2000 Johnson 90hp Running Rough

[mendy]

First time I've had issues with my outboard. After a smooth first run out and most of the way back, after stopping and making a couple drifts with the engine off and then restarting my 2000 Johnson 90hp died at idle (which it had never done in the past) and then proceeded to run quite roughly up to about 3000rpms. Once I really put the throttle down she seemed fine. This continues now a week or so later.

The mechanics at my marina think its a fuel problem inside the engine though they cant really seem to pinpoint exactly whats going on. The plugs have been changed, the carbs cleaned, compression is fine, timing fine, etc. I am starting to get frustrated and am going to give them one more chance to find out whats going on before taking it to another mechanic--anyone know a good OMC guy in the Boston Harbor area?

Also, anyone here more mechanically inclined than me have any ideas on what might be going on???

TIA,

John

[mctrout]

same thing with my 2000 115 johnson. wont idle once it is warmed up and also will break up at high speed. has to be a fuel problem and easily could be re-fouled plugs, fuel pump or bulb, oil injector system, etc.. I am no help here unfortunately. also could be a faulty plug wire. run it and see if any of the plugs are wet after. kink in the fuel line somewhere, clogged fuel filter, bad gas, etc.... please let me know what you find out
thanks
Brendan

[JakeFF]

John..if its not to far for you...Chips Outboards in Pembroke..great guy knows his stuff...not sure of the number but in Yellow pages. Been there for years.

Good Luck

Bob H

[kayaker]

Except for its operation at idle, my 1997 40-hp Mercury had a similar problem. After several incorrect diagnoses, the cause was traced to carbon buildup in the exhaust system, causing a loss of compression. Several ounces of crud were removed, and the motor hummed.

[Mark Cahill]

Look for particulate matter in the gas. I had a lot of trouble in the past with varnish in the gas. (it's a product of broken down old gas).

One of the problems is that there is a screen under the nipple that comes off the tank. It will fill with varnish and starve the engine. But when the engine stops, it drops back down the tube. So then you start it again, and it runs. Then cuts out. You may want to pull the nipple on the tank and check the conical screen filter that's down inside the tube coming out of the tank. At higher rpms, it will some times have enough suction to pull the junk through the screen.