Engine mounting

[AQUASPORTOSPREY]

I have recently purchased a 2003 Aquasport 250 Osprey with a Yamaha 250 HPDI.
I noticed that it has been mounted 2 1/2- 3" above the transom rather than all the way down against the transom.

What does this affect?

 

[timberman]

Re: Engine mounting

wiki quote: Motor height on the transom is an important factor in achieving optimal performance. The motor should be as high as possible without ventilating or loss of water pressure. This minimizes the effect of hydrodynamic drag while underway, allowing for greater speed. Generally, the antiventilation plate should be about the same height as, or up to two inches higher than, the keel, with the motor in neutral trim.

 

[gss036]

Re: Engine mounting

The above comment is correct. I would assume they mounted it a little higher to help stop porpoising. You will need to learn to trim the motor up while running. The best rule of thumb that I have found is that the top of the engine cover should be parallel with the water you are running on. I had to do that on my SeaCraft23 WA. The transom should not have problems supporting and holding the engine.

 

[AQUASPORTOSPREY]

Re: Engine mounting

If top end is not a concern, but early planing would be nice, would dropping the motor down help this ?

Top end speed usually is not available as the seas here are not usually clam enough to open up that high.

I have noticed playing with the trim once on plane makes a big difference.

Dennis