I just took out my beavertail al frame that I moded replaced the original engine with a 9 hp subaru. it's on a 1436 waco went out and ran pretty good but the prop won't stay where it needs to be. it'll be going good for a bit the flys up outta the water unless i pull up hard on the handle the whole time lol .I tried bending the tab up I'm wonder if maybe I need to add a longer tab since I made it of all aluminum what say ye of more knowledge thanks for any input

what size motor was on there before?

I make a tab out of aluminumfor my aluminumframe motors that i then bolt to the cav plate. I bend it in the vise,off of the frame. Much easier than trying to bend a welded cavitation plate. Mark F. Cheney

Bend it up some more. That the correct way to cure popping out of the water. Mine is bent fairly noticeable. But on plane full throttle you can let go of the handle & it will stay put now.

I think I may have screwed up I could swear it was exact same angle as old plate only reason I moved it was for a bigger prop anyway when I checked it now it's at 21 degrees to the shaft and I'm thinking it should be at 15

I asked the motor size, because If you went up in hp a good bit, the motor is probably heavier than the other motor you had on there, causing the frame to not be balanced.

I had a friend put a bigger motor on his longtail.
Went from a 23 to a 35.
He had to add some counter weights to the cav plate to balance it.
Id also try that

The old motor was a 6.5 specs say old was 40 and this 9 hp is 46

well, I kinda do believe you will have to offset that weight somewhere on the frame of the longtail.

Ok I cut the wedge and got it down to 15 degrees with about 3/8 between the cav and prop. I got some 0625 ss sheet to bolt on for a trim tab just trying to figure out what length I should do for the tab. wondering if I should just bolt it on as is or if I should cut the inch tab already on there off and then bolt the trim tab on top which will put it at 1/2 inch over the prop what do you guys think ???? Thanks for any input

Well back to square one put a longer tab on went out and dam near had it bent to 90 degrees no change as soon as I get on plane out of the water she comes doesn't matter if I'm alone or have someone up front kinda scratching my head as what to do cut it off and reweld in different position? ???