91 Johnson 90hp dies at idle

[chillywillie]

Fishing season has been going real well this year (1st and 3rd the last 2 weeks) but my pontoon is giving me fits (which means my wife is giving me fits too ). Motor runs good at higher RPMs but when it drops down to about 1100 RPMs, it bogs down and dies out. If I try to rev it back up, it is slow to respond. When it gets down to 1100 RPMs, motor makes a sporadic "off" sound, like it's sucking air or not getting fuel.

Replaced the power pack (because it needed it) and the 3 ignition coils. Changed the plugs, replaced the fuel line and bulb. My guess is that it's probably in the carbs, maybe the low speed jets clogged up? Anything else someone can recommend I check over? Any chance it's the fuel pump or something else? If I can't figure it out, I'm just going to trailer it somewhere and have a real mechanic look it over. I was going to try new gas (gas I have is from very end of last year with stabilizer added) with some Seafoam to see if that helped.


Thanks!
Willie


Modified by chillywillie at 2:53 PM 6/12/2009

[ChampioNman]

A model # would help. I can't remember a 90 of that year having 3 coils as it is a V-4.

[chillywillie]

Sorry, typo it's a 60hp! I fixed the title too....

[ChampioNman]

Sounds like a sync n link would be in order. That is when you sync up the linkages and timing on the motor. A manual is a must for this.

[ELGIN]

Sounds like a carb rebuild or low compression.

[chillywillie]

You were spot on Elgin! Compression was:
1st: 12 lbs
2nd: 20 lbs
3rd: 115 lbs

Pull the head off, and the gasket was shot between the 1st and 2nd. I guess the previous owner must have lost a head bolt and used a large screw instead and the gasket failed right next to that screw. Cylinders still looked really, really good (was rebuilt a couple of years ago and the cross-hatching is clearly visible) as did the block & head. Cleaned it up, new gasket and the compression is now:
1st: 100 lbs
2nd: 100 lbs
3rd: 115 lbs

So she's still off a little but close. It was also nearly impossible to start before, but now it literally started first turn of the key.

2nd of day of 2 day tourney tomorrow (although with as bad as today was I might as well stay home ), but hoping to dump the pontoon in afterwards to run it a bit and do some fine tuning.

Thanks so much for the help!
Willie

[ChampioNman]

Good deal!! Elgin is a good un!