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TOHATSU MFS5B stalling at low speed

G

Guesty

New member
Hello everybody,

I apologize if this issue has already been solved on this forum, don't have the patience to search.:eek: Also, English is not my native language, so don't bash me for poor grammar, etc.;)

Anyway, I bought a used Tohatsu (5 HP, 4-stroke, made in 2010) and when running at the lowest speed possible, the engine slowly dies after about 5-7 seconds. The gear may be in NEUTRAL or FORWARD, doesn't make any difference. Everything's fine if I pull the choke out a little bit, also, the engine runs great at higher speeds. The previous owner sold the engine to a second-hand store without even bothering to remove the fuel from the tank/carburetor and the motor was kept like this for a year or so thus my first idea was "I need to clean the carb". And so I did, thoroughly. Well, the engine starts a lot easier now, but the aforementioned problem remains :confused:. Any ideas?
 
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Yeah, I guess I'll double-clean the carb. Could the problem lie within the fuel pump or filter? Are those difficult to dismantle/clean?
 
Possibly, but not usually. Fuel flow restriction typically affects only high speeds. The filter is a throw-away.
 
I cleaned the carb again (used the remaining spray and dipped the jets and mixing tube into acetone [I've yet to find a proper carb dip, somehow I only come across all kinds of sprays and fuel additives] ) and the fuel pump (which looked absolutely ok IMHO), let everything dry, put it back together, tested the motor, and... same sh*t. :mad: So I gave up on further carb cleaning (unless I find a decent dip) and tinkered with the screw that adjusts how much one of the carb's 'valves':confused: - not sure about the name of the part - is open and made it so that I have the lowest possible revs without the bloody thing stalling. The result isn't that bad, I must say, it looks slow enough for trolling (fishing), so problem solved, I guess. :cool:

Just a couple more questions: what do you use to clean the fuel tank and how do I know that the gear oil needs changing?
 
Carb dip is available in 1-gal. cans at auto parts houses. Acetone alone is not aggressive enough to soften the deposits well. You can use acetone-based generic carb spray to blow out the passages after a 4-hour soak in real carb dip.

The only exposed adjustment screw is the idle stop. That should be adjusted, as per the Factory service manual, with the aid of a good shop tach, after a thorough cleaning.

You can flush loose crud from the tank with gasoline. If it's got sticky or dried crud, a more aggressive solvent may be needed.

As per the owner's manual, change the motor oil and LU lube annually, or every 50 hours, whichever comes first.
 
I may have another problem: I stop my motor at the slowest speed and in NEUTRAL, as indicated in the manual, but when I want to start it again, about 3 times out of 5 the start-in-gear protection kicks in, so I have to put it in FORWARD and then back in NEUTRAL (sometimes it takes a few times) to be able to pull the starter. It's getting annoying. Is something wrong?
 
Guesty said:
I may have another problem: I stop my motor at the slowest speed and in NEUTRAL, as indicated in the manual, but when I want to start it again, about 3 times out of 5 the start-in-gear protection kicks in, so I have to put it in FORWARD and then back in NEUTRAL (sometimes it takes a few times) to be able to pull the starter. It's getting annoying. Is something wrong?
Click to expand...

Sounds like the starter lock needs adjustment. There is a rod that connects to the starter lock cam. That has an angle in it that can be changed so that the starter lock is at its highest point when in N.
 
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