15 hp Force 1997 odd idling problem

[pecheux]

Good day. My OB runs great most of the time. Start fist pull, good acceleration, great wot speed. I can let it run idling gears engaged in water barrel for hours without any issue. Problem is when I run it on the river it will idle good for a short while. After I run the motor wot for some short burst and return to trolling idling speed it will run good for 15 to 30 seconds then start missing and stops. If I am fast enough to turn the gas handle it will accelerate and reset to normal idling ... only to start missing again 20 seconds later ... problem will repeat until it seems to flud and becomes hard to start. Prior to taking it to the repair shop I would like to have some connaiseur's opinion regarding if the seems like a fuel or electrical problem. thank you all.

 

[foodfisher]

Check plugs for fouling?

 

[pecheux]

Thank you for your feedback and suggestion. I just took plugs off and they are clean & what seems to me as having the right brownish color and no oil on the fire point. Low hours on them. BUT ... top cylinder plug had drop of oil around it which may indicate it may not have been tight enough. Could that cause my described idling problem after wot operation ? tx

 

[pecheux]

Talked to a local Merc dealer mecanic today re: this odd idling problem. He suggest setting idle speed to higher rpm and did not show any interest on working on this motor to diag the problem ?? Humm ...

 

[pecheux]

Well this retired computer programmer is taking matters in his own hands. LOL Ordered a gas filter and bought a 13-16 key wrench to have better access to lower plug allowing to tightening properly. Need to know if it's got the right plugs ... now installed are NGK BPR 7HS 10 (written enderneat) Can somebody confirm if those are the right spark plugs for this 15 hp Force OB ? Thank you

 

[fishrdan]

Not sure on the plugs (isn't the plug info written inside the cowl/hood)?

When was the last time the fuel pump diaphragm was replaced, or I should say, when was the last time the fuel pump was rebuilt? If the diaphragm is ruptured is could be leaking fuel into the crankcase and making the mixture too rich. This doesn't explain why it will idle in the barrel, but I've seen a lot of people on the forums with ruptured diaphgrams on the small Force OB's

 

[pecheux]

Thank you fishrdan, I am taking notes. First I will give it a test run on the river after I install the new gas line micro filter and the spark plugs have been tightened, and see if problem is still "on" Regards

 

[pecheux]

Fishrdan: Gas pump is the original and never been rebuilt. Ordered a kit today. Dont know if I'll try doing it myself or let my OB mecanic do it. Thank you for your help.

 

[pecheux]

I have replaced the gas pump kit today. Rather tight space for big fingers .. lol. Motor started on first pull, but more testing will be done in barrel tomorow. Just wondered how tight those 3 screws on the pump have to be ???? I did screwed them in pretty tight with rather big screwdriver. Can anyone chime on that and offer recommendations ? Tx