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1988 15 HP Johnson starts, won't keep running

T

The Waco Kid

Member
The 30 year old 15 HP Johnson starts! Runs hard and fast. But not for long. I did not time it, but seemed like 1 to 2 minutes. Dies, won't restart unless I pressurize with the bulb on the gas line. New, ethanol free gas in a nearly new plastic tank and hose. 50/1 mix with synthetic 2 cycle oil. If this was a car I would suspect fuel filter. Or the screen at the intake in the gas tank, with sediment in the tank. Tank is clean. Any advise?

Also, while it was running a gray goo was seeping out the propeller opening. Motor was hooked with muffs to the hose, mild pressure. Do I have leaking seals around the prop shaft? Seems to only leak when running.

Thanks in advance!

The Waco Kid
 
Boobie said:
Sounds like a bad fuel pump. JMO.
Click to expand...
That would be my first thought too. It's running on the fuel in the float bowl until it runs out.

Is there a vent on the fuel tank? If that's not open the little pulse pump diaphragm has a hard time drawing against a vacuum. If the problem isn't a fuel tank vent I'd rebuild or replace your fuel pump.

The grey goo most likely isn't any problem, that's probably old unburned oil deposits in the exhaust tube that are getting flushed off.

On a side note, I would strongly encourage you to run the motor in a tub of water instead of on muffs. This lets the water pump do its job and lets the motor run at the correct temperature instead of forcing too much cold water through it. Also the tub of water will create back pressure on the exhaust and lets the engine run at the proper idle

Here is the parts diagram for your fuel pump. Repair kit is $12, complete pump is $66.
http://www.marineengine.com/parts/j...vinrude&section=Fuel+Pump+-+Rope+Start+Models

KJ
 
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Carefully take the pump apart and lay in on the bench exactly as it comes apart take note of the springs and nylon pieces on the springs. Its real easy to put together wrong. Also replace the fuel lines aat the same time. That way your all set in case the carb needs rebuilt also?
 
Sounds like you are running this outside the boat. Try raising up the fuel tank to where it would be in the boat, as opposed to sitting on the ground. These fuel pumps can struggle moving fuel up the elevation of the entire motor. It never has this much elevation to fight against when on the water.
 
Just for reference never run any two stroke past high idle out of the water or in neutral. You can easily throw a connecting rod if it runs away on you.
 
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