Hello,
Last summer, I reported some troubles with my 50 Deto that would not rev more than 4400 rpm. I worked on it this winter to try to find what would cause this.
I checked timing with a timing lamp, checked pulser coils with a scope, and checked sparks with an homemade spark tester. The carbs are clean, and I rechecked them.
I changed the fuel pump in order to be sure to have sufficient fuel supplying and no air sucking in the lower cylinder.
Yesterday, I went to the sea for a test drive. The motor started fine, and after idling a while to leave the dock, I tried to push it to WOT.
I was surprised because the boat jumped out of the water, and the motor was just running fine. It reached 5400 rpm, and the boat 33 mph. Both values It was impossible to reach last year. (15' fiberglass V hull with 50 hp motor).
But....
I was happy for only a short time, because after 1 minute, the motor slowed down to 4400 rpm at wot, like before.
I stopped, checked the bulb it was normal, I couldn't pump it more than 1 time.
I restarted the engine, and it wasn't doing as well as before, then suddenly, It jumped out of the water again, and went to WOT at 5400 rpm again.
I cruised for 2 hours, and the motor was going up and down with power and rpm.
So, It's better than last year, but there is obviously a problem, and I don't know what it is.
could it be fuel related ? I was thinking of replacing all the fuel lines to be sure there is no air sucking.
Or could it be a bad CDI or a bad coil causing the loss of a cylinder ? That's what I was suspecting las year, because the lower cylinder plug was too much clean compared to the 2 upper ones.
Any advice from specialists would be appreciated,
Regards,
JP
PS: Yamaha 50 DETO, 3 cylinders, 3 carbs '89, 2 strokes Autolub.
Last summer, I reported some troubles with my 50 Deto that would not rev more than 4400 rpm. I worked on it this winter to try to find what would cause this.
I checked timing with a timing lamp, checked pulser coils with a scope, and checked sparks with an homemade spark tester. The carbs are clean, and I rechecked them.
I changed the fuel pump in order to be sure to have sufficient fuel supplying and no air sucking in the lower cylinder.
Yesterday, I went to the sea for a test drive. The motor started fine, and after idling a while to leave the dock, I tried to push it to WOT.
I was surprised because the boat jumped out of the water, and the motor was just running fine. It reached 5400 rpm, and the boat 33 mph. Both values It was impossible to reach last year. (15' fiberglass V hull with 50 hp motor).
But....
I was happy for only a short time, because after 1 minute, the motor slowed down to 4400 rpm at wot, like before.
I stopped, checked the bulb it was normal, I couldn't pump it more than 1 time.
I restarted the engine, and it wasn't doing as well as before, then suddenly, It jumped out of the water again, and went to WOT at 5400 rpm again.
I cruised for 2 hours, and the motor was going up and down with power and rpm.
So, It's better than last year, but there is obviously a problem, and I don't know what it is.
could it be fuel related ? I was thinking of replacing all the fuel lines to be sure there is no air sucking.
Or could it be a bad CDI or a bad coil causing the loss of a cylinder ? That's what I was suspecting las year, because the lower cylinder plug was too much clean compared to the 2 upper ones.
Any advice from specialists would be appreciated,
Regards,
JP
PS: Yamaha 50 DETO, 3 cylinders, 3 carbs '89, 2 strokes Autolub.
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