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Spark plugs confused

"Kghost and Guy: will do.

I

"Kghost and Guy: will do.

I have not tried backing the timing to 6 or 4...I've always set it on the dot at 8.

I don't have a thermometer, but I'll pay more attention to the temp when tubing/skiing."
 
Infrared laser thermometers ar

Infrared laser thermometers are available at auto parts dealers and Sears for under $40. Just Google laser infrared thermometer.
 
"That deiseling probelm with t

"That deiseling probelm with the 4.3 is not that uncommon. I have the same problem with mine (1998) and have been told by Merc. mechanics here that letting it idle for a couple minutes is the solution. I also considered changing plugs etc., but have opted for retarding the timing a degree or two, leaning out the carb., and reducing idle speed. My main problems occur when I take the boat to the West Coast where it never runs hard, but diesels like crazy when you try and shut it off. (elevation drop of 3500 feet).
I don't agree with shutting it off in gear as I once ruined a motor that way. They make great water pumps running backwards, the problem is, they suck the water in, not out.
Once I get to the Coast, (2 weeks time), I intend to adjust until I have this thing under control.
Enriching the idle mixture to me would be contrary to most advice that I've received, but I will certainly try it if all else fails.
A GM mechanic here tells me that on any carb'd motor coming from the Coast, the rule of thumb is to advance the timing 1 degree for every 1000' of elevation gain.

While not all of us are marine mechanics, we do have problems that are not everyday, and the everyday solutions don't work for us all. Let's continue in the spirit of this site to help to resolve, and share experiences, to make our pastime one of continuing enjoyment."
 
"I have the same motor with th

"I have the same motor with the same problem and it only runs-on when you get some heat in the engine after towing a skier or tube. I have tried everything .Tune-up,timing,fuel mixture clean carbon with merc tuner and seafoam,differnt fuels and higher octane fuel and still has run-on .Ill ask the experts, heres one thing noticed with my motor sometimes when pull the throttle back to neutral it idles @ 800 rpm for a minute then drops to 650 other times it drops right to 650. I have already adjusted the throttle cable barrel one turn i am afraid to adjust it more and damage or bind the cable . Can it be aqdusted more ? Would a light return spring help ?Also i noticed on the earlier post the engine temp of 150 degrees i believe he has a 140 deg t-stat."
 
"TJB:

Check the throttle sh

"TJB:

Check the throttle shaft for wear, with the cable and spring removed. If there's a noticable amount of play, the shaft's bore can be enlarged and bronze bushings installed.

The worn area around the shaft works just like a small vacuum leak and increases the idle speed, if present. Many a replacement carb has been sold to 'fix' this issue."
 
"@Guy:

I don't have an

"@Guy:

I don't have an infrared thermometer yet, but I paid special attention to the temp gauge during tubing runs (towing a very large tube with three kids, around 3200-3600 rpm for say, 6-8 minutes at a time).

Temp gauge nev"
 
"A plug gap difference of 0.00

"A plug gap difference of 0.005" more than 0.035" won't make a noticeable difference in operation. Regap them if you want to do so.

After a hard run the cylinder combustion chambers are extremely hot. Turning the key to off does not stop the rotation of the engine. A few cylinders are going to be near the TDC point and ignite from the heat just like a diesel; thus the term dieseling.

I run a Mercruiser 143 F. T'stat in my 4.3L V-6 and the temp. stays right around 140 F. and the engine doesn't diesel after a hard run on the lake. The gauge and sending unit are 4 years old.

"...the temp gauge does take a little bit to rise to 150-152 as expected."

What brand of T'stat are you using? What brand is the gauge? Is there an adjustment screw on the back for calibration? Pull the temp. sender and polish it and the elec. bayonet on it until it is bright w/some 1200 grit sandpaper or a scotch brite pad. Do the same for the back of the gauge. See if the temp. reads lower.

You can check the sending wire by disconnecting it at the sender and the gauge and substituting a temporary 16-18ga. jumper wire. If the gauge reads lower then the wiring has a little resistance.

You may just have to run a higher octane fuel to stop the dieseling.

You might try hot water to decarbon the engine. The engine should be at oper. temp. Remove the flame arrestor, engine in neutral and RPMs need to be maintained at around 1500-2000. Take a paper cup w/4-6 ounces of hot water and pinch one side of the cup to pour from. Slowly pour the water into the carb throat like you are urinating but not so much to kill the engine. The water will vaporize in the compression and combustion process and knock out any carbon. You will see it come out with the exhaust."
 
"Daniel did you get your diese

"Daniel did you get your dieseling problem cured ?I have a 01 searay 185 with the 4.3liter 2 bl carb . I had the same problem and tryed running seafoam and mercury power tune through the carb, installed new cap,rotor ,plugs and fuel filter the engine still dieseled . Next i tryed cooler spark plugs,changed original thermostat from 160 to 140 t-stat,adusted throttle cable. I set timing at factory specs and changed fuel to shell 89 octane . Ran the boat all last week towing the kids on tubes . The engine shutt off great and never dieseled . I believe like it was stated earlier in this post the main problem was engine temp,idle speed and type of fuel"
 
"No, it hasnt' been solved

"No, it hasnt' been solved yet...mainly due to another problem that cropped up (http://www.marineengine.com/discus/messages/12486/291377.shtml).

I'm glad that you had success! I'm going to continue to work on it once I feel comfortable that it's not going to die on me any more.

I thought it was strange that your original thermostat was 160....usually aren't they 143? You still have the cooler spark plugs in there?

I just found out that my mixture screw was WAY rich, but I have not been able to get the boat on the lake to see if anything has changed."
 
The original t-stat was a 160

The original t-stat was a 160 deg thermostat it was stamped on the bottum .The engine ran 160 to 170 deg and with the 140 thermostat it now runs 140 to 150 degrees . I am still running the cooler ngk spark plugs and it runs fine. Hope you get yours staightend out .
 
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