I installed it last year and have been struggling to fix the rich idle ever since. It runs great everywhere else in the RPM range. However, I literally leave a huge cloud of black smoke after going through a slow no wake zone. The engine coughs and sputters until it clears out and then runs fine. Originally I thought it was just the below water exhaust which probably did not help the situation. Now I have branched off the exhaust to let it breath above water. However, this did not really help my rich idle problem. The cold water issue makes sense. I ran it up in Eagle River WI last weekend (2 weeks after ice went out) and it ran terrible. Even if I slowed down for 30 seconds it acted up. I'll play with it more this week to see if this fixes it. I tapped into the main water cooling line right after the sea water pump for the intercooler. I might try putting the tee later in the system - i.e. after fuel cooler, oil cooler and power steering cooler. This might help slow the flow to the intercooler at idle.

I think you can eliminate your issue by force feeding the intercooler. You will pull the water away from it at idle. I imagine it's even worse this year since it was so cold.

You have to be careful by changing the point at which you pull water. That engine will not tolerate any detonation. By getting the water from a place farther down the line, you may help the idle and low speed but you could cause a rise in intake air temps at higher rpms. That is something that you don't want to do. Those Hyper-U-crack-it pistons will not take any detonation, so you don't want to raise the IAT's under boost.
Eddie

duplicate

Group, just wanted to follow up. Finally fixed my issue. It was the intercooler working too well at idle causing a cold engine situation. I installed a low crack pressure stainless check valve in line. It opens at 4.5 psi so it prevents flow at idle. It opens and flow well after 1500 rpms. Completely eliminated my issue.

part available on amazon
Duda's 3/4" NPT Check Valve In-line Low Cracking Pressure 304 Stainless Steel WOG1000

Thanks for the help.

Low crack pressure valve
 

Did you find your sea pump getting to hot while at idle before getting water pressure above 4.5 psi? Think of adding flow restrictions to the inner cooler to my 500efi whipple motor.