mercury 15hp 2 stroke, quits after about 30-60 min of use, then hard to start

[windswepttom]

I had a previous problem that it would only run on one cylinder which I fixed with a new coil. It ran great for about 1 hour and then it started cutting out and only run at 1/2 speed, then for about 5 sec it ran at full speed. This went on for about 20 min, then it ran great.

I thought bad fuel, so I went into a marina and they dumped the fuel, and I put in all new fuel and oil. Started on first pull, ran great for about 45 min, then cutout and quit. It was hard to start.

I let it sit for a few hours and it started on first full. Ran great for about 45 min, then cutout and quit. It was hard to start. So, I readjusted the low speed jet. Ran great for about 30 min, then cutout and quit. It was hard to start. Let it sit for a few hours and starts on first pull. Repeated a few more times.

Each time the fuel bowl/filter was full and squeeze bulb was hard.

Prior to this I:
1. Rebuilt the carburetor
2. Put in new switch box
3. put in new coil
4. put in new fuel
5. put in new spark plugs

It is like something heats up and then shorts out?? How would I test for this?

Can someone give the the resistance readings for the stator wires? My serial number is OG553602.

Any ideas?

Thanks
Tom

 

[flyingscott]

http://www.cdielectronics.com/ will have the test procedures. Try testing spark when the motor shuts down

 

[windswepttom]

Thanks for it idea. OK if I don't have spark when the motor shuts down, how does tell me what part the has the problem other then ignition system?

I did a ohms test of the stator and I think it is OK when cold.
Black/white to ground 166 ohms
Black/yellow to ground 3.76K ohms
Black/white to black/yellow 3.75K ohms

 

[flyingscott]

It will tell you if it's an electrical problem. If you don't have spark run all your tests on the hot components. What kind of gas tank are you running it on? What is the temp of the motor? Is the vent open on the tank.

 

[windswepttom]

Gas tank is just your standard 6 gal red plastic tank with a vent in cap, the motor is not that hot that I can't touch it, the vent is open.
Thanks

 

[windswepttom]

I may have solve it. I replaced the coil/spark plug wires, one of the old ones was tight fit and was laying tight against the head. The new ones are longer and not touching the head. I also replaced the impeller, the old one had 2 broken fins. It now has a stronger stream of water.

I ran it for 90 min in gear at about 1/3 speed tied to the sea wall. Then I shut it off for 30 min and ran it for another 30 min. It ran with no problems.

Thank you Flyingscott for your help

Tom