Crusader 454 XL runs too hot at idle speedhelp

"After three weeks of working

"After three weeks of working on my 1994 twin 454 XL Crusader engines to resolve over heating issues, I think I have made some progress; however....I need some help. I have replaced the heat exchanger on each engine, the fresh water thermostats (170 degrees) in eaach enigine, the raw water pumps on each engine and cleaned the oil and transmission coolers. The port engine is running like a charm...holding at about 170 degrees at both an idle and running. The starboard engine is another story and where help is needed! The starboard engine runs hot at an idle...it creeps up to as much as 200 degrees. I removed the fresh water thermostat in the starboard engine to see if it made a difference....it really didn't! At idle the engine temp creeps up way too high(200)...when I run the engines, the starboard engine cools back down to about 170 and runs great. I know it sounds like a raw water pump problem, but I changed it out AGAIN today, so it can't be the raw water pump......any thoughts.....I believe there is a thermostat in the raw water system...is it possible that it may need to be replaced....per the manual it is a 140 degree thermostat. Don't know what to try next.....any suggestions are appreciated."

No t-stat on the raw water sid

No t-stat on the raw water side. (The 140 is used for Raw Water Cooled engines.)

Check the strainer where the water comes in. Might be a restriction due to barnacles or etc. That would account for it running cool at speed as water is rammed into the intake.

You can compare the flow of water coming in to the other motor by pulling both hoses off and watching. And be really sure there's no air leak before the raw water pump.

Jeff

"Check to make sure the sea co

"Check to make sure the sea cock is open all the way first.

Check the exhaust elbows (STBD) for a restriction where the cooling water dumps into the exhaust flow.

Once you get your ear 'tuned' for it, you may be able to hear the difference. Run the port and see if it quiets down after running several seconds...then try the problem child, see if it starts loud and stays that way."

Thanks....tomorrow I'll tr

Thanks....tomorrow I'll try your suggestions and let you know the results.....any other thoughts are appreciated....the elbows and risers were replaced about two years ago.

"Also have at it with a temp g

"Also have at it with a temp gun,and how did you clean the u -cooler."

"Hot slow, but cool fast? Tha

"Hot slow, but cool fast? That's weird. Is the alternator belt slipping at idle? Yes, use a IR gun and shoot the HE coolant output side, going into the coolant pump. Also, check the raw water output temp. from the HE.
Bottom line, if the coolant is cool going into the coolant pump, AND the termostat housing is hot, then I'd think a reduced flow on the FW side. I can only think of a thermostat issue, or slipping belt. OR, exhaust gas getting into the coolant. Is this engine totally stock?"