Merc 850 won't run below 12 BTDC

[Flossyb20]

Guys - just finished rebuilding the rotating assembly on my 72 850 - I got it fire up today, but it won't run below 12 BTDC, and poorly at that. I checked all the timing events, the carbs were rebuilt, new hoses and fuel pump, fresh gas, all the goodies, but everytime I try to bring it down to 0, it cuts off. Is this a fuel mixture problem? I'm running 25-1 right now, due to the new rotating assembly - compression checks out OK on all, nice blue spark as well. I've also verified the timing pointer is in the correct postition, pretty much everything the manual says to do, I'm at a loss.....

 

[Chris1956]

Re: Merc 850 won't run below 12 BTDC

I would think that 4-6* BTDC should be the idle pickup setting on that motor. It obviously should run at near 0*.

Those older motors had the timing marks on the cowling support. These were unadjustable. Why do you have a timing pointer? Is it original or was it something someone fabricated? I would think that would be the first place to confirm. Did you set the timing pointer at .464" BTDC?