Been working on a '77 75hp Johnson motor.
Its hard to start, when I can get it to run it will idle for a while, then slowly drop RPMs til it dies. Almost like it is flooding out. When I take it on the river, its even worse. Sometimes it will die and not restart at all. When I get it to run enough to take it out, about 4,300rpm is all it will handle. And that's at 3/4 throttle. When at full throttle it almost seems like its pegging off the rev limiter.
First checked compression and all three are even at 95psi; a little low, but even. Did a leak down test, with 0 - 10% leak on all cylinders; there again, even. I did the link/sync procedure, making sure my throttle isn't opening too far. The timer base tested bad so I have replaced that, along with the power pack. I cleaned the carbs, rebuilt the fuel pump, and even tried new reeds with no improvement. The last thing I did was pull the head to visually inspect the cylinders, which all were fine, no scoring. The one thing I did find in the cylinders was a brown, thick oil like substance similar to unburnt oil. The motor isn't overheating or anything like that, running a nice temperature.
I am at a complete loss on this one, anything anybody has in mind will help.
Thanks
Its hard to start, when I can get it to run it will idle for a while, then slowly drop RPMs til it dies. Almost like it is flooding out. When I take it on the river, its even worse. Sometimes it will die and not restart at all. When I get it to run enough to take it out, about 4,300rpm is all it will handle. And that's at 3/4 throttle. When at full throttle it almost seems like its pegging off the rev limiter.
First checked compression and all three are even at 95psi; a little low, but even. Did a leak down test, with 0 - 10% leak on all cylinders; there again, even. I did the link/sync procedure, making sure my throttle isn't opening too far. The timer base tested bad so I have replaced that, along with the power pack. I cleaned the carbs, rebuilt the fuel pump, and even tried new reeds with no improvement. The last thing I did was pull the head to visually inspect the cylinders, which all were fine, no scoring. The one thing I did find in the cylinders was a brown, thick oil like substance similar to unburnt oil. The motor isn't overheating or anything like that, running a nice temperature.
I am at a complete loss on this one, anything anybody has in mind will help.
Thanks