1989 454330 overheating

"Hi guys. New here, and I appr

"Hi guys. New here, and I appreciate your feedback. 1989 454/330 Crusader running hot above 3000 rpm and when under a load. Closed system.
Step 1 - strainer clean.
Step 2 - back flushed seacock for 30 minutes. flow seems strong.
Step 3 - rw pump belt new and tight.
Step 3 - inspected raw water impeller. looks fine. pump housing looks fine.
Step 4 - disco rw feed to oil cooler. pumping water strong.
Step 5 - disco rw outlet from oil cooler - strong flow.
Step 6 - remove exchanger end cap - looks clean.
Step 7 - remove tstat and tested on stove. works fine and opens at 150.
Step 8 - replaced water hose from seacock to strainer. (soft spot).

Flow inside exchanger seems light. Any chance the water pump on the block is bad? No leaks anywhere.
Hoses all seem fine. AF is clean and 50/50 mix. Engine always runs at 150 until last week. Risers/Elbows 2 years old. Running at lower rpm's under load causes slight rise, but not mor than 160-170 degrees or so. 3200 rpm means 200 and alarm condition. drops to 150 after a few minutes at lower RPM

Thanks guys."

had the exact same problems -

had the exact same problems - ended up being the hose that brings antifreeze back from heat exchanger to water pump was sucking shut at high rpms - disconnect throttle from carb then rev by hand as you watch hoses

Thanks Steve. Good advice. I w

Thanks Steve. Good advice. I will put it on my check list. What is that a 2" hose?

It's about 2" on the 4

It's about 2" on the 454 XL it connects to the bottom of the h.e. and runs the length of the engine to connect to the circulating pump in the front.

"How old are your manifolds an

"How old are your manifolds and risers? If you don't have adequate flow of the raw water, the heat exchanger is never going to be able to keep the engine cool. I'd take a looksee if I were you."

manifolds have nothing to do w

manifolds have nothing to do with raw water flow in a freshwater cooled engine - they should last the life of the engine itself.

"Excuse me! Tell me then, how

"Excuse me! Tell me then, how is the raw water,(Which cools the heat exchanger) discharged if the manifolds are clogged with rust?"

"By manifolds, as a general st

"By manifolds, as a general statement, I am refering to the exhaust system. Most specifically the risers."

"Turns out it was the belt tha

"Turns out it was the belt tha drives the circulating pump/alternator.

The risers/elbows are 2 years old. Heat gun test revealed the tempt to be about 130 on each side.

Pulled off the end cap of the exchanger and ran a rod through it. No blockages. Swapped the impeller and sea trialed, overheated after 20 minutes. Noticed the ammeter was low, decided to swap the belt out. No more overheating, but it is running at about 160 instead of 150. Problem solved as far as I am concerned. Thanks for the help."