HP expectations

[dchris]

I have 17 ft bass/ski boat that is need of a new motor. The boat is rated at 70HP. Are there any charts or ways to estimate performance for different size motors? What could I expect out of a 30HP compared to a 50HP? I agree more is better in this case, but the cost sure goes up fast.

 

[Bob_VT]

Re: HP expectations

Powering a boat with less than 50% of the max rated power will usually yield poor results

If you do a search for Theoretical Speed Formula you might get some ideas.

If the 30hp is all that you have then you have a fishing boat that will get there but not quickly.

 

[ezmobee]

Re: HP expectations

The Johnson/Evinrude 3 cylinder motors (60-70HP) are some of the best horsepower to weight ratio motors you can get. I'd look hard for a nice used Johnnyrude 70.

 

[Silvertip]

Re: HP expectations

The general rule of thumb for acceptable performance is not 50% but 75% of maximum rated HP. If your boat is rated for a 75 HP motor, I doubt that a 30 would even get it on plane. And in that example, using the 75% rule, a 50 HP motor would be the absolute lowest HP that boat should have. Of course hull design and weight enter into the picture as well.