Tohatsu M50D2 Fuel System

cleve

Petty Officer 2nd Class
Joined
Sep 18, 2008
Messages
156
Long story short...
Owned this boat/motor (1999 50hp 2 stroke) for 8 years, sold it to buddy (regretted it), and bought it back from him a few months ago. He used it an average amount, but hadn't done any service to it in the 3 years he had it.

Put fresh gas in and took it out and it started up fine, but wouldn't run over @4500 rpms like starved for fuel (no alarms). Was alone so hard to play with the choke and bulb while running, but pumping bulb then going back to seat, it did try to briefly rev higher. It had done this with me several years ago and it was clogged high speed jets. Removed carbs and sure enough jets were clogged, but the carbs overall weren't bad at all, hardly any varnish and floats appeared to be in good shape. I did not do a soak or change any gaskets/o-rings (good shape) and cleaned with carb cleaner and air. Also, cleaned the fuel filter but didn't think to look at the fuel pump. Did not water test, but on muffs it still doesn't run right and now it won't idle without throttle slightly raised. The fuel hose and connectors were corroded so I plan to replace those and the tank. Any advice? Should I replace fuel pump too and do a more thorough carb cleaning? I also went ahead and replaced impeller, spark plugs, and gear oil while I was at it.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Was the motor kind of missing, hesitating when running over 4500 rpm ? When fuel connector o'rings at both sides becomes dried, hardened with use will let air in the hose and motor will start to miss. Those o'rings are not available as spares, remove both with a thin needle and take them to a auto parts store and have them measured will save money if plan keeping the old fuel hose and their side connectors as well.

If fuel pump is suspect, remove it and have a look at the internal diaphragms condition to check if cracked, warped, if so replace for new spare parts..

Happy Boating
 
Last edited:

cleve

Petty Officer 2nd Class
Joined
Sep 18, 2008
Messages
156
Was the motor kind of missing, hesitating when running over 4500 rpm ? When fuel connector o'rings at both sides becomes dried, hardened with use will let air in the hose and motor will start to miss. Those o'rings are not available as spares, remove both with a thin needle and take them to a auto parts store and have them measured will save money if plan keeping the old fuel hose and their side connectors as well.

If fuel pump is suspect, remove it and have a look at the internal diaphragms condition to check if cracked, warped, if so replace for new spare parts..

Happy Boating

I bought a new engine side OEM Tohatsu connector (male and female), new hose, and a new tank. The current tank is an older OMC duratank and it's leaking fuel around the manifold.
Plan to connect all in next few days, put fresh gas in, and see how it runs. If it still runs rough, may have to take carbs back off and take a look at the fuel pump while doing so.
It didn't really miss or hesitate at 4500, but it did surge a few times.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Test new fuel hose and tank, hope all goes well...

Happy Boating
 
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