Engine problems / 2003 V6 150HP Johnson

[Rincon823]

Hi guys!!! I have a 2003 V6 150hp Johnson that is giving me some problems. I was fishing (trolling) and after two hours the RPM’s start increasing without any control. I turn off the engine put it in neutral (idle position) and try to turn it on. During ten seconds the engine works OK but suddenly the RPM’s increased. Somebody have an idea of what the problem could be? (OIS, power pack…)
Thanks in advance.

[boats.net]

It could be an ignition problem, lean fuel condition or air leak somewhere on intake. Check to see if timing is steady, see if pumping primer bulb makes any changes.

[Rincon823]

I checked the fuel and prime bulb and they are good. Regarding the ignition, last year I have to change the "optical timing sensor" because the engine suddently went dead... You think this new condition (increasing RPM) could be related with a damage (intermitent function) of this "timing sensor"?
Thanks!!!

[boats.net]

It is possible, have it tested and look for cracks.

[JUST-IN-TIME]

sounds like air leak to me

[faztbullet]

How many rpms does it gain or does it just keep going? If it goes up to 1200-1500 rpms and stays there it could be a pack going into "quick start" mode or port t-stat is hung open and will not let pack out of "quick start"