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Stalls when semi-warm 1999 90hp

C

customsportsman

New member
Hi fellas,
New guy here. Great site. Lotsa knowledge here, and I think I need to tap into that knowledge. I have a 1999 Johnson Ocean Pro 90 HP V4.
I bought it new. I've maintained it well all these years. Every year fresh gear lube, nothing but OMC 2 cycle oil, properly winterized, water pump impeller changed as necessary, etc.....

Here's the issue. The motor ALWAYS started right up whether cold or warm. I had trouble a couple of years ago with a bog, and at the suggestion of a shop, I removed the anti siphon valve, and the bog went away. We use the boat for a lot of skiing, so bogs are unacceptable. This year, the motor starts, then stalls. Then when it starts, for about a minute, it barely idles, then runs fine. If we sit on the lake for a spell (like an hour or so) the motor will do the same thing, THEN the motor will NOT accelerate. If I idle for a few minutes, it will be fine. High speed is fine, no loss of power, no overheating, etc... Also, sometimes there is a pass-thru misfire upon hard acceleration around 1000-1200 rpms.

The gas was in it since October of last year (stored with OMC fuel stabilizer). Burned half the tank, topped it off with fresh gas, no help. Put in new plugs...no help. I'm not a fan of going in and screwing around with adjustments/settings aimlessly. The ignition is all solid state, so I see no need to screw with it.

Remember, once it is fully warmed up, it is FINE. Do I need a water separator? The boat didn't come with one, and I bought it new.
Any help is appreciated.

Thanks,

Tim
 
Re: Stalls when semi-warm

The fact you had to remove the anti siphon valve to alleviate a possible restriction issue the last time is indicative of a fuel contamination or restriction within the tank or pickup tube. A sticking valve is highly unlikely since most will stick in the close position and prevents the engine to run period.
First and foremost, start the process of elimination, connect up a portable fuel tank and test, if all is well, simple clean your tank and its pickup tube, there is a mesh at the bottom of the pickup line.
If you still have a problem, the contamination and bad fuel has sinceh moved on to the carburetors, you will have to service the carburetors, evidence of excessive muck in the carburetors will require a serious cleaning and rebuilding...
Question is your on board tank a poly or aluminum ?
 
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