Weak Johnson 150

Randy,

I have a 1990 Johnson 150 on a 2100 pound Crestliner. Rebuilt the carbs, new plugs, fuel filters, compression even 90 all 6 cylinders, all cyl firing. Idles smooth, and starts to accelerate, but then levels off around 3500 rpm and tops out at 15mph. Just pushing water from there. Haven't touched ignition or timing, didn't understand what the book explains. Need some ideas on what to do next, or how to check timing components. Thank you!

 

Sounds like it is severely “over propped”. Have the motor tested on a test wheel. This will verify the engine is ok. Most dealers have these, older dealers anyway.  

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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