Anyone have problems with a crankshaft position sensor ?

S

SEA3PO

New member
I have a Yamaha F40 4 stroke carbureted outboard 2003...It has never run properly...ever.. it is hard to start and does not like to come up to speed...often just dies..

I have tried changing every part I can think of....(switching parts from my other engine) nothing works...Could it be the Crankshaft Position Sensor ? Any idea's that I have missed....this engine has always been a pill...from new...I have rebuilt the carburetors at least 6 times.

Joel
SEA3PO
 
The crank positioning senser is part of the fuel and spark mapping for the engine it could very well be the problem or at least part of the problem. Without the proper diagnostic tools other than switching units I cannot tell you how to test yours
 
If you're running twin motors and the crank position sensor is not too hard to access, I would swap the sensors and see if the problem follows the sensors. No cost other than your time. Also inspect the wiring and connectors .
 
I had a yamaha 90 that had the throttle position sensor adjusted incorrectly. It was on the arm that actuated the throttles — it deals with controlling timing. When it was wrong, the motor started poorly. I would check and see if your motors have them and if they are adjusted the same. (In looking at parts guides, I do not see them on the F40). They are easy to see and adjust. Ron
 
My carbed f90 has an electronic switch on the throttle control linkage — I believe it affected the timing at various throttle settings, thus a position sensor. It did not have a mass airflow sensor that is on fuel injected motors, but it did have a throttle position sensor. It can be seen on a parts blowup on boats.net for a 2003 F90 Yamaha.
 
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