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Old 18 June 2007, 15:14   #1
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Country: UK - England
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Boat name: Johanna Maria
Make: Sacs Jamaica
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Engine: Tohatsu,Petrol,120hp
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Tohatsu 120 - Full Throtle Problem

Hi everyone

I have a tohatsu 120 petrol on a Sacs Jamaica speedboat 5.3m. I am experiencing some probems with the full throtle. Once I start the engine and I am out of the harbour I press the full throtle but the engine refuses to listen. It reaches the full speed after about 30 secs. Sometimes I have to pause it to take the throtle back down completely and start it again in order for the engine to react. Does anyone have any idea what could possibly go wrong?

Thanks in anticipation

Nikos
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Old 07 August 2007, 16:38   #2
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Quote:
Originally Posted by jneadt View Post
Hi everyone

I have a tohatsu 120 petrol on a Sacs Jamaica speedboat 5.3m. I am experiencing some probems with the full throtle. Once I start the engine and I am out of the harbour I press the full throtle but the engine refuses to listen. It reaches the full speed after about 30 secs. Sometimes I have to pause it to take the throtle back down completely and start it again in order for the engine to react. Does anyone have any idea what could possibly go wrong?

Thanks in anticipation

Nikos
Hi there, sounds like lack of fuel to me, check that the tank vent is open, check your fuel line connection's for leak's that might be taking air in, check fuel flow, drian your carb's checking for water, if all these are ok then strip and clean the carb's, probily one of the main jet's are bloked, hope this help's. Chris.
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Old 07 August 2007, 16:51   #3
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I reckon it's the opposite - too much fuel causing the engine to bog down. Could also be the plugs or both.
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Old 07 August 2007, 17:25   #4
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I had a similar problem on my twatsoo 70.

It turned out to be the plastic conections on the throttle linkages that had partially jumped off.

the symptoms were that it would rev to aprox 4K rpm normally and then the motor felt like it was "searching" for fuel when trying to go faster. In this case I recon that at full throttle the timing advancer arm would have been at its max position but the carbs would have been only 2/3rds open because the plastic links were not in the correct position. (does that make sense?)

It was an easy fix though, I just cliped em pack on and then I wrapped some fuse wire around em so it wouldn't happen again.

Im not sure if this is of any use to you but it is worth a quick check.
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Old 08 August 2007, 05:39   #5
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Too much / too little fuel.....

First check your fuel supply for leaks or restrictions. If you're happy that enough motion lotion is getting to the carbs, then a simple way to test your fuel / air mix without dismantling or adjusting anything is as you arrive at the point where it starts to die, prod your choke button - if it takes off like the proverbial scalded cat, you are running lean (i.e. not enough fuel). if it coghs & dies, you have too much fuel in there.

Theory here is that a momentary moment of choking will add a "lump" of fuel to the mix, upsetting the balance for better or worse.

.....Then you have the fun of finding out why it's running too rich or lean!
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