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Tohatsu M50D2 2003 losing power

E

eciddob

New member
"Engine runs fine up to 3500 r

"Engine runs fine up to 3500 rpm, if I increase the RPM's the engine runs for about 30 seconds the RPM then fluctuates for about 10 seconds and then the engine dies. To restart I have to use the manual choke. I have replaced pump diaphragm and carb needles. Have had it checked out at a dealer and they could find nothing wrong so it appears this only happens when the boat is on the water not when the engine is being being run in a tank."
 
"It sounds like the engine is

"It sounds like the engine is starving for fuel at high RPMs. That could be anything in the fuel system, but it is probably dirty carburetors with a clogged up high speed jets."
 
Our Tohatsu M50D is doing almo

Our Tohatsu M50D is doing almost the same thing as eciddob. It will run all day just fine at about 2/3 throttle but when you try to run it wide open it will only run for a minute & then seems to run out of fuel & die. Have checked & cleaned almost everything. What the heck could the problem be????}}
 
"Just an update. Carbs and fue

"Just an update. Carbs and fuel pump were stripped down twice and cleaned. Fault now occurs over 4200 RPM on the water after running for only 50 to 60 seconds. Tohatsu gave my dealer a special prop that allows the engine to be run in a tank at full load and max RPM without emptying all the water out, this reached 5200 RPM for a considerable time without failing. The fault screams fuel problem but the symptoms are confusing. Will post further if i have any news."
 
"Sounds like a job for:

In

"Sounds like a job for:

In Water Test Man

Tell the dealer to put inline spark checkers on all three cylinders and then run it in the dark, on the water to see if one of the cylinders is loosing spark. Just for the fun of it, also pop off each spark plug wire, one at a time, with the engine running at 3500 RPM and see if the RPM actually jumps up while it is running on two cylinders."
 
"I recently bought a boat with

"I recently bought a boat with the 50hp model d. The engine would do the same thing, as soon as I pass 3500 rpm the boat would lose power, and it had a constant beep untill I put it in neutral for a min I could go again. I took the thermostat out, out and it had corrosion keeping it from moving 25$, and it works with no problem."
 
After no joy with the dealer a

After no joy with the dealer and no one prepared to test it on the water I decided to replaced all the components and lines in the fuel system from the fuel line connector to the carbs. Problem solved. Not the best way to diagnose a fault I know but after such a long running saga drastic action was required. Thanks for the help.
 
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