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Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3976
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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I have a 2002 135 HP Optimax which has been very well maintained

Customer Question

I have a 2002 135 HP Optimax which has been very well maintained and serviced. I took it out for the first time 2 weeks ago. It started immediately and ran great for about 40 minutes when I shut if off at a dock and went ashore for about 2 hours for lunch. When I started it back up, the engine revved to about 5300 RPM, very loud and then stalled. I waited about 5 minutes and started it again and again, it revved immediately to about 5300 RPM for a few seconds and then stalled. I got towed, put it on the trailer, flushed the engine, drove it home and brought it to my marine mechanic. He checked it out-no codes in computer, no alarms. The engine started up at the shop with the "ear muffs" and ran beautifully. He said that the fuel pressure was good and he was not able to reproduce the condition and that he had never heard of such a thing before. I took the boat hime and went out on a freshwater lake- started right away and ran for about 20 minutes with no problems at 4000-4500 RPM. I shut it off and drifted while having lunch for maybe 45 minutes. When I restarted the engine, the same thing happened again but after about the 3rd time it over-revved, I was unable to start it. I did notice that usually when I squeeze the fuel primer bulb 3-4 times, it gets full and firm but this time it did not even after 7-8 pumps. . I had 3/4 tank of stabilized gasoline. I brought it back to my mechanic and again, in the shop with the earmuffs on, the engine ran beautifully and he could not find any problem. Tomorrow, he will take it to the lake and run it to see if he can reproduce the problem.
Is this a tracker valve problem? I have found some blogs where they talk about the same symptoms- over-revving on idle and stalling because of a tear in the diaphragm.
Submitted: 2 years ago.
Category: Boat
Expert:  Charles replied 2 years ago.
Hello, This is Charles, thank you for requesting me today. This could be an issue with the tracker valve. But it could also be an issue with the pulse pump. If either diaphragm was torn the engine would be getting too much fuel and could over rev. Are they going to look at it tomorrow?
Customer: replied 2 years ago.
He is going to take it out on the lake to see if he can reproduce the condition. He has not mentioned the tracker valve or pulse pump but I am planning to call there tomorrow and mention it to him.
Expert:  Charles replied 2 years ago.
You could also have the throttle cable out of the bracket, and hanging sometimes.
Customer: replied 2 years ago.
I am not sure but I think he checked that because it is a fairly obvious possibility but I will ask him tomorrow. Thanks.
Expert:  Charles replied 2 years ago.
Some times it is the really simple stuff that is overlooked?
Customer: replied 2 years ago.
I came across a fuel delivery diagram for the optimax last night and I noticed a check valve on a hose that went from the fuel rail back to the VST. Considering that the fuel injected by the injectors is determined by the fuel rail pressure, the aperture size of the injector and the amount time that the computer holds the injector open, could an intermittently sticking check valve lead to a high fuel rail pressure and deliver an inappropriate amount of fuel causing it to race and then stall?
Expert:  Charles replied 2 years ago.
A pressure regulator failure would cause this along along with a failed air regulator.