Engine Height

[Bartine]

I needed to change my steering cable do to it breaking, and to do so I had to remove the engine to get clearance for the steering shaft. When I re-installed the engine it I decided to raise it up one hole, or about 1 inch. Where it was installed I was getting some porpoising when I started to get the motor trimmed up. I never could get the prop to blow out unless the bow was extremely high in the air.

It still runs good with the raised height, and the porpoising is reduced, but now I can trim it just about a quarter up through the trim gauge and the prop blows out. As long as I keep it below where the prop blows out it performs good. Is the engine too high now? Should I have more trim range?

This is on a 17.5 foot Four Winns Freedom 170 Fish and Ski

 

[JimS123]

Re: Engine Height

"Optimum" is where you maximize your trim and don't have blow out or porposing. Compare the optimums at the 2 height settings. If the new setting gives you a higher speed, then you are better than before. Just don't trim as high now.

 

[Bartine]

Re: Engine Height

I guess I would consider myself to be at the optimum height then, because I did pick up a couple of mph. Thanks!

Just wasn't sure if I should have more trim range or not.

 

[Boatist]

Re: Engine Height

That can be dangerous.
If it comes out of the water on a turn cancause the boat to filp over.
At the lower setting if it porposing just trim in a little and it will stop.

If your are going to have it that high do not go on large lakes or the ocean.
If you go over a followwing swell the prop will come out of the water the motor will rev to max RPMS and when it reenters the water the shock of the load can break flywheel keys or twist the drive shaft.
Either way your dead in the water and at the mercy of the sea until a TOW arives.

 

[109jb]

Re: Engine Height

Every outboard powered boat I have owned would porpoise if I trimmed out too far. As said, if it porpoises just trim in a little and it will stop. Actually, trimmed like that would be just about optimum in my opinion. I would say that the way you have it now the motor is too high. I'd put it back where it was.