My buddy has an older 17' Aquasport, running a mid 90's Yamaha 90hp on it. He put on the Doelfin, and is still having a rough time getting on plane. We were out a couple of weekends ago, and I was looking at his boat while he was next to me. It seems like the engine should trim down lower, almost following the line of the transom. Mine does, but his does not? Do they make some kind of wedge or adapter for this type of situation? He had dead motor, and traded it toward a rebuilt, and the boat yard that sold him the motor installed it for him.

Anyone got any input??

nevermind. you already put one on..... had a link to the dang fin.
could be the installed motor angle needs to be adjusted? I assume on a 17' it's not adjustable while driving? Maybe it just needs to be angled an inch or so back. just a few degrees can make a ton of difference

they make wedges that will give you more negative trim, also check if there is a pin in there that is keeping the motor from reaching full downward travel, where did he buy the motor, if it's not right the boat yard should make it right, I know that's what we do where I work, whatever it takes to make the customer happy, no reason that boat should need a doelfin

Thanks guys, I did some research online and saw the wedges. I think that may be the way to go.

Freebie it was in Weymouth, I don't want to put the name out there, cause other than that he is very happy with the motor and what it cost him.

I hear you on not mentioning the shop, with the wedges he will probably not need the fin

First thing to check and maybe you did.
There is a "stop" pin that can be moved further down, I am assuming
it is already down to the last position though, but just in case....

The cavitation plate should be able to be parallel with the line of the hull. If it goes less that is even better.

good luck.

The Stop pin I believe is out, and the motor is trimmed all the way down, I believe it is the angle of the transom. :)

How's the prop pitch? Is it getting close to max rpm at wot while lightly loaded? I ask because that boat should not need negative trim to get on plane. OTOH, a 2" diff in pitch can make a huge difference in getting on plane.

Not sure about the prop, but I talked to my buddy and he says he has water in the fuel. He found it out because he could not get the thing running for very long distances. I asked him what his max rpm was before the motor cut out and he was not sure. He is pumping out the tank today, and he cleaned out the bowls on the carbs already. I suspect this might be the problem..