Transom depth and mounting

[Izzy650]

mad:I recently boat a 17' Gregor aluminum skiff the question I have is the transom is 22" and I mounted a 1990 2 stroke 40 hp yamaha with a 20" shaft. When I plane I can visibly see the anti-cavation plate I been told by friends the outboard is to high and i should lower it. The question is theres two fins a small one 2" above the anti cavation plate which should be even with bottom of the hull. I do get some cavation when turning hard and on plane or when backing. I can also almost see the prop when planed out. Any help would be great and thanks for a great boating site.

Izzy650

 

[Texasmark]

Re: Transom depth and mounting

No biggie. Get a high performance prop, will probably be in SS to get max goodies and go for it. Read the specs, talk to the suppler and get the best one that runs close to the surface/at the surface. The 40 hp may put you in a seldom used diameter which would/could complicate your efforts but give it a go. I know there are people on here that can advise you.....Walleyehed for one. He has a Sticky at the top of the "Props" section. Contact him.

Usually 1" is tops for anti-vent above the water at WOT and suitable trim position for general purpose boats.

Other option is to chop 1" off the top of your transom to lower your engine.

HTH.

Mark

 

[scoutabout]

Re: Transom depth and mounting

It doesn't sound like your situation is too bad if the boat is running and handling well for the most part. I would be concerned that you might be over-revving your engine if the prop is actually biting air while wound out. Do you have a tach and can you check it against the WOT RPM specs for that motor?

 

[Izzy650]

Re: Transom depth and mounting

It doesn't sound like your situation is too bad if the boat is running and handling well for the most part. I would be concerned that you might be over-revving your engine if the prop is actually biting air while wound out. Do you have a tach and can you check it against the WOT RPM specs for that motor?

I don't have a tach hooked up yet but should soon. I need to so I can switch around props to get a little better performance. The motor sure doesn't seam to be over-revving but it got hot the othe day after running at 3/4 throttle for 40 min. Or so I ran it the next day for a hour or so and it was fine the only difference was it was fairly rough out and the day before was like glass. I was thinking that being so close to the top of the water on a calm day it was getting some air but the pisser seams strong when watching it.