Merc 4-cycle stalling, shutting off, misfiring at WOT. It was the TPS.
Posted: Mon Jun 05, 2023 11:26 am
Okay I have been chasing an super annoying issue on my Merc 90HP 4-cycle for years now, and I wanted to pass along the fix for me.
I saw the following symptoms:
-Randomly hard to start, cold or warm
-Randomly turning off when throttling down to neutral from WOT
-Random powerful and jarring misfires when at WOT
Its hard to diagnose things without the official Mercury scanner, and also when you dont have quick easy access to your boat. But all the pieces started to point to the position of the throttle lever, so I decide to take a chance and replace the throttle position sensor (TPS). So I have had two long days at the lake since replacing it, and there has not been the slightest single hiccup with the motor...Woohoo! I am feeling very good that this issue is now resolved. BTW, the TPS can be replaced in less than five minutes with a basic Torx driver and a can of beer.
Finally and for good luck, I gladly chucked that thing from the bow and sent it to the abyss of my local lake. Good riddance. LOL.
Keep on boating guys.
Bill
I saw the following symptoms:
-Randomly hard to start, cold or warm
-Randomly turning off when throttling down to neutral from WOT
-Random powerful and jarring misfires when at WOT
Its hard to diagnose things without the official Mercury scanner, and also when you dont have quick easy access to your boat. But all the pieces started to point to the position of the throttle lever, so I decide to take a chance and replace the throttle position sensor (TPS). So I have had two long days at the lake since replacing it, and there has not been the slightest single hiccup with the motor...Woohoo! I am feeling very good that this issue is now resolved. BTW, the TPS can be replaced in less than five minutes with a basic Torx driver and a can of beer.
Finally and for good luck, I gladly chucked that thing from the bow and sent it to the abyss of my local lake. Good riddance. LOL.
Keep on boating guys.
Bill