Sleekcraft Porpoise

Dear Sir,

The other day I bought a 20' Sleekcraft tunnel hull with a 200hp Yamaha. As I tested it out on the water it wants to porpoise from 20mph up to 45mph. I tried adjusting the trim but cannot get it to stop. It smoothes out at 45mph up to 60mph. The motor is mounted on a Gil Bracket with the prop shaft set at about 2'' below the bottom of the transom. Is it set too high to get a smooth  ride at slower speeds? Do I need to drop the motor down? Please e-mail.

Thank You....Greg S

 

Greg, 

That is a characteristic of the mod-VP tunnel of that era. The boat was a jet boat by design. Maybe try a Cavitation plate whale tail. This may stop the bounce at low speed.

Randy

 

 

Please submit whatever questions you have to IHRTechTalk@yahoo.com.  All questions and answers selected will be displayed on this page as they come in.  Note: though all boaters are welcome, priority may be given to I.H.R. members.  Randy can not be held responsible for any advice given.  Though his information and expertise is second to none, he has no control over what you do with your boat.  It is up to you to boat safely and act responsibly, and his advice is only to be used as a guidance for your high performance boat/motor of which you are the one responsible for the risks involved.

Thanks,
Mark C.

 

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