12' Alumacraft wont plane?!

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arob8924

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I have a 12' mod v alumacraft with a 9.5 hp Evinrude Sportwin. With the motor mounted on the original transom the motor just sucked the stern down into the water. The cavitation plate was about 4.5" under the hull so I built a transom extension. With the new extension, the cavitation plate is now lined up well. With just me in the boat at the back end it just sits nose high with the motor on full throttle. I had a buddy sit in the bow and it helped, but still didnt plane completely. Im thinking of putting a hydrofoil on it, since a friend has a spare one lying around. Ill post pictures but does anyone have any other advice?
Also i should mention I have the gas tank up front and im not overloading the back end. When i am sitting with no motor the boat sits level. Thanks for any help!
 

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Have you tried playing around with diffrent trim settings on the motor? That motor should easily plane a 12' boat and if trimmed properly you should be fine with just you in it and gas tank in front. When I run by myself i have to tilt motor down more or it points the bow straight up but once in the right position it planes nice and easy.
 
I have messed with the trim, trying each of the 4 or 5 settings it has and it seems to work the best while the motor is trimmed all the way down. I dont know anything about different props for this engine but could that be the issue? Also i should mention i have only tested the boat on a small river... but whether im going up or downriver doesnt seem to have much effect on the planing ability. It feels like there is just too much weight in the back... I weigh 250 but ive seen videos of similar or bigger sized guys up on plane with smaller motors! Im kindof at a loss... Im thinking the hydrofoil may help but it seems like i shouldnt even need one.
 
Im 230lbs and an 8hp on a 1436 use to plane out with just me in it. Your old 9.5 is probably about even with the 8hp in power as the old motors were rated diffrently. Your boat may be waterlogged adding unecessary weight. Hard to tell from pic but if your back bench is foam filled that foam could be holding a lot of water if its older.
 
After a quick search looks like only prop available for that motor is a 8 1/4x8 so even if a prop change could help it mighy require a prop shop to alter or custom make one for you.
 
I've been in boats that had the same problem and ended up pulling the trim pin out completely so the motor could go down all the way and that solved the problem temporarily. I don't care for those whale tails but it may be the solution in your case. I'd definitely check on the water logging situation mentioned above though.
 
Thanks for all the advice! Tomorrow I'm going to put my backup prop that has a screw in it because it was spun to make sure my current prop isn't spinning at all. If that doesn't make a difference I'll try the hydrofoil, then check for water logging. I'll post what I find! If it is water logging... What is the best way to test it? And if I replace it can I rip out the old and fill er up with pool noodles? I've seen a few guys do that on this site.
 
Yeah I just put a carb kit in it and new plugs and it was running like a top. But just for grins I'll check that tomorrow too.
 
Good mechanic can add some pitch. But might need to take some out. Depends on rpm. Multi meter or tiny tach.
 
We'll this weekend I installed a hydrofoil and she planes with ease now! I'm thinking the combination of the small hull and the weight being so far back was just too much for the motor to get out with. I'm still going to investigate the possibility of having waterlogged foam in the seat. But for now I'm happy to be away and fishing! Thanks for all the advice!
 
A 9.5hp is just barely enough to plane that boat with a full load. I would suggest a simple, removable PVC tiller extender which would allow you to sit, stand and move around at will to best shift the weight. Hyrdofoils/"whale tails" are cheap-o, $20 gimmicks that simply mask a bigger issue. After all, there's a reason not a single manufacturer uses or recommends them, nor will you ever see a pro with one installed on their motor. Instead, install some proper fixed or adjustable trim tabs which are legit modifications to your hull. Plus, if you drill holes into the anti-vent plate you'll void the warranty. Then there's the part when every at the ramp laughs at you when your "whale tail" catches an edge/rock/log and snaps your anti-vent plate, or turns into a giant, underwater weed rake :/ Find out what's really wrong with your set up, then fix it properly ;)
 
I know exactly what's wrong. The boat isn't designed for an outboard. The transom is only 12-13 inches deep and I built a transom extension to fix that issue .. The back end of the boat is tapered in much more than others of similar size. The hydrofoil is just allowing me to plane. In other words, I'm doing what the boat isn't designed to do, so running an ideal setup means buy a new boat. I'm happy fishing from this one until I can upgrade.
 

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