as well. The Sonata is 23 ft and 1.1 tonnes displacement.

 

[Achillesheel]

My Achilles 24 has a Mercury 4hp in a well which will get us up to 4kts or thereabouts. We have also used a 2.5hp (which we have for the dinghy) in emergency to get us into a marina, or to a mooring when the main engine fails.

 

[Sybarite]

My Kestrel 22ft sailing tug, has the standard 7hp Vire two stroke fitted but not working presently (maybe possible without too much effort to get working) and a 2008 Mercury 4hp two stroke.

Last Monday week, Kathy and I came back into Weymouth at 1.35pm having gone out for a lunchtime 'sail' at 12.
It seemed the outboard was getting us nowhere, the bridge opens at 2pm so unless we stayed out longer until 4pm, I had to get the boat home.

I can't really judge how far out we were, but it was a tad further than where several other yachts were 'ticking over', getting their sails down - maybe half a mile to the harbour entrance?

The progress was very very slow, I thought we wouldn't make it, but looking across to Portland, I could see the gap closing up, obviously we were going forward!

We made it, so fine and dandy.

But would the 7hp original have made it easier by much, or should I look at putting a bigger engine on the stern?
Not interested in zooming here and there, but I do want to get home, I should add the sails were not up, so the outboard was doing all the work.

And the keel is like an underwater takeaway for fish, it needs cleaning.

Two main problems for you :

the dirty bottom
Adverse conditions. In calm windless water your 4hp will bring you up to hull speed but in any stiff wind or tide against or large waves you won't get anywhere with it.

The ideal for you would be say a small diesel but expensive. I would try at least to get your Vire working again.

 

[Horace]

I own a Kestrel 22 & a more stable boat for the size I can't imagine so if the outboard comes out the water with you standing on the bow then I suspect that your outboard is a short shaft or you are too fat
I did away with the Vire because it caused me endless trouble & bought a decent 10hp long shaft sail drive outboard.Now I have additional storage space plus the piece of mind of having less sea cocks & old shafts offering resistance.Plus I have a lovely sweet smelling boat.What more could you want!
It also provides all the electricity I need.

 

[TSB240]

We use either a 4hp or 6 hp two stroke to power our TS240.

It has a well so no need for long shaft.

When clean the 4hp can match the 6hp and we see 5.5 to 6 knots max speed through the water in calm conditions

Any weed or head wind/ chop the 4hp struggles but has got me home.

Boat is 24foot and weighs in at over 1.5 tonnes.

Fitted a high thrust prop to the 6 hp and this delivers loads of thrust especially when manouvering at slow speeds. I reckon this is better than my old 8hp with a standard prop.

 

[fisherZ]

Vern.....it's easy enough to use the grid to clean your bottom.
You had the tail end of a spring tide against you on the 4th July, so that probably cut your claggy bottomed speed by half.

 

[Vern]

Vern.....it's easy enough to use the grid to clean your bottom.
You had the tail end of a spring tide against you on the 4th July, so that probably cut your claggy bottomed speed by half.

Thanks I thought it was trickier than usual.
Some useful knowledge coming through on the thread, thank you it's much appreciated from you all.

Young Seajet and I will be giving the old Vire a tickle to see if we can wake it up over the weekend!
And maybe a scrub on it's arse to boot.

 

[PeterR]

I had several Sonatas which were powered quite adequately by Mariner 5HP motors. One got nicked so I replaced it by a Yamaha 4HP and It went just as well. The Sonata is 23 ft and 1.1 tonnes displacement.

I also had a Sonata with 4Hp engine which was absolutely fine. Motored back from the continent several times in calm weather. You do need to have the correct large blade fine pitch prop, Using the standard prop meant for a planing boat does not work.