1987 15hp Evinrude starts but quits every time.

[BigJoe6969]

I’ve had this engine less than a year, it came on a 14’ Armstrong duck boat. Started and ran great in 4 or 5 hunts in the Potomac River, surprisingly easy to start in the cold. Then, I dropped the boat in the Severn (brackish), it started but died when I tried to throttle up. I basically had to run at idle to get out to our spot, but we killed a goose so all good. The next time on the same river I found that if I pumped the ball slowly while at higher RPM the motor wouldn’t die. That worked to get us out to out spot… but we paddled 2 hours home when the motor absolutely refused to stay running. Since then I have gotten fresh gas and new 2 stroke oil, all new fuel lines, new sierra fuel pump, pulled the plugs to check them, and finally completely disassembled and cleaned the carburetor. The result is pretty consistent after all these, it’ll start easily, run for up to 30 seconds, and quit. I can sometimes quickly get it in gear and work the throttle to keep it going a little, but not much.
Any ideas? I really would like to fix this motor.

 

[BigJoe6969]

I’ve had this engine less than a year, it came on a 14’ Armstrong duck boat. Started and ran great in 4 or 5 hunts in the Potomac River, surprisingly easy to start in the cold. Then, I dropped the boat in the Severn (brackish), it started but died when I tried to throttle up. I basically had to run at idle to get out to our spot, but we killed a goose so all good. The next time on the same river I found that if I pumped the ball slowly while at higher RPM the motor wouldn’t die. That worked to get us out to out spot… but we paddled 2 hours home when the motor absolutely refused to stay running. Since then I have gotten fresh gas and new 2 stroke oil, all new fuel lines, new sierra fuel pump, pulled the plugs to check them, and finally completely disassembled and cleaned the carburetor. The result is pretty consistent after all these, it’ll start easily, run for up to 30 seconds, and quit. I can sometimes quickly get it in gear and work the throttle to keep it going a little, but not much.
Any ideas? I really would like to fix this motor.

Can anyone see this? I dont have any responses yet al other posts have many. Why is this?

 

[racerone]

Start with posting compression test values.

 

[Crosbyman]

if it runs 30s it is burning carb fuel and no more

based on " The next time on the same river I found that if I pumped the ball slowly while at higher RPM the motor wouldn’t die"

it sounds like a bad fuel pump or screen. may as well check everything associated with fuel pick-up to fuel delivery in the carb.

 

[brodmann]

Lots of folks here tell us that they cleaned the carb really good. To one guy that meant draining the gas out of the bowls and spraying a can of "gumout" into the drain holes of the carburetors. In order to fully clean that carb, you'll need to get a carb kit and you need to remove some plugs to get to the passages beneath them and they put the plugs in the carb kit back in. If you didn't do that, you haven't cleaned the carb.

 

[Crosbyman]

and a recent case of dirty carb was resolved with several sessions in a ultrasonic parts cleaner at 50C temp. to really loosen crud in tiny passages. see cleaning tools for carbs

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see conclusion on the case mentionned

https://www.aomci.org/forums/topic/1972-evinrude-lightwin-4hp/page/2/e

but do test fuel delivery into the carb.

 

[BigJoe6969]

Thanks. Fuel delivery is good, tested multiple tanks, pulled line off the carb and can see the fuel pump working. Im thinking the float valve must be sticking closed. Does that make sense? Like i pump it up and just enough gas gets to the jet to get it started but then the needle sticks closed and starved it? If it got all the gas is a full carb bowl i imagine it would run for at least a full minute.
But I ordered a carb kit, seems like the obvious next step, i just thought i might not need to as the carb looked clean. And by the way, i sprayed gumout through every little hole
To make sure they were all open. But ill see what happens after rebuilding.

Also @racerone, a little over 100 psi in each cylinder.