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1999 Merc 115hp motor very tough starting, if at all

D

DMACK1

New member
When 1st running it will run well, from idle to WOT. After it heats up Motor wont run and can only start it when throttle is moved about 3/4 of the way but smokes very bad. It almost sounds like the timing might have jumped. New plugs, clean fuel filter. Compression is ok not the best. The acceleration pump was just replaced (not the fuel pump). The coils are about 5 years old.
 
I did a compression check yesterday and got 1st cylinder 107PSI, 2nd cylinder 105PSI, 3rd cylinder 101PSI, 4th cylinder 101PSI.
 
Service manual for these engines says below 120# you could expect to have problems. You list no history and starting from scratch is a lengthy process. Your compression numbers are a big negative. Otherwise you have to separate it into starting circuit....spinning the engine fast enough to generate enough spark to fire the plugs, ignition problems, or fuel.

Your comment about timing jumping may have merit. The linkage has to operate the carb's butterflies in sync with the timing. Timing is around TDC at idle and 20-22 BTDC at WOT. There are numerous plastic gadgets that connect the rods that perform these tasks...those can get worn and/or break. I suggest you get a manual and go through the "Link and Sync" procedure and see where you are then adjust to get where you need to be.

On a temperature associated problem, your stator may need to be replaced as temperature affects the magnetic components needed to generate the triggers, and the stator is a component of the Link and Sync mechanism. At a 20+ year old engine I wouldn't be surprised if you find any of the above problems.
 
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