50 hp Yamaha choke???

[borz170]

A customer brought me an engine this summer after just purchasing it. We checked compression, 118 psi and cleaned carbs. Test ran it and it ran like a yami should, great.

He brought it back 3 months later with problems. In the driveway, it would miss at idle and continue to miss if we reved it up then idled. Cleaned carbs which were not dirty, checked fuel water seperator (clean), fuel was not restricted from junk in the tank because it siphoned easily, changed spark plugs that were fouled, then tested it. It ran like crap, you could not get it to plane. It acted like it was starving for fuel.

Replaced fuel pump with no success.

We then noticed that the choke was in the on position rather than the off position like it should be. We checked compression again and it was the same. New spark plugs and same problems. We have determined it is getting enough fuel, it seems to be fouling spark plugs very quickly. Now, we can get it to plane out if someone is constantly adjusting the electric choke on the motor.

We tore the choke apart and cleaned it with no success. At this point the guy wanted his boat back, so unfortunately I had to turn over a boat that I could not fix or charge for. I have a ton of hours in this boat and still no answers. Has anyone else ever had a similar problem?

 

[littlejohn2458]

Re: 50 hp Yamaha choke???

what year is that motor? If its a 2000 or newer make sure that the timing is working right. The throttle position sensor on those motors have given me problems that make it seem fuel related. Also did you check and make sure it was getting spark on all 3 cylinders? if its got the ecm/cdi with the arm on it. check to make sure that the yellow wires on the back are plugged in and not unplugged. (return to port mode)

The timing should move when that throttle position sensor is moved back and forth.

 

[littlejohn2458]

Re: 50 hp Yamaha choke???

also, did you check for leaks in the fuel system. Are all the hoses zip tied tightly and no air leaks? Sometimes the fuel filter on the engine tends to swell a little bit which causes it to leak air when you replace the filter....

Just another thought.

 

[99yam40]

Re: 50 hp Yamaha choke???

A customer brought me an engine this summer after just purchasing it. We checked compression, 118 psi and cleaned carbs. Test ran it and it ran like a yami should, great.

He brought it back 3 months later with problems. In the driveway, it would miss at idle and continue to miss if we reved it up then idled. Cleaned carbs which were not dirty, checked fuel water seperator (clean), fuel was not restricted from junk in the tank because it siphoned easily, changed spark plugs that were fouled, then tested it. It ran like crap, you could not get it to plane. It acted like it was starving for fuel.

Replaced fuel pump with no success.

We then noticed that the choke was in the on position rather than the off position like it should be. We checked compression again and it was the same. New spark plugs and same problems. We have determined it is getting enough fuel, it seems to be fouling spark plugs very quickly. Now, we can get it to plane out if someone is constantly adjusting the electric choke on the motor.

We tore the choke apart and cleaned it with no success. At this point the guy wanted his boat back, so unfortunately I had to turn over a boat that I could not fix or charge for. I have a ton of hours in this boat and still no answers. Has anyone else ever had a similar problem?

Did you test anything on this motor or just start replacing parts?
Surely you have a fuel pressure/vacuum gauge to see if the supply system is doing it's thing and a DVA meter or at least a DVA adapter and regular meter to check the different inputs and outputs of the CDI.
How do you "constantly adjusting the electric choke on the motor"?
If you have to choke a motor to make it run it means the carb has fuel in the bowl, but the passages are plugged and need to be cleaned