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Go Back   SailNet Community > On Board > Gear & Maintenance > What size motor for a 20ft trailer sailer?
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Thread: What size motor for a 20ft trailer sailer? Reply to Thread

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Topic Review (Newest First)
12-21-2011 01:40 PM
rrh I have a Watkins 23 (2500 lbs). I have a 6 hp Johnson 2 stroke. It is all I need, except if you need to stop fast :-) I hardly ever run over 1/2 to 2/3 throttle. It has a "weedless" style prop though and that makes it lacking in reverse. I'm pretty sure that I saw somewhere that the standard motor offering was 2 1/2 and the upgrade was six.
12-21-2011 01:02 PM
MarkCK I use a 6 hp on my 1500lb 20' boat. If I had to buy another one I would probably get a 4hp motor. I do sail on an inlind lake where conditions never get out of hand. If I was in an ocean enviroment I would probably opt for the 6.
12-21-2011 09:25 AM


I have 4 hp mariner on my 21 ft, weighs 1400 lbs and rarely need much throttle. I don't sail in the sea, but can't imagine it wouldn't be enough if prop stayed in water.

good luck

12-21-2011 04:08 AM
CoasterNZ Thanks for that - good advice. I'll stick to long shaft.

High thrust - can anyone give me an idea of the dimensions and range of pitch ratio I should look for in a prop?
12-20-2011 09:11 PM
bjslife I had a 9.9 Johnson long shaft on my 1969 Venture(mcgregor) 24' and never worried about tide or current. It was easy to lift also.
12-20-2011 06:08 PM
Originally Posted by CoasterNZ View Post
What size motor for a 20ft trailer sailor? Should be a simple question, but maybe not.. The national trailer yacht federation stipulates a minimum of 6 HP, but I'm wondering if I'm out there in the poo one day in 30 knots, whether 8 HP could be wiser?

But a light motor is good as it will get put on and taken off lots, and is easier for everyone to raise and lower on the adjustable transom, which the current 9.9 HP Suzuki isn't. Wondered about 4 strokes - heavier but cleaner, more efficient, quieter (vibration?) 6 HP 4's tend to be single cylinders and haven't heard wide praise for them. The propeller pitch is the other consideration - and simple suggestions?
I had a Tohatsu 3.5hp 4 stroke on my trailer sailer and it was a great little motor. Sipped fuel, reliable starter, good power. I'm sorry I sold it, it was way better than the Suzuki 2.5 I have on my inflatable dinghy now.

I never noticed much problem with vibration. I tended to lock it dead ahead and steer with the tiller, so I was never holding onto it for long.

As we are likely to see more bodies of water closed to 2 strokes, I think getting a 4 stroke makes sense if you're not too sensitive to weight. 10 or 20 extra lbs isn't going to bother you as much as it would with an inflatable dinghy.

I bought the Tohatsu as, at 43 lbs, it was a good tradeoff, power vs. weight.
12-20-2011 04:49 PM
kwaltersmi I agree, 8hp is overkill to be sure. Cavitation becomes a real issue when things get snotty and you have to motor. Better to avoid the snot or learn to sail in it.
12-20-2011 03:39 PM
zz4gta I use 3.5 on a 25' 3000 lbs boat. Works just fine. In a sea way, an outboard ain't gunna move you anyway. Hope there's wind, and sail in.
12-20-2011 10:33 AM
BarryL Hello,

when I had a Catalina 22 I used a 4 HP motor and I never wished for more power. The boat weighed about 2000 lbs, so I would say that WanderingStar's formula is correct.

Lastly, a long shaft is more important than more HP from a short shaft. A big motor that comes out of the water in waves / chop won't work as well as a 4HP that is in the water when you need it.

12-20-2011 10:18 AM
WanderingStar The old formula was 1hp/500lbs. Four horse should be fine. I rowed my 20' keelboat, then used a 45lb thrust trolling motor. Neither method worked into the wind, but then I just sailed.
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