1985 Merc 150. Not going past 3K.

J

James R

Commander
Joined
Feb 1, 2007
Messages
2,664
I have rebuilt this motor so I know it is mechanically sound. This is one of several I have rebuilt down the years.
Idles as it should and picks up well but bogs at around 3k. Tried shooting fuel mist into the intakes while running at bog speed and no change in RPM. That should eliminate fuel as a problem. Throttles go wide open and advance retard seems to be in order. I have been told that the switch boxes have a transition point at about 3K and that although the sparks are real good the boxes may not be performing correctly.
Can anyone help me on this please?
 
j_martin

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: 1985 Merc 150. Not going past 3K.

Stator had a tapped charge coil for each switchbox. Switchbox switches which tap it uses at about 3000 rpm. Could be either one.

The definitive test is to test the stator with a DVA at cranking speed. An ohmmeter test may or may not pinpoint a fault in the stator. Testing parameters are in the manufacturers service manual, and also online at CDI electronics.

On average (odds) it is less expensive to acquire the proper tools and diagnose the problem right, then by one part than it is to guess what the fault is and throw parts at it. Then, after all, you still have the tools for next time.

hope it helps
John
 
J

James R

Commander
Joined
Feb 1, 2007
Messages
2,664
Re: 1985 Merc 150. Not going past 3K.

Thanks John. I don't have the simple C/R with diode to use with my multimeter. Tried to find the parts and ran into availability problems. So without a DVA I am flying blind. The switch boxes had excellent sparks without fault so I doubted that it was switch box. I say doubted because I learned that these motors have stator issues. Fortunately a good friend of mine had a good used stator, a fairly new one. It now resides in the motor I am working on and the Revs come up very nicely now. The lake test will be better proof.
Must get that DVA adapter sorted out.
Thanks again John your help is appreciated.
 
You must log in or register to reply here.
Top