2002 F40TLRA Large Amount of Gas in the Crankcase Oil Overflowing When Dipstick Pulld

[bigbeeus]

Here's the sad story...

I have owned this 2002 F40TLRA for over 10 years. Ran fine 5 years ago before I had to park it. Now I am trying to bring it back to new condition.

I have replaced all the carburetor parts with new except the O-Rings. I ultrasonic washed all the carburetor parts. Complete new lower unit service kit. New Oil & plugs. New external fuel tank, water separator, and fuel filter.

Put it in the water and cranked it up and all seemed fine for about 30 minutes and then it started to bog down if you tried to give it gas. Put it back on the big boat and let it sit for 2 weeks. Put it back in the water and tried to start it and it would not turn. Just locked like a cylinder lock. Took it back out of the water and pulled the plugs and the bottom cylinder was full of gas. Pulled the dip stick and fuel and oil came gushing out. I am fairly certain that 2 weeks of sitting with all that pressure in the crankcase was able to force the cylinder full of fuel and oil causing the locked condition.

I saw a video where the fuel pump was pumping gas through the back into the crankcase so I check that. No leaks on my fuel pump and I also took it apart and everything looks and works great there. I did pull the thermostat as some have said and yes I do need a new one but I don't see how that could be causing my problem. Should I pull the carbs and check something there? What am I missing? After only 30 minutes of running it should not have a crankcase full of fuel.

Thanks

[bigbeeus]

2/25/2023 Update:

Figured it out. The accelerator plungers were full of crud. There is so much dirt in the carburetors that they have needed to be cleaned half a dozen times now. Carb cleaner, compressed air, ultrasonic, etc. Lots of little tiny particles seem to come out of no where. I have also replace most fuel lines and another fuel filter. Runs really well now after a link and sync. Still have a problem with getting a low RPM but that I believe is a problem caused by Carb 3 not closing completely setting everything else off a bit. 150 RPM's to high. Still looking for a good carb 3.

[99yam40]

2/25/2023 Update:

Figured it out. The accelerator plungers were full of crud. There is so much dirt in the carburetors that they have needed to be cleaned half a dozen times now. Carb cleaner, compressed air, ultrasonic, etc. Lots of little tiny particles seem to come out of no where. I have also replace most fuel lines and another fuel filter. Runs really well now after a link and sync. Still have a problem with getting a low RPM but that I believe is a problem caused by Carb 3 not closing completely setting everything else off a bit. 150 RPM's to high. Still looking for a good carb 3.

glad to hear you made some head way with this problem.

You need to find out where those tiny particles are coming from.
could it be the fuel lines to the carbs falling apart?
filters should grab most if not all in front of them.

but if you let a motor with carbs sit for long periods of time, the fuel evaperates and leaves residue behind also

[DennisG01]

You should probably completely disassemble the carb... take the jets out, rod the passageways, etc. Ultrasonic is good - but it doesn't always completely do the whole job... especially all the small passageways.

[DennisG01]

but if you let a motor with carbs sit for long periods of time, the fuel evaperates and leaves residue behind also

Especially if a good additive wasn't used. But even then, 5 years is a long time.