454 overheats when over 3000 RPM's need tech advice1

griff4

griff4

Member
Mar 19, 2013
115
Saint Pete Beach, FL
Boat Info
2007 Bayliner 325
Engines
2 350's w/Bravo II drives
Our boating pal has a classic Carver Santigo with a pair of 454's. The engine gauges indicate that things are getting hot when over 3000 RPM's. I had suggested to him that he should seek-out an "old salty marine tech" who is experienced with 454 problems. Does anyone have any suggestions or recommendations? I told him that we need not "invent the wheel" with this and that there must be some old timers out there that have seenhis before. Thanks for your expert advice! Griff4
 
Any engine cooling problem you need to start at one end and run through the whole system..

Raw water side first:
Intake thru-hull clear?
Hose to strainer?
Strainer clear?
Hose to raw water pump?
Raw water pump?
Hose to engine?
If raw water cooled block, is there sediment in the block?
Thermastat?
Hose to heat exchanger?
Heat exchanger leaking or partly blocked?
Hoses off the heat exchanger kinked or blocked?
Exhaust manifold, risers and elbows blocked?

Fresh water side (if applicable):
Coolant level?
Leak in system?
Water circulator pump?
Any hoses kinked or blocked?

Its not a 454 thing, all marine engines are similar.

Good luck,
 
My dock neighbor has an over heating problem right now. I suggested taking the thermostat out to see if that was the problem. It was really rusty. He closed up the housing and ran the boat at idle for a while. Seems the problem is gone.


Bad thermostat?
 
I've got almost the exact same problem, different engine. I'll report back if/when I find out what it is but it's most likely a blocked passage way or narrowed passage way. Like it was suggested start at one end and go to the other.
 
with twin 454 inboards u can tie it to the dock and bring up the rpm and see how much water comes out on each side. i had an impeller come apart and get stuck down stream in an oil cooler.
 
I just solved my overheating problem. Scale had built up and clogged a cooling port. It wasn't completely clogged which is why I never noticed it before during winterization. I opened up all the blue plugs and stuck a piece of copper wire in and wiggled it around. A bunch of tiny pieces of rusty debris came out and water flow poured out like crazy afterwards. I spoke to the service manager at my marina and he said It was most likely like that from all the time the boat Sat since it is raw water cooled and it just collected in one spot, slowing water flow. I didn't get a chance to take it for a ride but I'm pretty sure it's solved. I had it sitting at 4,000 rpm's for 4 minutes and temp held perfect. I'll check the T_stat next week.
 
AFD said:
I just solved my overheating problem. Scale had built up and clogged a cooling port. It wasn't completely clogged which is why I never noticed it before during winterization. I opened up all the blue plugs and stuck a piece of copper wire in and wiggled it around. A bunch of tiny pieces of rusty debris came out and water flow poured out like crazy afterwards. I spoke to the service manager at my marina and he said It was most likely like that from all the time the boat Sat since it is raw water cooled and it just collected in one spot, slowing water flow. I didn't get a chance to take it for a ride but I'm pretty sure it's solved. I had it sitting at 4,000 rpm's for 4 minutes and temp held perfect. I'll check the T_stat next week.
Click to expand...

i hope you are right, but to be honest i don't think you found your problem....the 'stuff' you broke loose at the blue drain plug was likely just some sediment that had crusted over and collected around that plug hole...i suppose it could be possible that you broke up a clog in the water passage by wiggling a wire around the plug hole, but i doubt it.....running the engine at the dock while not in gear is not a real test of the cooling system.....the engine does not have enough load on it to properly stress the cooling system...the real test will be when you take the boat for a ride and have the force of the prop restricting the rpm's of the engine....this will cause the engine to want to run hotter and will require the cooling system to be efficient at bringing the temp down to normal range....

good luck....

cliff
 
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AFD, I agree with Cliff. But I've got my fingers crossed that your right. There's a bigger problem here waiting to show it's ugly head. I still hope you are right
 
I know I wasn't really stressing the cooling system by spinning at the docks but the temp dropped at idle from 170/175 before to 160/165 and without load just revving, I was noticing the temp climbing before and now it holds steady.

I would have gone for a ride but did.t have time and today is garbage weather and I'm leaving for Vegas in the morning. One of the passages was almost completely blocked before.
 
I'm going for an M R I in the morning and you're going to Vegas .... what's wrong with this picture? Enjoy! send photos! The fireman in me has other words that can't be posted here :grin:
 
Well the fireman in me has been wasted since 7am eastern time friday morning and I just lost more money than a new dinghy on the tables...don't tell the wife. :smt018
 
griff4 said:
Our boating pal has a classic Carver Santigo with a pair of 454's. The engine gauges indicate that things are getting hot when over 3000 RPM's. I had suggested to him that he should seek-out an "old salty marine tech" who is experienced with 454 problems. Does anyone have any suggestions or recommendations? I told him that we need not "invent the wheel" with this and that there must be some old timers out there that have seenhis before. Thanks for your expert advice! Griff4
Click to expand...

I had the same exact issues and it turned out to be the exhaust flaps. Removed them and runs cool as can be now.
 
speakrdude said:
Yeah, Were they stuck, melted, what happed?
Click to expand...
Oh...whew. I thought you were going to tell me that taking them out is the stupidest thing I could have done...LOL.... Mine were melted and had broke off and were causing a partial blockage. My temp was ok right up to 3000 rpms then she would overheat. Check the manifolds, risers, water pump...etc with no luck. Then checked the flappers and their they were. Been running perfect temp ever since (knocking on wood).
 
The intention of those flappers is to keep sloshing water from entering the manifold (think of them as a one way valve). You may want to conciser replacing vs removing entirely.
 
I installed new ones and they seem to be tight. I suppose the exhaust produces enough force to open.
 
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