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Carbon Buildup two 440's

wh1278

wh1278

Member
I have two 440's that were rebuilt two years ago. Unfortunately the boatyard did not put the thermostats in when I got the boat back. So, the engines have been running cool the whole time, with mostly low rpm. Now I suspect carbon buildup as they both run rough, especially at start up. The plugs had some carbon and I peered into the spark plug holes and it looks like there is quite a bit of carbon. So, what is the best way to clean it out...Seafoam? Combination of fuel additive, plus thru the PCV intake? Any advise?
 
Re: Carbon Buildup

Try the fuel additives.... some of them actually work.

Bringing temperature up will help, but there is a limit to this if Salt Water cooled (I.E. raw water cooled running in salt water)
Salt crystallizes at temps much above 140*F.
If Closed System cooled, you can bring this closer to 160*/180* and have no problems.
The exhaust system should run much cooler anyway.

If you are continuously operating at low RPM, you may want to look into low speed fuel metering. Make changes accordingly and carefully.

Also varify your ignition advance curve and TA limit RPM.
(see your OEM specs for this)
This is best done (IMO) by using degree markings on the crankshaft balancer, then strobing this with a timing light.
Increase RPM as you strobe..... note the readings @ various RPM to the point of reaching the TA limit......, and jot them down.

Best to do this with your timing light set to standard strobe mode.
I know that some of you guys love your digitally advancing timing lights, but I always want to view this in "Real Degrees/Real Time".

Your call! :)

.
 
Re: Carbon Buildup

In the words of Ray Millanson (who taught me much about motors as a kid): "Run the s*** out of it!"

First of all, you need to get the motors up to temperature. Marine engines--though they work hard--tend to run cooler than in automotive service, thanks to that massive body of cooling water out there. And that's with the correct t-stats! Not only have you got carbon build up, you've also got acid build up in the oil, and that leads to sludge and bearing damage. So warm 'em up and run the s*** out of them soon as possible.

Jeff
 
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