Four Winns Boat Porpoising

[dippasan]

Originally Posted by Woodsy

dippasan....

A boat porpoises due to overtrimming the drive relative to the speed the boat is traveling. Too slow + too much positive trim = porpoising.

Another cause for porpoising is a nasty hook in the hull. You can take a long straight edge to the bottom of the boat to see if this is the case. I doubt it though. If thats the case its not a cheap fix.

You didnt say who made the powertrain... I assume its OMC? In anycase I would follow the advice above and look at changing your prop. Not sure what the prop size was originally, (prob somewhere around a 14.25 x 21) but if you can find that out that would be a good place to start. Def go with a 3 blade stainless steel prop over the original aluminum.

Here is a link to Four Winns website... http://www.fourwinns.com/past_produc...20(p12-16).pdf

Woodsy

Thanks for the link and the info. It is an OMC drive with the 5.0L engine. I just got the # off the existing prop and its a #3850300 which I cross referenced and seems to be a 15X17X3 prop. Also the boat topped out at about 47MPH which was a bit disappointing. Thought it would be more like 50 MPH with 215 horsepower.
Would you suggest the 14.5 x 21?

Thanks again