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Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3875
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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Our Mercury OptiMax outboard engine is giving us a throttle

Customer Question

Our Mercury OptiMax outboard engine is giving us a throttle sensor failure warning light and the engine slows or stalls.
Submitted: 1 year ago.
Category: Boat
Expert:  Charles replied 1 year ago.

Hello, my name is ***** ***** will assist you.

If the engine is doing this mostly at idle, and will go away if you throttle up slightly, it is a bad sensor, and it does require replacement. Some of the early Opti motors were very sensitive to the output of the TPI and would send fault signals the ECU.

Customer: replied 1 year ago.
We stored the boat with 90 gallons of fuel 20 months ago. Could the gas be the culprit. The throttle sensor failure light has been going on intermittently for several years and was simply a nuisance. We were always able to get it going again. But now, it chokes when we go to plane and goes back to idle. This seems to be a new problem.
Customer: replied 1 year ago.
We changed the fuel filter. The old filter appeared to be rusty in color and basically a mess. We changed the spark plugs and added Sea Foam. It went to plane once for about. 45 seconds and got to 35 mph. It has been suggested that we might need new coils. They might be replaced by Mercury as they have had coils fail. Can you find out if the coils would be replaced for free? Mercury OptiMax 150 - 1999.
Expert:  Charles replied 1 year ago.

Based on my experience with Mercury in the shop, they would not replace the coils on your engine due to the age of the engine. The bad coil run was on 2006-2010 engines.

Fuel will not set off the throttle alarm. Only the TPS would.

Customer: replied 1 year ago.
The throttle sensor alarm does not come on every time. Probably less than 10% of the time. Could it be anything else? If the new battery is not strong enough could that cause the inability to sustain plane speed?
Expert:  Charles replied 1 year ago.

Not typically.

Does the warning horn in the boat work still?

Customer: replied 1 year ago.
No we don't have a horn.
Expert:  Charles replied 1 year ago.

Not for the boat, but for the engine.

can you take a pic of your warning light, while pointing at the one that is coming on, and post it here.

Customer: replied 1 year ago.
I told you the warning light does not come on often. Please give other options other than the throttle sensor failure light. I really don't think that's it. Do you think the gas needs to come out? We are replacing a bad coil.
Expert:  Charles replied 1 year ago.

Pat, if you have dumped the fuel filter into a jar, and allowed it to settle. If there is no water on it, there is no need to dump the fuel. the four beep alarms are for a sensor out of range. Low voltage to the ECU, a bad oil rank, water in the fuel, an injector shorted or open, or a temp sensor that is unplugged all can cause it.

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