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1986 454 1 exhaust manifold hot.

S

sammi

Regular Contributor
What would cause the starboard manifold to be hotter than the port. The port one I can touch forever but the starboard one is close to too hit to touch. Temp gauge reads 140. I replaced the raw water impeller and raw water belt. No improvement. Removed thermostat no difference. A circulating pump can't quit working right? Its just a metal impeller that spins true? 1986 raw water cooled fresh water lake Erie boat. The impeller I replaced had all its fins.
 
I'd start with a corrosion induced restriction at the water injection ports in the elbow on the hot side.

circulation pumps can quit but don't do so often.
 
I guess I have to break down and remove the riser and take a look. The bolts that attach it are some sort of star bolt. Not a hex hut. Does it require a special tool?
 
Agree. Look at the manifold-to-elbow sea water transfer ports.
Warm the engine up before cracking these bolts loose. Better safe than sorry.


Also, somewhere in your system, the "spent" sea water is being divided as to flow equally to each exhaust manifold.

This may be a raw water cooled engine T-stat housing, a splitter fitting after the Heat Exchanger, or a dual outlet Heat Exchanger.
Look and make sure that this is dividing the flow equally.


Don't be talked into restricting the cooler side. Rather find a way to gain more flow to the hotter side.



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Yep.... the T-Stat housing should split or divide this sea water equally, so that each hose #3 sends an equal amount to each manifold.

I just recently had to take a die grinder to an OEM T-Stat housing as to help create an equal flow.

If the T-Stat housing is doing it's job correctly......., then you likely have a restriction at the manifold/elbow transfer ports.




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OK, dumb question but could I remove the inlet at the front of the manifold and spray a garden hose in the hole with my hand around it to see if I could force out a small clog or would that force water into the cylinders somehow. Its not too hot to touch but the other side is lukewarm at best.
 
This is your expensive Marine Engine. I'd not short myself on this.... it's just too dang important to NOT completely look at all potential areas of restriction.

Roll your sleeves up, and get dirty! :D
Or hire this done by a qualified person.

No offense to any DIY'rs..... but those who try to save a few $$$ by winterizing themselves, or by trying to short-cut an over-heating issue, usually kick themselves for not having taken the correct measures in the first place.




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Fair enough. My issue is most problems on this board start with ....."after rebuilding my engine or.......after replacing my manifolds and elbows..... I have a leak or #8 cylinder is full of water." 2 weeks ago that manifold was lukewarm so I just can't imagine rust built up that fast. I guess tonight I'll take the hose off and see how much water is coming out. Rule out as much as I can before removing the elbow.
 
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I pulled that big one inch plug at the bottom of the riser out. Behind it was a big clog of dirt mud and crap. I'm not sure if I can get it all out without removing it or not but I seem to have found my problem.
 
Well I pulled the riser and elbow off and they look great.everything wide open. I knew I shouldn't have done that. Lake Erie boats never need new manifolds--ever. Never heard of bone going bad. Now I need to find gaskets to put it back together. I guess no boating for me on July 4th weekend. Now I don't know what the problem is though. I filled a bucket of water from the inlet hose in seconds. Idk why that side won't cool.
 
In the bottom of the manifold it looks like there are " end caps" it looks like held on with a long rod. Can I remove those and take a look? Are the caps reusable once removed?
 
Hi i am new to this site. I am a motor Mechanic and i have been reading a few posts on starboard risers getting hot. I own a 92 raw water cooled. 5.0 V8.

My star riser is very hot to touch,.... i have repalced both manifolds and risers, new raw water pump, new circulation pump. Ive built the drive with every oil seals as water was mixing into my oil so i also fitted a new pump and housing... I have also changed the tstat. 140. Note ive fitted the gaskets that came in my manifold kits, 2 slots and 2 holes as a restrictor. running motor in sea water i have good flow form the sea pump to the t housing. as the motor warms up the star hose from the tstat get hotter than the port. I pulled both hoses off and i have roughly the same flow, however hot water is coming out the starboard side while the port is cool...... I thought maybe a blockage in the exhaust so ive pulled the risers off and the flappers look in good condition and i can pure water pass then both ok.

Any ideas will be great Steve
 
Sounds like a mecruiser outdrive....did you check the thermostat housing, where the water exits to go to the manifolds?
 
Unless its relatively new, the tstat housing, where the water exits, has poppet valves in the outlets...if malfunctioning, they inhibit water flow on that side...the newer style eliminates the poppet valves and just uses a fixed restriction.
 
makomark said:
Unless its relatively new, the tstat housing, where the water exits, has poppet valves in the outlets...if malfunctioning, they inhibit water flow on that side...the newer style eliminates the poppet valves and just uses a fixed restriction.
Click to expand...

I can see straight throught both exits... however the water in splits off to 2 levels. That was really bad. Ive just acid bathed it and its cleared all passages. Will try this. Ive replaced the sea pump also however if it still gets hot ill use a hose pipe for the water in and imcrease pressure. See if that helps to rule out any problem in the leg.

thanks

Steve
 
Steverobbo79 said:
I can see straight throught both exits... however the water in splits off to 2 levels. That was really bad. Ive just acid bathed it and its cleared all passages. Will try this. Ive replaced the sea pump also however if it still gets hot ill use a hose pipe for the water in and imcrease pressure. See if that helps to rule out any problem in the leg.

thanks

Steve
Click to expand...

Ok I have done a bypass using 2 hoses. 1st hose is feeding the drive so I dont burn the pump. Second hose is directly feeding the main thermo housing.....on full pressue. Ran motor and star riser gets hot....... take the hoses off the thermo housing that feeds the manifolds. Stars water flow is ok and hot. While port is cool......And I missing something here. The housing looked ok after a clean just doesnt seem to be getting even temp. My thermostat is a 140. Does anybody know why it running like this.
 
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