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My friend recently bought a second hand Yamaha 40FM 6E9 outboard motor. The person who sold it to him said that the motor was playing up at times and proceeded to show us what was happening i.e.:
1) At low rpms the motor works fine.
2) Upon increasing throttle to half/three quarters way the motor speeds up, only to lose power/bog down and 'shiver' after some 15 or 20 seconds and continue moving forwards at a very slow pace (close to idle), as if not enough fuel was available or not being ignited.
3) Once this happened, we had to reduce throttle and leave it idling for a couple of seconds more before attempting to speed up again, at which point the smae thing happened again.
4) Funny thing was that when we increased throttle to three quarters way and then decreased it to idle, some seconds later the problem re-manifested itself.
5) We also tried playing around with opening and closing the air jets and also connected the fuel directly to the engine (by-passing the filter) to no avail.
Hence we dismantled and cleaned the carburettor, replaced the fuel filter, sparking plugs, fuel lines, gaskets, oil seals, fuel pump with original parts....everything we could think of and assembled everything again.
We also installed an original yamaha fuel tank
....As yet, the problem still persists.
We are now thinking that it could be a problem with the coil???
Any comments/suggestions shall be greatly appreciated.
1) At low rpms the motor works fine.
2) Upon increasing throttle to half/three quarters way the motor speeds up, only to lose power/bog down and 'shiver' after some 15 or 20 seconds and continue moving forwards at a very slow pace (close to idle), as if not enough fuel was available or not being ignited.
3) Once this happened, we had to reduce throttle and leave it idling for a couple of seconds more before attempting to speed up again, at which point the smae thing happened again.
4) Funny thing was that when we increased throttle to three quarters way and then decreased it to idle, some seconds later the problem re-manifested itself.
5) We also tried playing around with opening and closing the air jets and also connected the fuel directly to the engine (by-passing the filter) to no avail.
Hence we dismantled and cleaned the carburettor, replaced the fuel filter, sparking plugs, fuel lines, gaskets, oil seals, fuel pump with original parts....everything we could think of and assembled everything again.
We also installed an original yamaha fuel tank
....As yet, the problem still persists.
We are now thinking that it could be a problem with the coil???
Any comments/suggestions shall be greatly appreciated.
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