1986 mercruiser 140 tuning

[bid2ask]

running rough at idle @750 rpm, so i got the tune up parts, points set at 30* dwell, new plugs set gap @35, new rotor, new fuel filter in pump, cleaned filter at carb, new wires, and still runs rough. i decided to look at the timing and it was way of the scale, so i hooked a vaccum gauge to the intake and turned the distributer till i got the highest vaccum, it went to 21 inches, i backed it of to 20 and the idle smoothed out alot, then i looked at the balancer with the timing light and the mark is not even on the scale, its way off the scale.any ideas or should i just run the engine like it is? seems to run good now on the muffs.

 

[Haut Medoc]

Re: 1986 mercruiser 140 tuning

Way off the scale? How much? Being too fer advanced will cause detonation and ruin your engine! Is your distributer in the right position?

 

[bid2ask]

Re: 1986 mercruiser 140 tuning

ok i took all the spark plugs out and turned the engine over by hand till thw #1 piston was at tdc, i got the timing mark lined up perfect with tdc, i took the cap off and the rotor is pointing to the #1 wire...Now what should i do next?

 

[Mahoney]

Re: 1986 mercruiser 140 tuning

as long as you have the dist cap off checking things, check the mechanical advance mechanism in the distributor and clean it. How does it look, all rusty? Broken Spring? Broken spring would definitely lead to a timing mark jumping advancing very far even at idle or a bit above.