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bad porpoising problem

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Karl1964

New member
I have a J14 Carolina Skiff that I just repowered with a 25hp suzuki. It replaces a 95 model 25hp evinrude. This boat at about 1/4 throttle starts to porpoise very badly with just me in it. If I put another person in the boat with me it calms the issue a bit but the faster I go the worse it gets. This is with the engine trimmed all the way down and with the engine mounted as low as possible on the transom. That puts the cavitation plate even with the bottom of the boat. Does anyone have any idea on a way I can fix this issue? Thanks.
 
The 2 stroke Rude is about 20 lbs more than the Suz (looking at 15 inch shaft). Assuming both motors have same length lower

In other forums folks have said that moving weight forward helps. Like getting a longer fuel hose and move the tank. Some use a 4 blade prop. Been a few that installed Bennett manual tabs and it fixed it. Anything like a dole fin or tabs will help but also produce drag which will increase fuel burn slightly
 
Likely bad weight distribution. Move more weight to the bow. If that doesn't work, think about installing trim tabs.
 
If you have access to sandbags it will give you an idea how much weight you need. Start with two and start dumping sand overboard until you find what works.
 
Adding weight is counter productive.
Transom angle is typically about 11 degrees if I recall. That allows the engine to trim down past parallel with the bottom. Check and see about yours. Compare with other typical boats.
Maybe a set of these would help? $70 is better than hauling ballast weight until the end of time.

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