1974 850 merc compression, fuel, spark and wont run

[bud460]

Any help would be awsome!! I have a 1974 mercury 850 thunderbolt distributor motor. Compression 145# on all 4 cylinders. Rebuilt carbs, replaced fuel pump diaphram, check valves, fuel lines clamps, remote tank with fresh fuel, new timing belt. Good hot battery, good snappy blue spark at plugs, and wont start, wont pop, just spins. Tried small squirt of premix in plug holes and still cant even get a pop! Am I out of time? What timing marks do i line up with distibutor pulley arrow? I used the three vertical dots on the flywheel and when i pull distributor cap with throttle at idle the rotor bug is in between #1 and #3. I tried to set timing so rotor was pointing at #1 when at TDC and still no start, no wanting to start, no pop, but crankin strong and normal?? thanks for anyone who may have some answers, Bud

 

[Chris1956]

Re: 1974 850 merc compression, fuel, spark and wont run

OK, Set the top cylinder to top dead center, using a screwdriver or dial indicator. The timing mark on the cowl support (or the timing pointer, whichever you have) should indicate TDC on the timing decal. If it isn't close, the outer flywheel may be installed incorrectly. If it lines up, the cast arrow on the distributor pullery should point at the punch mark on the flywheel. Adjust the timing belt to make it so.


Adjust the throttle so the carbs are starting to open. Crank her and see what the timing is. It should be 4-6* BTDC. If not, set the timing to 4-6* TDC and loosen the two 5/16" SS bolts on the midsection and move the brass coller with the fingers that open the carbs. Move the collar until it just touches the carbs. the motor should start at this time. Make sure you use enough choke.

After that set the max timing and throttle stop as well as the idle stop screws.

 

[bud460]

Re: 1974 850 merc compression, fuel, spark and wont run

thanks, Im gonna try this again after it stops raining, do you know about where the rotor bug should be pointing at TDC? before #1, on #1, or after #1

 

[Chris1956]

Re: 1974 850 merc compression, fuel, spark and wont run

The rotor should be pointing at #1 or just past #1. It is supposed to fire at 4-6* BTDC.