is 20hp enough for a 35' fin keel yacht ?

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is 20hp enough for a 35\' fin keel yacht ?

I am looking at a 35 foot fin keel yacht, 27' LWL, beam 10'10", draft 5'6" displacement 4.8 tonnes or 10,500lbs. (Trapper 700)
She has a new Beta BD722 engine with a "claimed" cruising speed of 5kts.
Seems a little underpowered to me.
A lot of boats I've looked at 28-32' have the Beta 28hp nowadays so I'm a bit concerned.
A decent engine matters to me as I want the option of plugging into a head wind and sea to get home.
What does the panel think.
Should I walk away or is there any way of getting more power.
Would a Brunton self feathering prop make much difference ?
Thanks in advance.
 
Re: is 20hp enough for a 35\' fin keel yacht ?

Depends how much power you want. 4 hp/ton is pretty reasonable as an auxiliary. If you want to operate as a motor sailer then the larger engine may be a good idea.
 
Re: is 20hp enough for a 35\' fin keel yacht ?

Well, I can tell you that 15 hp is not enough for a 37ft 10 ton displacement long keeled yot, cos that's wot I've got, and we achieve the dizzying speed of 3.5 knots flat out in a clock calm.
 
Re: is 20hp enough for a 35\' fin keel yacht ?

I've got an 18hp Yanmar with a 2 bladed folding prop on my 34 foot boat. There are times when I'd like a bit more getting out of tight berths, but it otherwise drives the boat just fine. We can do 6.5 knots on smooth water and with no smoke. I've just come back from a charter on a Jeanneau SO 34 with a Yanmar 3GM30 with a 3 bladed prop. There was a massive difference in performance under power, but then again, there was also a massive difference in performance under sail. I suppose the only way to find out is to take the boat out for a test drive.
 
Re: is 20hp enough for a 35\' fin keel yacht ?

The best advice I got when buying our 1st yacht was you can never have too much power.

Having said that I notice that all modern boats have much more powerful engines than their equivalents of a few years ago.

The question is does it matter to you. I would suggest that providing you can tolerate the slower speed when no wind and the yacht has the capability to beat off a lee shore you may be happy. A purist may only use the engine when berthing while a large number of sailers use the Iron Sail as soon as their speed falls below say 4 or 5kts.

All boats are a compromise so you inevitably have to decide what is most important for you. Good Luck
 
Re: is 20hp enough for a 35\' fin keel yacht ?

It seems borderline to me, but I'm a raggie who has switched to power! Your hull speed is a little over 7 knots and I've always felt the engine should be able to achieve hull speed in smooth water. Ron Holland reckons 5 hp per ton is right, and that is what many production yards fit. My last two cruising yachts had 5hp per ton and I never thought they were overpowered. To maximize the drive capability of your engine you need a large diameter high pitch propellor which will be a liability when you sail. A feathering or folding prop will help with sailing, not with motoring.
 
Re: is 20hp enough for a 35\' fin keel yacht ?

I think Trapper 700s originally had Volvo MD11C 23HP motors so the replacement has been rounded down in size and not up. 5kts is a bit slow for cruising on this size, 6kts should be a target IMO, maybe there is a prop size issue as well. I think it might be a saildrive?

BTW standard Trapper 700s were usually fitted with outside cast iron keel with a raisable metal centreboard contained in it, although I know of one that was a fixed fin and was in charter in the Caribbean.

Robin
 
Re: is 20hp enough for a 35\' fin keel yacht ?

Arguably, it's at the low end of the scale but perfectly adequate. The fact that it's a new engine must count in its favour.

If the rest of the boat is what you are looking for I certainly wouldn't "walk away from it" simply because of the engine size.
 
Re: is 20hp enough for a 35\' fin keel yacht ?

My 2 penny'th, FWIW:

Hull speed for your boat should be almost 7kts and to my mind any boat that can't hit hull speed in smooth water is under powered. 5kts flat out means around 4kts cruising.

Where you'll have problems is punching a chop or when you need a bit extra to fight your way in or out of somewhere against the tide. With my old engine I once took 3/4 hour going from No4 to Ballast - maybe 600yards! Last Sunday I reckon there was close to 4 1/2 kts of ebb tide as I was going into Portsmouth harbour and a nasty confused sea from all the wash that made the sails useless in the light wind. Frankly, I doubt the Trapper would have have made it.

Imagine yourself running a bit late to get somewhere a tad shallow, dead calm and an ebbing tide to punch. The engine's flat out and the GPS says 4kts. In an hour you'll just have enough water to get in, but the GPS also says 4.5 miles to go...

Now imagine the same scenario with a relaxed engine and 5.5kts on the GPS.

I reckon 30-35HP would be nearer the mark. The bigger prop that would go with the bigger engine would mean a small loss of speed under sail, but a feathering/folding prop on the bigger engine would probably give you better sailing performance than with a smaller, fixed prop.

(All strictly IMHO, and with no claims to expertise /forums/images/graemlins/smile.gif)
 
Re: is 20hp enough for a 35\' fin keel yacht ?

I have a Yanmar 2GM20 in a five ton boat and it's definitely not powerful
enough, but I've put up with it for many years. Motoring speed is rarely over
4 kts, occasionally 5kts in a flat calm on full throtle. Since a 3cyl 27HP is a tad
expensive I'm considering a 3.2/1 gearbox instead which would allow a larger
prop to punch into headwinds,seas although possibly at the expense of calm
motoring speed. My family actually complain about the slow motoring in the Med
although not about sailing speeds.
 
Re: is 20hp enough for a 35\' fin keel yacht ?

As a Dutch gentlemen some years ago, informed me. In Holland we have 1hp for each foot, why you English have such little engines we do not know! and that was with a 15hp on a 26'.... I suspect he was about right.
 
Re: is 20hp enough for a 35\' fin keel yacht ?

Volvo MD7B - 17hp - 5.8knots. Range 500miles on 1 litre per hour.

SJ36. lwl 28ft. 4.5tons.

Sails rather faster.Range rather greater.
 
Re: is 20hp enough for a 35\' fin keel yacht ?

I have an Evasion 32 with a 47SHP Perkins 4108. It does 3.5 knots at 750 rpm.. 4 knots at 1000 rpm, 5 knots at 1500 rpm and 6 knots at 1800 rpm. It does 7.7 knots at 3500 rpm, becomes pig to steer and tries to plane! The 27 year old engine works fine, but is grossly overpowered. She weighs close on 6 tonnes, and so it may be that the power should be related not only to size of boat, and hence wetted area, but also the amount of weight that has to be pushed thro the water. Suck it and see, but I would be very unhappy with a 35 footer which can do only 5 knots, because Pompey harbour has a 5 knot flood tide during springs, and there are times that I have to punch though it
 
Re: is 20hp enough for a 35\' fin keel yacht ?

I have a 33' which weighs 8000lbs and has a 21hp Albin....

Its a little underpowered, and at the weekend in a short choppy sea was working hard to make headway of about 3.5kts over the water..... I can however make 5.5kts in a flat sea at a sensible rev point.....

IMHO your prospective purchase is also a little underpowered...... but not dangerously so....
 
Re: is 20hp enough for a 35\' fin keel yacht ?

I put in a Beta 18hp into a 29ft westerly 4 years ago and there was bags of power in reserve - extremely good responsive engine.
 
Re: is 20hp enough for a 35\' fin keel yacht ?

Thanks for all the posts so far.
I will be looking over the boat later this week.
If I buy, will of course wait and see how we get on.

Worst case is upgrading the engine surely the cost difference shouldn't cost much more than a new Brunton prop ? What should I expect for a new hardly used Beta 20hp ?!

I definitely need the power as the ebb on the Ore can easily run up to 4 kts in the entrance.
The replies so far have just confirmed my original thoughts..
 
Re: is 20hp enough for a 35\' fin keel yacht ?

I wasn't going to add anything to the wise words already spoken until I read your last comment about regularly needing to head a 4kt tide.

I agree with the 5hp per ton rule. My 35ft boat is 5tons and with 27hp feels great. In flat water her clean sections allow me to motor at 7.8kts. But as soon as the widn and chop come up this drops back. I can usually maintain 5kts even into the worst stuff but if I was plugging a 4kt tide I would not have much extra margin in hand.

I would have said your current spec is at the low end of the range but still just acceptable. But in the light of regulalr 4kt foul tides I would question that. I don't know the Ore well enough to know if you will also find yourself regularly plugging a sizeable chop and wind howling across wide open riverbanks, in addition to the tide? Or is it relatively enclosed so tide is the only factor?
 
Re: is 20hp enough for a 35\' fin keel yacht ?

I too agree that the 5 hp/ton is about right in most hulls of the length we are talking, and that assuming no compromise (ie an efficient drive). Unless, of course, one is a sail everywhere fanatic with unlimited time to wait for tides, etc.

If one cannot easily drive the hull to hull speed in moderate conditions then there is either something else wrong or the boat is underpowered.

John
 
Re: is 20hp enough for a 35\' fin keel yacht ?

I would be interested in your 20HP Beta if you go ahead! On my Moody 33 I have a knackered BMC 1.5 producing 38 HP with a 1:1 g/box - if you exceed 2500rpm you get cavitation. Because this particular boat cannot have a larger prop than 12" or 13" diameter; according to Nanni at the LBS I only require 14HP to attain hull speed, so your 20 HP would be fine.
 
Re: is 20hp enough for a 35\' fin keel yacht ?

We've got an 18hp (2GM20) yanmar in a 3.5t 30'er .. it does feel underpowered, but that may well be to do with the prop rather than the engine power - one day when I'm not fixing other things (got a lightning strike the other day, took out all the electronics!) I'll probably investigate.
However, comming back from the fleet review yesterday we sailed very well into a F6 with 3-4' waves - far quicker than using the engine! But then I've always thought a sailing yacht behaves better with sail up ...
 
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