"I bought a used boat a few we
"I bought a used boat a few weeks ago with a 2002 Yamaha 150 2-stroke (carb model). The motor has about 250 hours on it, and runs great at cruising speed, but has intermittent idling problems.
It starts fine cold and idles well at the dock, but after running at higher speeds for a while, it won't idle. It idles low and rough (like a cylinder is mis-firing or something), and the exhaust smokes and smells very rich, and then it dies. I can keep it running by cracking the throttle a bit and running a high idle, but it still smells rich.
I changed out the plugs, replaced the water seperator filter and cleaned the fuel strainer on the motor, but it still happens. The wierd thing is that it doesn't always do this. Sometimes it idles fine, other times it smokes and dies.
The boat sat for several months before I bought it, so it may have had some bad gas. I left the old gas in the tank (about 1/4 tank) and filled the remainder with new gas to hopefully "dilute" it enough to be OK.
Opening the choke at idle doesn't help at all, and actually makes it die faster. I thought about cleaning the carbs, but not sure if that makes sense if the choke doesn't help???
Any other ideas - timing, etc?
BTW - the compression was about 100 - 105 on all cylinders and it ran 3250 PSI and 5k RPM on the dyno before I bought it.
Any help would be appreciated..."
"I bought a used boat a few weeks ago with a 2002 Yamaha 150 2-stroke (carb model). The motor has about 250 hours on it, and runs great at cruising speed, but has intermittent idling problems.
It starts fine cold and idles well at the dock, but after running at higher speeds for a while, it won't idle. It idles low and rough (like a cylinder is mis-firing or something), and the exhaust smokes and smells very rich, and then it dies. I can keep it running by cracking the throttle a bit and running a high idle, but it still smells rich.
I changed out the plugs, replaced the water seperator filter and cleaned the fuel strainer on the motor, but it still happens. The wierd thing is that it doesn't always do this. Sometimes it idles fine, other times it smokes and dies.
The boat sat for several months before I bought it, so it may have had some bad gas. I left the old gas in the tank (about 1/4 tank) and filled the remainder with new gas to hopefully "dilute" it enough to be OK.
Opening the choke at idle doesn't help at all, and actually makes it die faster. I thought about cleaning the carbs, but not sure if that makes sense if the choke doesn't help???
Any other ideas - timing, etc?
BTW - the compression was about 100 - 105 on all cylinders and it ran 3250 PSI and 5k RPM on the dyno before I bought it.
Any help would be appreciated..."
