Mercruiser running rich?

[RatFish]

After fogging my engine, I pulled the plugs to put fogging fluid in each cylinder. When I pulled the spark plugs, I noticed that the tips were oily. That was expected. What I didn’t expect was what I thought was excessive carbon deposits, like the engine was running really rich. <br /><br />My power plant is a 2004 5.0L carbureted Mercruiser, Alpha 1. The engine has about 65 hours. When I changed the oil at 20 hours, I put in 25W-40 Mercruiser oil (dino). I used 93-octane fuel all season because that’s the only grade fuel available at my local Marinas. The engine is raw water cooled. Most of the time I put on the engine was under heavy load (skiing and tubing). Any thoughts on how I should correct the problem?

 

[tommays]

Re: Mercruiser running rich?

the only way is to change the main jets in the carb with a tuneing kit if they make one for a merc carb one step at a time till they the plugs get toward a nice brown<br /><br />i think it will end your merc coverage if you tinker<br /><br />its a very trail and error job but the end result will be good<br /><br />tommays

 

[Laddies]

Re: Mercruiser running rich?

Is your engine running up to temp. a bad thermostat will cause it to run rich or a rich choke setting is not to unusual from the factory--bob

 

[RatFish]

Re: Mercruiser running rich?

tommays,<br /><br />It does sound like some carb adjustment is needed. The boat is winterized now so I’m going to have to follow up in the spring. After I bring her out of storage, I will put in a fresh set of plugs and start from there. The engine is still under warranty so that is a concern.<br /><br />laddiesservice,<br /><br />The temp gauge averages between 175-180 degrees when warmed up. I’ll add choke operation to my list.<br /><br />Thanks to both of you.