81 Johnson 155 laking power

[115johnson78]

The boat had a 78 Johnson 115 but, had two cyl. that was low compression. It didn't run the best at idle but would run the 17 foot deep v about 30 mph loaded down. So I had the motor swapped out with a 81 Johnson 115. It ran awsome, had more power, plained out faster, and all that good stuff for the first 20 min. then all of a sudden it seemed to bogg down, would take forever to go from idle to 4,000 rmp wide open(before it would tach around 5,000 rpm no prob) whitch I was cruzing at 4,200 when it just kinda stalled out. Any thoughts???? It has a glass fuel filter and it doesnt stay full all the time but runs the same even when it is full.


Thanx.

 

[emdsapmgr]

Re: 81 Johnson 155 laking power

Possible that the engine is losing spark to one cylinder after the engine warms up-a common problem for a weak ignition component. Use an inductive timing light to check for solid spark on all 4 plug wires when the engine starts to act up. Do the testing when the engine is under load, like idling in gear at the dock.

 

[115johnson78]

Re: 81 Johnson 155 laking power

I did what you suggested(with the light, looked good) and took the boat out and ran the same at no pulling power. I think that maybe some dirt in the hispeed orfice in the carbs? I there a way to clean with out removal of the carbs?

Thanks for your help.

 

[emdsapmgr]

Re: 81 Johnson 155 laking power

The only way to really clean the carbs is to clean the carb passages. That means complete disassembly, including the jets. An aerosol carb cleaner sprayed through the passages will get any dried fuel out of the airways.

 

[115johnson78]

Re: 81 Johnson 155 laking power

That's what I thought. Thanks for the great advice.