Another 3.0L overheating at high rpm

OK, I've read all the forum reports about this issue and have been through the same routine as everyone as far as replacing all the cooling system parts. My engine used to run around 170 all day long then it started to run close to 190 and above. I replaced the usual,waterpump,poppit valve assy. and thermostats. Still ran hot over 3000RPM. Found a cracked exhaust plate and replaced that asembly. I have installed special scoops on lower unit (factory authorized) to increase water pressure. Heads have been removed for inspection and checked cooling system throughout for restrictions. Now engine runs at 190-196 and water pressure at 3-4000 rpm is @10 psi. Still seems too warm for me.For the heck of it, I installed the replacement washers in place of thermostats and temp increased to 200 and water pressure dropped. Will go back to thermostats,but engine still runs too hot for me. Any other ideas guys? I love my engine,it runs great,But I don't like the temps.

Re: Another 3.0L overheating at high rpm

Carb or EFI?

How long have you had it and when did this condition begin?

Where are you?

What color are ALL the piston domes?

What is your WOT RPM?

What fuel and oil are you running?

Re: Another 3.0L overheating at high rpm

This engine is a 1996 w/carbs. I've had it for about 7yrs and has started with the heating promblem since last summer. I don't run it as much as I should being that I live in West Palm Beach. Its runs @ 5500 at WOT. I've been running regular gas and Mercury oil. Does anyone think ethenol is having an effect on engine Temps?

Re: Another 3.0L overheating at high rpm

Generally, factory jetting is plenty rich, enough so that the 10 % alky displacing gasoline is NOT an issue, HOWEVER, float height MUST BE correct, by the book, any lower float settings and piston dome coloration is less than black, which is your first indicator of combustion temp rise.

Racers regularly jet to obtain a paper bag tan/brown, BUT, they are replacing pistons regularly, often because of a melt down. DO NOT TRY THIS AT HOME.

The biggest issue with alky in the fuel is the corresponding water attacking the carb, corrosion requiring regular cleaning and the addition of water separator filter(s).

Some V6 heating issues have been found caused by a small gasket failure between the engine block and the lower exhaust adapter plate, some have been caused by sand or organic matter clogging the water path in the same adaptor plate. Both require lifting the power head, inspection of the plate and replacement of the gasket since you've now disturbed it.