more fouled plugs

[bill wright]

i recently installed an electronic ignition system, new spark plug wires, and new plugs. after six weeks the motor ran rough. the two forward plugs looked ok, but the two back plugs were covered with soot. after putting in two new plugs, the motor runs smoothly but i expect that the condition will reoccur. i am told that this is caused by a rich mixture, but why is it only on the back two plugs? how does one adjust for a leaner mixture? oil pressure is constant 40, the spin-on fuel filter never has water but must clean out gunk every couple of months. is a new carburetor indicated? the engine is a "late" model from 1973. has run fine for the previous seven years i've had the boat. thanks for comments

[Don Moyer]

Bill,

In late model raw water cooled engines, the two rear cylinders frequently run a bit cooler due to the fact that the diverter cap directs all the incoming cooling water aft, which has the tendency to overcool the two aft cylinders a bit and cause some sootiness on the two rear plugs.

However, your report strongly suggests that the problem with your two rear cylinders started with the installation of the electronic ignition, plugs and plug wires. This being the case, I'd check to be sure you got the new plug wires on in the correct sequence. You may have the third and fourth cylinders reversed. You might also try changing the second and third plug wires (being sure to keep the sequence the same) to see if the trouble with the third cylinder transfers to the second, indicating a bad plug wire.

As a long shot, if your electronic ignition kit is an Ignitor, you might try removing the magnetic ring on the distributor shaft and rotating it 90 or 180 degrees. If the first and second plugs then become sooty instead of the rear two, it would indicate a defective magnetic ring.

Don

[bill wright]

plugs were Ok, plug wires OK, compression check OK, carburetor OK, leaving only the electronic ignition. Rotated the ring 90 degrees and problem appears solved. Why is there nothing in the instructions which mentions that the ring may be installed incorrectly and may need to be rotated? runs rather smoothly, but will rotate another 90 degrees to see if there is further improvement.

[Don Moyer]

Bill,

From your brief report, I'm not sure what the difficulty is with your ignition system, but there's no right or wrong way to install the magnetic ring of an Ignitor onto the shaft of the distributor.

Don