1984 Kennedy nose-dives on plane

[flash1977]

Hello all. I bought a 1984 Kennedy Craft last year with 25 Evinrude on it. I have taken the Evinrude off and replaced it with 1992 Mercury 40EPTO. The first couple times I ran the boat, it trimmed out great and ran at 42mph (GPS). My wife and I went to the river last week, and the nose of the boat would trim up this time but then fall back into the water and it was planed out about mid boat.

What is possible problems? I considered that the boat may be warped, but that wouldn't make sense because it ran great the first couple times that I ran it with the 40hp on it. I am confused and definitely need help with this!

Thanks.

 

[Bondo]

Re: 1984 Kennedy nose-dives on plane

Ayuh,... Donno nothin' about Kenedy boats, but it sounds like the hull has devoloped a Hook in it...

Broken/ Rotten stringers maybe,..??

 

[Rscardina]

Re: 1984 Kennedy nose-dives on plane

sounds like you are poirposing (spelling)... or are you saying you were on plane and she then dropped??

at first i thought just human trim error..did you try trimming up to see if there was a change?

do you have the right prop? reason I ask is becasue if you get up and she starts to cavitate then you may lose a bit of thrust and then the bow comes down..

 

[flash1977]

Re: 1984 Kennedy nose-dives on plane

The boat comes up on plane and will stay there for about 30 seconds. After that she drops. It doesn't matter how much I trim the motor up, it won't bring the nose back out of the water.

I can stop and then start back and it comes back out of water only to drop down 30-40 seconds after running. The nose doesn't dive, where I am planing almost at back of boat, it is dropping back down in water to middle of boat.

I did drill a hole in the back of the boat under the transom (3/16") to see if there was water in the hull about 3 hours ago. It is still a steady stream of water pouring out of hull so it makes me wonder if that could possibly have been the problem?!

I am going to try to find the breach in the hull and repair that, probably put the Evinrude back on the boat, and look for a better hull to put the Mercury on.

It does feel great to get in this little boat and run with guys with 17' boats with 115hp motors on them though.....