It appears that fouling out my plugs seems to now be a regular occurance lately. Probably has to do with now that I have my boat at the yacht club, I have a 15 minute idle down the river before I get to the open waters.
I have already bumped the heat up one range to try and resolve the issue, but no luck. I am running NGK plugs BKR5ES11. I have no soot on my transom. I worked out the richness issues last season and I should have the right jets in there now, but last season I didn't do nearly as much idleing.
My carbs are fairly new Holly's 750 cfm 4160 with 4150 secondary blocks (so I can change out jets).
Any suggestions?
I am thinking there is a idle mixture adjustment that needs to be done, but not sure exactly where that is? How much to move it? And what direction to move it?

best way to set idle mixture is with a vacuum gauge, here is one link on how to http://www.chevyhiperformance.com/howto/45638/

Do you have a big cam in the motor? If so, take the flame arrestor off and look down into the primary. If you see fuel dripping out of the booster you may need a different power valve.

The cam is fairly big... the largest roller cam that my builder was comfortable installing with wet exhaust. I will check that out and see if there is fuel drizzling out.
We did adjust the mixture with a vacuum guage initially last year. But it is an extremely touchy situation... the guage bounces a lot, etc. And at this point I was thinking I would just back off the screw a little at a time, but I don't know which screw.. I'll check that web page.

Try and get best average vacuum reading at idle, power valves should be about half of that reading.

I ended up with 2.5 power valves in order to get them to stay closed at idle.

Good article.

Found another good one on power valves

http://www.chevyhiperformance.com/te...ems/index.html

and this http://www.mortec.com/carbtip1.htm