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200 EFI 1997/1998 motor speed fluctuates.

W

Willem

New member
My boat Speed fluctuates between 30 and 35kph wen throttle stays in same place. Makes pulling a skier very difficult. What is causing this and is there anything I can do to sort this out or can i say change the prop pitch from 19 to 17 to move the speed away from ski speed?
 
Might be a fuel delivery issue or old/dirty fuel. Ever change the fuel filters? Dump out the fuel/water separator into a jar to see what is in it.
 
Thank you for the reply. The fuel is good. The problem is only at the speed between 30 and 35 KPH when running faster or slower the motor sings perfectly. I have heard from a guy who raced boats in his life that it is a normal thing on 2 stroke motors something about going over from 2 to 4 valves not sure if I am quoting him correctly. If that is the case is there anything I can do to move this changeover to happen at a different speed?
 
I do not have the exact RPM but it is someting like when I reach 3500 rpm without moving the throttle the rpm drop to 3000 rpm then back to 3500 rpm this keeps going up and down until I push the throttle forward to reach say 4000 rpm then the motor runs constant at 4000rpm. I will have to check the exact ranges though.
 
You didn't provide a serial number. I think there is a "fuel management" problem. The throttle position sensor PN 14851004 may be failing. It is a potentiometer (variable resistor) that can form a bad spot which causes the RPMs oscillation. Pull off the wiring connector and check it. A loose connection can also cause it. Before replacing it--$500 part--have a merc. technician verify the problem. It will be worth the money. JMWAG.
 
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