Johnson 155 drops RPM suddenly

[mrom1234567]

I have twin Johnson 155 commercial motors.<br />At crusing speeds with the boat properly trimmed and about 3-4000 rpms, one motor suddenly drops to 1500rpm even though the controls are not touched. Does anyone have a clue? I can live with this, but I was wondering if it could be a fuel or carb. problem.<br />Michael

 

[hondon]

Re: Johnson 155 drops RPM suddenly

That's a big drop to consider this just one cylinder falling off.Next time you are out take a timing light with you. Hook it up ready to work, and when the failure happens, move the inductive from wire to wire while pointing the light at your face.This will tell you if you have an intermittant ignition failure.There are certainly other possible causes, but this test is easy although a little dangerous.Wear your PFD, and hang on.

 

[Terry H]

Re: Johnson 155 drops RPM suddenly

What year are the motors? Could be a overheat problem on one motor...<br />just a Thought