Merc 850 timing

[buddyp]

Do I NEED TO CHANGE THE TIMING ON MY 1975 MERC 85 4CYL? THE MANUAL SEZ 27 DEGREES AT WOT. I HAVE HEARD THAT THE INLINE MERCS BURN PISTONS IF NOT BACKED OFF TIMING?

 

[emckelvy]

Re: Merc 850 timing

This is true, the factory did come out with a recommendation to back the timing off a few degrees. 24 deg BTDC oughta do the trick.

BTW if you have "back-drag" style carbs with a brass-colored 'vent jet' at the top of the float bowl, you should remove the jets from both carbs. And plug with a BB the little black hose that runs from the carb throat to the float bowl cover.

Back Drag carbs were designed to lean out the mixture at mid-range for better economy, with today's fuels that's a recipe for burnt pistons!

Check here for a writeup on the Link 'n Synch procedure:

http://forums.iboats.com/showthread.php?t=168855

Note the 21 deg BTDC spec is for Inline Sixes, your I-4 is good at the higher 24 deg spec.

HTH.........ed

 

[buddyp]

Re: Merc 850 timing

Thanks for the good info..you guys are the best! Another question..is there a web site that I can find merc manual info?