1976 850 runs on upper 2 cylinders

B

Bushgopher

Recruit
Joined
Jun 29, 2020
Messages
3
I have 1976 mercury 850 that's only running on the top 2 cylinders. Lower 2 have spark and all cylinders have 145 psi for compression. I've tried cleaning the carbs twice now but nothing I have done will fix the issue. Removed the power head and started tearing it down. Just as I was going to remove the lower crank housing/intake I noticed there are 2 fittings with a like a crossover hose that goes into the reed block area. On the lower fitting there is also a tiny little hose barb that had no hose on it. Not sure what hose is supposed to go onto this little barb or where it even is. So since this hose is missing is that my problem why the lower 2 cylinders aren't firing? Because its getting the wrong air mixture into the cylinders, or even that it's getting too much air through there because when the engine is running you can watch the fuel come up out of the main jet but it pools in the intake and isn't getting sucked into the engine. Also since I have the intake off, all of the reed valves look to be in good shape. Now since I've got it apart im gonna probably install new reeds, rings, and bearings. So I guess what I'm asking is what hose goes onto that hose barb or is it supposed to be plugged?20201104_115818.jpg
 
C

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,524
There should be a small diameter hose from the lower main bearing to the upper main bearing. You should install it if it is missing. I doubt that is your issue though.

You might check the lower cylinders for water infiltration. You should see beads of water on a rag when cranking it with the plugs out and the flusher attached. Also the spark plugs will be real clean.
 
You must log in or register to reply here.
Top