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Mercury Model 75 7.5hp starting/timing issues

T

T and J Racing

New member
I consider myself reasonably able with tools and have rebuilt many 2 stroke bike motors, though never an outboard. I picked up this one not running and have had the same issue since buying it.
Here's what I've done:
  • Rebuilt water pump
  • New correct plugs
  • split cases and installed new crank seals
  • ultrasonic cleaned, inspected and reassembled carb

It only starts when I manually advance the timing all the way. It cuts out immediately when I try to return timing to the "start" or "idle" positions. I have cleaned, inspected and reassembled the throttle/timing linkage several times, but I don't see where it's even possible to adjust it.
Here's a shot of the throttle/timing linkage under the flywheel. Considering how clean it looks, I really feel like I'm overlooking something simple. Any suggestions?


 
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The 1976 does not have a primary pickup adjustment what issues are you having? My book shows a max timing at 35 BTDC. With the engine off shift into forward gear and take it WOT and the throttle butterfly should be close to level?
 
kimcrwbr1 said:
The 1976 does not have a primary pickup adjustment what issues are you having? My book shows a max timing at 35 BTDC. With the engine off shift into forward gear and take it WOT and the throttle butterfly should be close to level?
Click to expand...

Yes, at WOT the throttle butterfly is pretty much fully open and the primary pickup appears to be fully advanced. The only way I can get it to start and run is to remove the throttle lever and advance the primary pickup to the WOT position. It will cut out and die immediately as soon as I try to return the pickup to the "start" or "shift" positions.
 
Re: spark tester, no I used the old-school method of grounding the plug and pulling the motor over, looking for a bright blue spark. Plus it runs when the ignition is advanced, that seems to indicate the coils are functioning, right?
Jeff, what looks wrong to you?
 
It must jump a open air gap of at least 3/8 inch brite blue snap your test was useless to us. You can stick a screwdriver in the plug wire and hold the shank 3/8 from a good ground as someonepulls the rope. Im assumingyou did a compression test also you need 110psi plus onboth cylinders.
 
..."Jeff, what looks wrong to you? "

Nothing in the photo. It's almost like the trigger coil magnets are off a bunch of degrees.

Jeff
 
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