1973 mercury 850 won't run

Hello, I have a 73, Mercury 850, a friend of mine installed rings and bearings. The motor has good compression on all 4 cylinders about 130 psi. The motor starts right up and idles fine (in the garage), but when I get it out on the water it won't rev up and go. It acts like it wants to when I first open up the throttle but it dies down fast and just goes slow. I can rev it up using the fast idle control, but it won't rev up with the throttle control. I replaced fuel pump, hoses, plugs and wires. Now I don't know what else to try!

Re: 1973 mercury 850 won't run

sounds like you need a timing and sinc performed, carbs need adjusted in the water ( you can just leave on trailer) very important steps to follow and then your engine should run like it was designed to, it can all be found on these very very helpful two pages

http://forums.iboats.com/forumdisplay.php?f=31&order=desc

Re: 1973 mercury 850 won't run

I had the exact same issue with my motor and turned out to be the power pack was bad and was only running on 3 cyl. Sounded great out of the water but just wouldnt go...hope this points you in a good direction.

Re: 1973 mercury 850 won't run

Inshore, A '73 Merc 850 has a distributor and single switchbox and coil. The only way spark won't get to a plug, is if the plug wire is arcing.

Just, Check the idle pickup timing. The motor should be at 4-6* BTDC when the carbs just start to open. Max spark timing is 21*BTDC, not what the decal says. if the spark timing is OK, richen the top carb idle mixture and see if it runs better. Repeat with the lower carb idle mixture. The idle mixture needs to be a bit rich in order to accelerate smoothly. If you cannot get it to run well, clean and rebuild the carbs.

Re: 1973 mercury 850 won't run

I want to Thank Everyone for their quick replys, I'll let you know how I make out with my problem.

Re: 1973 mercury 850 won't run

Oops I was thinking it was an outboard motor. See thats why im just a little cadet! Just say shut up lol

Re: 1973 mercury 850 won't run

Inshore, That motor is an outboard. Mercs from the 60s and 70s had distributor based ignitions. The change over from distributor ignitions to ADI ignitions was completed on the inline 6 engines in the 1979 model year. Inline fours changed over a year or two earlier.

Re: 1973 mercury 850 won't run

Chris1956, I'm buy no means a outbaord mechanic,but I did try to set the timing, I did it like I used to do the old cars. I put my timing light on the #1 cylinder and started the motor. While idling it was about 6 degrees btdc. When I reved it up the timing advanced to about 22 degrees. It sounded good in the garage and I put it in the water to set the carbs but had no luck. There is a plate ontop the distributor that has a stop on it, looks like it might move a lever that controls the flaps in the carb throat. This has some play in it and I don't believe these flaps are all the way open on full throttle. Could this be a problem? Hope I explained myself well enough. THANKS