120 running too rich or lean?

[pita482]

Had my boat out today second time after my rebuild on my 1990 120 force thunderbolt ignition, runs great, excellent hole shot, smooth idle and no problems at wot, I ran for about 5hrs today, after I got her home I checked the plugs out of curiosity and they didn't seem as wet as they should and had black carbon around the outside of them (not the middle), it wipes of with a little pressure from my finger,
Could I be running to rich or to much timing? the timing is at 34' static which is 32' and that's was preset when I got the ignition, its a 1990 block with a 93 ignition, the carbs are little more than 1 1/4 out, any input would be great

 

[Jiggz]

If you have carbon build up on the plug tips after only 5 hours of running, there's a good chance you could be running rich. But this all depends on how you ran the motor. Was there a lot of idling or slow speed below 2/3 throttle? If so, yes carbon will easily build up when running slow. Now if most of it is high speed above 2/3 throttle, then you are probably running rich.

I would not do any adjustment for now except maybe back down just a hairline on the carb's fuel air mixture screw.

 

[SkiDad]

i know each engine is a little different but I ran my 1985 125 at 1 turn out - here is my plugs after several week of running - we ran 4500 alot b/c we ski. Do you get a lot of smoke at idle ?

 

[pita482]

Skidad my were very similar to yours down to 1 plug being darker, think I'm a little rich, smokes a little on first start up but the rest of day no smoke, I was pretty much at 5000 throttle, I was prop testing all day, what you run your timing at ?

 

[roscoe]

are you running double oil for breaking after the rebuild?

 

[pita482]

Sorry should of mentioned I'm past the 10 hour break in, so now I'm back to 50:1

 

[jerryjerry05]

Plugs look fine.
​Compression?
​Get it running and warm.
Take cover off and go for a ride.
You'll need someone else to drive.
Get a heat gun and check the temps all over the motor.
Check for hot spots.

​Different temps in different areas can make the plugs carbon differently.

I bought a cheapo gun on line $16
Actually works good.
I don't like dropping expensive stuff overboard. so I buy the cheapo stuff.

 

[SkiDad]

Skidad my were very similar to yours down to 1 plug being darker, think I'm a little rich, smokes a little on first start up but the rest of day no smoke, I was pretty much at 5000 throttle, I was prop testing all day, what you run your timing at ?

i ran my at 32 degree timing which was a little higher than the 30 that most people ran. But I had the prestolite ignition. The plugs in my picture are from bottom to top darkest one was at the bottom.