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Tohatsu 30hp miss firing

J

jerson

New member
I'm hoping to pick some brains. I have a 2000 30hp Tohatsu, when i start it at the boat ramp it runs fine, when i'm under way & the motor warms up, usually about 500M, it starts to miss fire at speed. I then throttle back & it run ok for a while, then the miss fire begins. This is the case until it's just moving at idle in gear. I'm thinking it may be a problem with the spark plug leads. Both these leads run to a ignition coil assembly.

I also have a problem with the electric start, it begins to turn over then just clips. It starts fine with the pull start, could both these problems be related.

Thank you in advance.
Jerson.​
 
Assuming you have an M30A4 2-cylinder 2-stroke. (You didn't say, and year means nothing for servicing a Tohatsu). Could be any number of things; Fuel systems are the most common problems today, but thermal problems in the ignition are not unheard of.

Have you checked/gapped the plugs? What plugs are you running? Have you tested the ignition components? Have you tested the fuel system? Is the telltale flowing properly? If not, grab your trusty FSM, and see what is what.
 
Paul,
Yes it is a M30A4.
Plugs replaced with NGK BR7HS.
I haven't checked the plug gaps.
The motor runs fine in a drum of water at a fast idle, out of gear, for 1/2 hour.
Tell tale works fine & doesn't look to be spraying water on electrics.
Fuel filter is clean, lines in good condition.
I don't know how to test the ignition componets.
Can you tell me what my trusty FSM is so i can grab it!!!!!

Many thanks Jerson.
 
racerone said:
An ----------fsm-------might refer to a Factory service manual.
Click to expand...
Yep. Available from any dealer... even me.
When was the last time the carb was properly cleaned?
Running in a barrel is not the same loading that you get on the boat, so it isn't a really good approximation of running under load. In gear under load, you require a lot more power, which means correct fuel mixtures and flows. Can't really duplicate that, even in a test tank.
 
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