91 Johnson 120 Surging at WOT

[mattb4rd]

I took the boat in to the mechanic this week. He cleaned and adjusted the carbs, installed a fuel/water separator, fixed various gauges and some other minor things. He did test run it in the river before I picked it up.

This morning I noticed a distinct improvement in the way it cranked, idled, and ran at full speed. 500 more RPMs than what it could manage before the adjustments.

HOWEVER .. about 20 minutes into our run the motor started surging badly. I throttled down to a stop and checked the water stream, the priming bulb, and even looked inside the bilge to check for a collapsed fuel line. All looked good.

I tried again .. same thing .. as soon as it hits WOT and is trimmed out it starts surging. I turned around and ran back to the dock at 4500 RPM and it did fine.

I've got a call in to the mechanic and will be taking it back in to him, but I'm anxious to get an idea of what's wrong. Pretty tough to convince the wife that "this is life with a boat" when we just spent nearly 400 bucks on the repair.

Thanks,

 

[ezeke]

Re: 91 Johnson 120 Surging at WOT

If not a fuel restriction, then probably an air leak, might want check all of the hoses at the engine and make sure that they are snug.

 

[mattb4rd]

Re: 91 Johnson 120 Surging at WOT

After sleeping on this more I remembered one more detail. There was oil on the surface of the water immediately behind the motor while I was idling and on the cell phone (trying to call the mechanic).

I smelled the water coming from the water pump and it was ok, so I think I do I have a fuel leak that becomes an air leak at high speed.

Hope my mechanic calls me back today and can fit it in this week.