Merc 2 Barrel Carb tuning

[Boater31]

Its on a 4.3 0L323711. Everything runs great as of winterizing last year. During the winterization and oil change I was getting run-on after turning the key off. I thought maybe it was bad gas as it was getting close to a year old (treated). Well I started it up this year on muffs with fresh gas and it is still running on. It started right up, idles fine though dash tach shows about 800-900rpm but I don't really trust it. It didn't do it at all last year on muffs or water until the last start for oil change. I looked at the throttle cable and it seems to apply positive pressure when at idle. I took the flame arrester off and noticed the choke plate doesn't seem to be open all the way. Looking at the choke the mark line isn't close to the other marks. I tried turning the ignition on but didn't start it and it didn't open any more then shown. This was with a cold engine and not starting it so maybe thats why its not open all the way. I also noticed the the number 1 on the distributor is pointing toward the transom instead of the carb as I would have thought, I don't think that should matter just cosmetically 180 off.

Is it possible since its not opening all the way its staying rich and causing the run on. Should I adjust the choke or is it because the engine isn't running and up to temp that its not opening all the way.

I'm trying to get a timing light with a tach function so I can check it on the water.

Any suggestions, should I turn the barrel on the throttle a couple turns to the cable even though it looks like its working. Or should I adjust the choke.

Lastly is this the wire that goes to ground to set base mode for timing and idle adjustments.

 

[alldodge]

When cold the choke should be closed with about a 1/8 gap at top. Doesn't matter where the mark is, over time a new choke pot has more tension then and old one, so over time it will need to be moved more.

Run on (Dieseling) is caused by many things. In correct or worn out spark plugs, to rich a fuel mix, idle to high, incorrect timing. Im seeing TB-V

Look at your plugs, distributor cap, rotor and get a timing light (can rent one from auto store).
Idle should be set at 650 in neutral in or out of the water
Timing 10 BTDC (ground purple/white wire for base timing mode)
Plugs MR43T Champion RS12YC NGK BPT6EFS - gap .045


The motor should still start even if you have to give it more throttle. If it doesn't there are other things involved like carb

 

[Boater31]

Morning AllDodge, I'll have someone look at the choke as I set it today. When it opens is the choke plate supposed to be vertical or sightly off as in my picture.

I've never had a problem starting this motor. When cold, turn key on, pump throttle once, come just off idle and fired right up. When warm just a turn of key in neutral.

I'm running ngk BPR6EFS (guessing that's what you meant) gapped to .45 I got a timing light with tach function so I will check idle speed and timing today. Reading the manual it mentions something about the mixture screw being set to be emmisions complient. So I assume there's nothing I can change with that correct.

I've never had the cap or rotor off but assume it shouldn't be those since it runs fine otherwise.

 

[alldodge]

Choke plate should be straight up and down, not tilt.
Since you have no trouble starting then rotate the knob once engine is warmed up so that its straight.
Correct on plugs

It can run fine and still the cap should be inspected. Might be building up some crud when can just be cleaned away easy and reused. Don't wait fot it to start giving you trouble before looking. Its easy to remove and reinstall

 

[Boater31]

Will do all of the above. Do I need a new gasket under the cap or can I do it today at the dock with same gasket.

 

[alldodge]

It most cases, so long as its not torn its usually fine

 

[stonyloam]

i was thinking idle mixture, but that is a single barrel.

 

[nola mike]

Choke is basically a function of time. When the ignition is on it poweres the choke, heats it up and it opens . Doesn't matter if the engine is running or up to Temp

 

[Boater31]

Well I got to the lake and did the testing. The choke opened all the way up after running a few minutes but never closed anymore then the picture, it did start right away so I didn't adjust it. I cleaned the distributor cap but of course gasket broke so new on the way. Using a timing light tach, idle was just over 700 so backed it down to 650 and timing seemed dead on, maybe between 10 and 11 but the paint Mark on balancer was kinda wide so might be dead on. Either way didn't change it. All said and done it ran great and shut down as soon as key was turned. Thanks again for all the help.