Outboard motor
Submitted: Sunday, Mar 10, 2013 at 16:53
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Shaun T
Hi all I have a 40hp Toshatsu outboard and it has a miss fire in the in the number one piston, it keeps fowling the spark plug ( they are brand new plugs and has fresh fuel ) so if anyone my be able to help me out that would be great thanks
Reply By: Roughasguts - Sunday, Mar 10, 2013 at 19:17
Sunday, Mar 10, 2013 at 19:17
Hmmmmm might be starving fuel! is that motor oil injected? might be getting the oil but no fuel that equals bad!!!! could lean out and melt a piston.
Is top cylinder hot to touch EG: cant hold your finger on it? 7 seconds before you have to lift your finger is rule of thumb so to speak if engine to Hot.
Thinking it may be a clogged main jet E10 will do that to a needle and
seat and maybe even a main jet.
Drop the drain plug from the top carby and pump the fuel bulb see how much fuel comes out. Should flow out easy when you pump but if it doesnt say have 30-40 ml of fuel in it to start with say the float bowl could be the problem not letting enough fuel in.
Cheers
AnswerID:
506513
Follow Up By: Ross M - Monday, Mar 11, 2013 at 22:44
Monday, Mar 11, 2013 at 22:44
More likely a blocked emulsion tube which causes the richness and fouling and therefore a misfire.
The fact it runs up on full accelerating throttle which uses richness to produce the power but it is no good when backed off.
So main jet can't be at fault, but the fine holes in the emulsion tube can be blocked.
Petrol gumming.
No good using E10 in an outboard as it lowers the energy density of the fuel and effectively will run leaner. Less power needs more throttle to turn the screw, so no gain there.
The float bowl must be allowing enough fuel in as it runs high revs and it can't do that if staved by not letting enough. Exact opposite.
Ross M
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