Using a 5hp on a Core Sound 17

[ecgossett]

I never even opened the throttle all the way to hit 7 knots. It handled nice but I reinforced my transom with some temporary wood wedged in the aft compartment.

The day before it sailed great with the motor on the back.

And no it's not my motor.

[MisterMoon]

I've got a six on mine. It's too big and heavy, but it came with the boat. I can run 8 kts with mine but I think it's capable of more. I think it's a little over-propped and not able to run to redline at WOT. I've got a friend who works for Yamaha who is going to see if he can find me a lower pitch prop.

It is nice to be able to have the option to go somewhere pretty fast when the wind dies.

[ecgossett]

Thats ok tomorrow I get to sail a Colgate 26 (with no engine), but this is the Indian Ocean so lots of wind, should be fun (only one reef point on the sails). The boat does have all the trimmings self tailing cleats, all lines leading aft, etc.

[Hirilonde]

What is a self tailing cleat? I know what a self-tailing winch is, but I can't even imagine a cleat.

[ecgossett]

My bad winch, blame my slip on 30 hours of jet ride and 11 hrs difference in time its 4 in morning here but 6pm BACK HOME.

[makenmend]

What would be a good schedule for reinforcing the transom to accept a 5/6 hp??.

I have the hull upside down ready to glass entire hull (seams/keel are taped).

MM

[MisterMoon]

Too late. Half inch transom with 2-by framing would be what I suggest. I strongly suggest getting an external motor mount so that it does not interfere with the mizzen sheeting.

[PAR]

2-by framing is way over the top for a 5 HP, even a 10 HP. All you need is an additional piece of 1/2" plywood as a pad on the transom, either inside or out. This provides more then enough meat for the clamps and spreads loads over a wide area. If you plan on lots of motoring about with this engine, a knee might be a reasonable idea, though if just puttering along when the wind dies and getting in and out of a marina, I wouldn't bother.

[Tom Lathrop]

2-by framing is way over the top for a 5 HP, even a 10 HP. All you need is an additional piece of 1/2" plywood as a pad on the transom, either inside or out. This provides more then enough meat for the clamps and spreads loads over a wide area. If you plan on lots of motoring about with this engine, a knee might be a reasonable idea, though if just puttering along when the wind dies and getting in and out of a marina, I wouldn't bother.

PAR is right, although remember that the top of the transom wants to bend aft and the bottom feels pressure forward under the thrust of a motor. Therefore a knee can work but is not the best way to reinforce a transom for a motor. More efficient in doing the job with less weight is to transfer the upper stress to the deck and its structure with a cross piece. I run 25hp or more on a transom of 1/4" thickness with no frame. There is a central pad to the hull bottom/keel and a cross beam at the top.

[makenmend]

Thanks folks, I had already doubled up on the transom, is now 1/2''and will add the recomended cross member at mid hight and top. I have an external motor mount which I may use, will see as to what rigging is best but I'm a good ways from that stage, did glass the hull today though.

MM

[hokeyhydro]

Check your transom clamps. You can screw them down only so much, so the clamp pad at the top of the transom needs to be thicker than the clamp max screw down. I doubt 1/2" will do it. Now the whole transom doesn't have to be thick, just the clamp pad area.

[wkisting]

Besides not overdoing it on the transom reinforcement, don't overdo it on the motor either. I use a 4-stroke 3.5 hp Mercury (weighs about 40 lbs.) and it pushes our CS20 at 5 knots with only one-third to one-half throttle. If you crank it higher, it can eke out 6 to 6.5 knots (7 with a tailwind), but it's not worth the extra noise and gas consumption. Notice that this is not far off the performance of a 5hp for considerably less weight and gas consumption. And the 3.5 still has thrust to spare for maneuvering against large waves or strong headwinds.

Unless you're going to go with a motor big enough to get up on a plane (which would surely impair sailing), there's not a huge performance difference in speed in the smaller hp motors on a CS series, but there can be quite a difference in weight, maintenance, noise, emissions, and gas consumption. I should say, also, that even though my CS20 sails great with our little motor in place, there is a small-but-noticeable improvement to sailing efficiency when I take even my small motor off the transom, so the less weight on the transom the better. In my opinion, that makes the 2 - 3.5 hp range the ideal compromise on motor size/performance/weight/convenience for a CS.

The one exception would be if you regularly need to motor for hours at a time, in which case the extra knot or two of performance for motors in the 5 - 8 hp range (and larger capacity external fuel tanks) may be very desirable and make a noticeable difference in cruising range.

[MisterMoon]

Agree with everything Wes says above. The *only* reason I have a 6 hp motor is because that's what came with the boat. It's got maybe 15 hours on it and I can't bring myself to sell it.