15 horse on a O'25

[David]

I am currently running a 8 Horse Honda 4 stroke. This little motor pushes me around at between 2 and 6 knots. If I purchase a 15 will I be able to maintain 6 knots regardless of the tide and waves (within reason) or will I be wasting my money? Any thoughts? Thank you all -David

 

[Paul]

15 hp mariner

I have a 76 25'fin keel with a 15 hp mariner. I can run a steady 5 knots and push 6 without really screaming the motor. If I run it near full throttle it just makes more noise but doesn't get me much more speed. Its actually pretty fuel efficient. I'm guessing around a gallon an hour at the cruising speed.Good luck

 

[Geof]

Hull Speed, otherwise known as squating

I also have a 25 with an 8 hp outboard. If we run it at 3/4 speed or so we get roughly 5 knots in calm conditions. Any more throttle and all the boat does is squat by the stern.A 15 would be able to run at lower rpm's, but at anymore speed than the hull is designed for the stern will just probably squat and you would burn more fuel.Geofs/v Day-O

 

[Justin - O'day Owners' Web]

Agreed.

You're not going to go most faster, but I think you're asking if you'll be able to maintain the speeds you see in tougher conditions. To that, the answer is a conditional yes. First, as you recognize there is a limit. A huricane is still going to set you back. Second, many times more adverse conditions include steeper waves with shorter periods. If so, you may lift the prop out of the water regardless of the amount of power available. You will want an extra-long shaft on those days, and even then there will be a limit. Personally, I don't see the margin.Justin - O'day Owners' Web

 

[R.W.Landau]

I have an 8 with no tide.

I agree with Geof. Most of the time I am at 3/4 throttle for hull speed.Remember that hull speed is through the water. If you are fighting a 3 knot current, that is 3 knots under the hull. You will only make 3 knots over the bottom at hull speed.I personally think that the 25 transom will only take so much force. I would limit the HP to 10. I have been talking 2 stroke. It seems that the 4 stroke motors move the boat much easier than the 2 stroke. It is probably that they are quiter. They also use about half the fuel.If you sell the 4 stroke, let me know.r.w.landau