1976 Merc 850 85HP Maxes Out at 3000RPM

[CharlieB]

Re: 1976 Merc 850 85HP Maxes Out at 3000RPM

Physical swap coils 1 & 2 with 3 & 4 to test and see if the problems switch positions.

Just yesterday I found a dead cyl on a V6, turned out to be a poor connection between the plug wire and the coil.

Hopefully you may be just as fortunate.

Oh, and your model should have plug-in wires, not like I previously thought(Hey I can still brain fart).

 

[crowbuttedweller]

Re: 1976 Merc 850 85HP Maxes Out at 3000RPM

Will try the coil swap tomorrow.

I just finished putting new plug wires, rebuilding the harness and replacing any wire that even looked like it might go bad this century.

Started up and ran just the same.

I had spark on all four just a couple weeks ago. I was getting ready to take it out, put the cover and everything back on and started it up with the muffs just to check spark again and I was back to just 3 and 4. I assumed it was a short somewhere, thus replacing every wire.

Will try the coil swap tomorrow and post the results.

Thanks for all of your assistance CharlieB.

 

[crowbuttedweller]

Re: 1976 Merc 850 85HP Maxes Out at 3000RPM

Swapped the coils.

Switched 1&2 with 3&4.

The problem remains the same. No fire on 1 or 2.

Is it possible this is a grounding problem?

What is the purpose of running the grounds all of the way over the top of the powerhead to the switch box and then grounding to the block?

 

[crowbuttedweller]

Re: 1976 Merc 850 85HP Maxes Out at 3000RPM

Just replaced all of the ground wires from switch box to coils and no change.

Stator and trigger ohm tested again. Still in range.

Can I do voltage tests while running and check the switch box?

 

[crowbuttedweller]

Re: 1976 Merc 850 85HP Maxes Out at 3000RPM

What's my next step? Switch Box?

 

[crowbuttedweller]

Re: 1976 Merc 850 85HP Maxes Out at 3000RPM

I am getting ready to order a new switchbox.

From the photos I see some boxes that have the blcak ground coming out of the box and some that have no wire.


Why the difference? Do I need to make sure the wire is there before ordering?