How do I select a motor for my sailboat?

MrUnix · Apr 11, 2012

Your boat only has a displacement of 800lbs, so you don't need a whole lot of motor.. I had a Venture 17 that was the same size and weight and a ~4Hp British Seagull was more than enough for cruising around in Biscayne Bay and the Florida Keys. I did have a 7.5Hp (2-cycle) on it for a while, but that was overkill and I doubt it ever saw anything more than about half throttle. Weight should not be an issue with an outboard of that size as long as your mount is in good condition. And a long shaft is preferable in sailboats, although you _could_ get by with a short shaft if you really had to.

As a point of reference, the Hunter 23 came from the factory with a 5Hp 2-cycle engine, and it weighs about three times as much as your boat.

Cheers,
Brad

kloudie1 · Apr 11, 2012

Ward, if you are going to be in waves of any size, the long shaft will keep the prop in the water a lot better.. We used to sail a lightning with a short shaft engine and had to put folks in the rear to keep the engine driving in rough weather.. much easier with the long shaft.

c_witch · Apr 11, 2012

Taken from the Practical Encycopedia of Boating

Ward H said:
First time sailboat owner here. I have a 1976 Newport 17 with a drop down motor mount. I need to buy a motor for it but people I have asked have suggested a 3.5hp to 6hp to "the biggest I can fit".
How do I figure the hp needed? The previous owner said his 3.5hp pushed it OK but he only used it in lakes. I will be sailing in the bay behind Long Beach Island.
Do I have to worry about the weight of the motor?
I have instructions to determining long or short shaft.
What else do I need to know?

Best Regards,

Ward

In here they suggest 3 to 4 horse power per ton of displacement as being quite sufficient so a boat of your size would do nicely with a very small motor. Note that once hull speed is reached any further horse power is primarily wasted energy. You could probably do with a trolling motor in fact.

c_witch

Benny17441 · Apr 11, 2012

Don't know what the intended application was for that chart you found on line but a sailboat is a displacement hull which tends to go over the top of the waves and if those waves are 2 to 3 ft then the prop for the short shaft may spend a lot of time out of the water. A long shaft will work better. The only consideration would be in venturing into shallow water but I'm sure your rudder will ground before the engine does. Regarding the weight of the engine you should have no problems if you stay in the 3 to 6HP range as long as the motor mount is rated for the weight.

Rick Webb · Apr 11, 2012

4HP Long Shaft is a Good Choice

http://www.onlineoutboards.com/Tohatsu-4-hp-MFS4CDL.html

A smaller one would do but with the 4hp you get reverse, that makes a huge difference.

A friend was looking for a motor and the best price he could find was at West Marine

JRacer · Apr 11, 2012

My J/24 weighed 2750 # and was factory supplied with a 3.5 hp long shaft motor. Never in 30 years did I wish I had more horses. Although it's infrequent use and the fact that it was 2 cycle always was an issue with it being temperamental when starting. But also remember that we as racers are always concerned with weight and the 3.5 met the minimum required class weight for the motor. If weight were not the consideration, when I replaced the factory supplied motor, I would have gone with a 4 HP 4 cycle simply to eliminate the temperamental problem but instead went with another 3.5 2 cycle. Nobody made a 4 cycle light enough to meet the minimum weight required.

Stan Breaux · Apr 12, 2012

For what it's worth...
I bought the 6hp Tohatsu with the integral tank (for my dingy) from online outboards last year.
I'm not saying get 6hp -- I agree that is overkill.
My comment is about the integral tank -- I have found the motor very hard to start using just the integral tank -- I think it is because there is no way to prime it. It starts easily with the external tank, and the motor has given me no issues so far.

My advice -- order the external tank with it.

Crazy Dave Condon · Apr 12, 2012

Brad;

The Newport 17 if I recall was built near Gloucester, VA but the builder is deceased. I have worked on many and sold many small boats in my life time.

You could get by with a 15 inch shaft but where you are sailing a 20 inch shaft would be suggested in the event of following seas if the transom is higher. That will be a decsion you will need to make. Just make sure you raise the engine up before pulling out of the water on a trailer or it might drag on the pavement.

Anything over 5 hp is over kill for that displacement. IF you do considere, I would highly suggest a reverse control on the engine. As for the new engines, when shutting off, either disconnect the fuel line or turn off the fuel shut off to drain the fuel out of the carb. In additon, buy the additive that helps to detere ethanol that is put in. better yet, buy straight gas if you can.

Crazy dave condon

Chris Burti · Apr 12, 2012

We had a N-17...loved it...had a 4hp long shaft mexicali merc with intregal tank and found it to be perfect. You shouldn't really need an external tank and there isn't a lot of room for one in the cockpit as I recall.

Check the pin on the centerboard, the cable pendant on the winch and the as the centerboard is iron/steel, make sure you keep a good rust prentative coating on it.

Francois · Apr 13, 2012

No Reverse - No Problem

Ward H said:
The chart I found for shaft length was on the onlineoutboards.com web site. Maybe it was for fishing boat hulls.

If it matters, I will be sailing in the back bay off of Loveladies, Long Beach Island. Chart shows water as shallow as 1'. I also do not plan on being in 2 - 3 ft waves. If it gets that rough on the bay I want to be able to get into dock as quick as possible.

My wife and I just want to be able to go out on the water and cruise around a bit.

We do have to motor in and out of the lagoon and manuver around inside the lagoon so I think having a reverse gear would be a good idea. Also, an external fuel tank is prefered.

Being I will be in shallow water and bay chop, is a long shaft still a good idea?

All small motors can swivel around so the motor points backwards and then you are basically in reverse.

So do not let this bother you just make sure the motor can swivel 180 degrees.

kenn · Apr 15, 2012

We have a 5 HP motor on a 19' boat with approx 1200 lb displacement and it works well. So, 3 to 4 HP should work out well for you with your 800 lb displacement.

And YES to longshaft, chances are your rudder and centerboard will still be deeper, and if you're deliberately in the shallows, a good adjustable motor mount allows you to pull the motor up as much as you want.

Indysailor · Apr 16, 2012

Stan Breaux said:
For what it's worth...
I bought the 6hp Tohatsu with the integral tank (for my dingy) from online outboards last year.
I'm not saying get 6hp -- I agree that is overkill.
My comment is about the integral tank -- I have found the motor very hard to start using just the integral tank -- I think it is because there is no way to prime it. It starts easily with the external tank, and the motor has given me no issues so far.

My advice -- order the external tank with it.

I have a 4hp integral tank and have not experienced this problem at all. Starts up with no problems whatsoever. The only downside to this motor is refueling. You have to be careful not to spill. I use a cloth diaper to soak up spillage before it hits the water.

Also, on horse power, it all depends on what you need to do. I have a pretty small motor for a 3400lb boat, but it pushes the boat at hull speed. If I were on a bay, I'd have at least a 9.9hp.
We bought the smallest motor we could just to get us in/out of the marina, with reverse.

Chris Burti · Apr 17, 2012

Ward H said:
Chris,
Did your Newport 17 have the motor mount off to one side with the drop down mount?

Yes it did, mounted on the port side of the transom.

tkanzler · Apr 22, 2012

I had a 9.9 Evinrude 2-stroke on my Aquarius 7.0 (23 with stern rudder, instead of cassette through the cockpit sole) on an adjustable mount on the port side. What I discovered, this being my first outboard, was that the prop would come out of the water when things got rough, with the motor trying to overspeed. Pitching and/or rolling would bring the prop close enough to ventilate, or come right clean out. Not good.

Not a problem in calm water, of course, and I don't know if the height was correctly set by the original installer in the first place, but when I most needed that outboard, it most wanted to not stay in the water.

In my humble opinion, get a long shaft, set the adjustable mount one notch up for normal operation and motoring in shoals or beaching (with the boards up - may also make the OB tiller easier to use), but have the ability to put it all the way down if you get caught in some rougher water than you'd like. Trying to run for cover when the OB is sucking air isn't much fun. It happens, and it's prudent (IMO) to allow for it. Best of both worlds, and cheap insurance.

Oh, and for a boat that light, I'd think the smallest OB with reverse gear is what I'd be looking for. Hull speed is hull speed, so the only use for any extra power beyond what that takes is to push against wind. 4-5 hp should be plenty.

Ed_S · May 15, 2012

I'm looking to replace an outboard on a Hunter 216 which has a displacement of 1350 lbs.
The long shaft makes sense for this boat. I plan to take the boat on the Merrimack River where the currents at times can reach 7+ knots. I've been told to use a 10 to 15 Hp outboard. Most often this is overkill and most of the time I will try to avoid the river when the currents are running this strong which would support using something smaller such as a 5Hp. But the being prepared side of suggests a bigger motor. Can you advise on what the appropriate size should be?
Thanks