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Mercury Optimax 150 HP - Engine Running very High RPM while in Idle

nourk

New member
This is my first post on this forum and was hoping to get some answers to an issue I have experienced recently:

***Background Story***

About 2 months ago I went to start my Mercury Outboard 150 HP. It would start for about 10 seconds and then cut off. After trying that for about 6-8 times. I decided to give it more gas by pushing on the throttle. The Engine started right up but then when I brought it back to Idle, the RPMs never came down and the engine was running at about 2000 RPMs. Since then I decided not to start it anymore for fear that I would cause further damage. I spoke to the Mercury Dealer and they said that it sounded like a Throttle Position Sensor (TPS) issue. Ordered the Part and my Son helped me change it which was a pretty straight forward process. Unfortunately, that did not do the trick. Now I have an extra TPS as a backup- No Big Deal. Called the Dealer Back, this time they said to check the reed valves and inspect them as they could be letting more airflow into the Crankcase. This Past weekend we took the reed block plate with all 6 reed blocks. Upon inspection, we noticed that the plate Gasket was in pretty bad shape and was leaking Oil (Which we will change) and 5 out of the 6 reed blocks were showing light when we looked through them (as Suggested by the Dealer) . The Dealer also said that it was unusual for that many reed Valves to go bad.

Questions:

1- Has anyone experienced this before?
2- If we put New Reed Valves and the Engine still runs high, any thoughts on what else could be contributing to this behavior?
3- I read on some blogs that the Linkage can also be a culprit

Any suggestions are greatly appreciated.

NK
 
Check the throttle cable first. Maybe disconnect it from the motor and see if it was jammed.

Thanks Mechanicman!

I will check it this weekend and give an update.

I am wondering though, when the Engine is not running and I push and pull back the throttle, I do see linkage moving back and forth. Would that still suggest a cable disconnect or jam you think?

Thanks again,
 
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