1979 Mercury 40hp 2 stroke - need some help

[DntBrnDPig]

Hey all - I have 79 Mercury 402 that is leaking fuel. I have rebuilt the carb and replaced the float. I can get it running once I put the boat in the water but once I get to where I am going to fish and shut it off, I have a hard time starting it back up. I have to prime the pump again and give it some throttle in idle. While I am fishing and using my trolling motor - I can see I am leaving a faint trail of oil in the water from the fuel leak.

Again, I have changed out the float, rebuilt the carb, but can still actively see fuel leaking out the throat of the carb. Any ideas? Anyone have a recommendation on where to take this that won't cost me a ton of money around Cleveland?

 

[megalomaniac]

Did you replace the needle and seat when you rebuilt the carb? It sounds like the needle on the float is getting stuck. Fuel lines good?

 

[DomG]

X2 on Floats not shutting-off the fuel supply. I had a 3 cylinder version of that motor for @ 5 years....fond memories.

The leak on my 40HP was the needle-seat and....an ethanol-rotted fuel line.

 

[Iglow]

Hey all - I have 79 Mercury 402 that is leaking fuel. I have rebuilt the carb and replaced the float. I can get it running once I put the boat in the water but once I get to where I am going to fish and shut it off, I have a hard time starting it back up. I have to prime the pump again and give it some throttle in idle. While I am fishing and using my trolling motor - I can see I am leaving a faint trail of oil in the water from the fuel leak.

Again, I have changed out the float, rebuilt the carb, but can still actively see fuel leaking out the throat of the carb. Any ideas? Anyone have a recommendation on where to take this that won't cost me a ton of money around Cleveland?

I had these exact symptoms on a 50's 5hp Johnson . Had to pump the bowl full, it would run it out and quit, pump and go some more. It weeped fuel too.
Hit a log on the Cumberland river in 1980 and that motor has been resting quietly on the bottom since.

 

[Lt.Dan]

One last thing to check is your priming bulb. They often go bad and are a cheap fix.

 

[DntBrnDPig]

Thanks all! I took it apart and put in the new needle and seat. The new needle looks like it has a rubberish tip. When I put it back together I had a leak still but it was a screw plug at the bottom. I got it solved but still having issues.

If I remove the fuel line from the outboard, I can prime to the bulb and it becomes hard/pressurized and holds it. I have been reading online that this may be the fuel pump thats my issue. Not sure how to test it.

 

[Tenntrapper]

Thanks all! I took it apart and put in the new needle and seat. The new needle looks like it has a rubberish tip. When I put it back together I had a leak still but it was a screw plug at the bottom. I got it solved but still having issues.

If I remove the fuel line from the outboard, I can prime to the bulb and it becomes hard/pressurized and holds it. I have been reading online that this may be the fuel pump thats my issue. Not sure how to test it.

What motor is it? Year, make, and HP?

Edit... nevermind. I'm blind as a bat..


Edit...

https://partsvu.com/blogs/boating-resources/how-to-tell-if-your-outboard-fuel-pump-is-bad