1997 Johnson surges a high speed

[joesofa]

I am running twin 150's. The port engine had been sneezing/killing at idle after warming up. Recently it started to surge at high speed. It seemed to run fine at 1/2 throttle. I was told that the sneezing/backfiring was associated with running to lean. After adjusting the carb mixture slightly the engine seemed to idle just fine even after warming up. As far as the surging is concerned, I had my son continuously but gently squeeze the primer bulb while running. The surging went away and ran at 100 rpm over the other engine. After my son let go of the primer bulb, the surging eventually returned. Both engines share the same tank and fuel lines up to the inline filter/water separator. Any advice would be appreciated. Thanks!

 

[joesofa]

Re: 1997 Johnson surges a high speed

I decided to drain the carb bowls. All but 1 seemed normal...full of fuel with no trash. However, 1 of the six carbs barely had any fuel. After removing the carb, I noticed that the needle valve was in bad shape. The plan is to rebuild tomorrow.

Does anyone respond to Cadets? We all have to start somewhere.

 

[tashasdaddy]

Re: 1997 Johnson surges a high speed

yes we respond to every one we can help, if we have something to contribute. pumping the bulb leads to think fuel restriction, and the needle valve could be causing that, also a weak fuel pump. also running 2 engines off the same lines and filter could also, unless they are over sized to accommodate the amount of fuel need for both engine.

 

[joesofa]

Re: 1997 Johnson surges a high speed

Thanks for the response. I rebuilt the bottom 2 carbs as 1 had the bad needle and the other was the one that had a suspect spark plug (i.e. white ceramic). Took the boat out and the engine screemed to 5000 rpm. The sad thing is that its twin would only get up to 4200-4400 rpm. I believe that both of them were running in that range when I first got the boat. Anyhow, I guess I need to look at carbs on the slower engine.

Do you recommend seperate fuel filters?