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Exhaust riser temps

mike1970

Member
"I have a 1998 4.3 merc. I jus

"I have a 1998 4.3 merc. I just had new manifolds + risers installed. Now the starboard riser is warmer than the port side which is cold.There is good water flow to each side, but what I noticed is that the hose going to the starboard manifold from the thermostat housing is warm and the other is cold. Obviously the warm water coming from the engine is exiting thru the stbd manifold. Shouldn't it be equal between both sides? It does this both in the water as well as on the trailer. Any advice would be greatly appreciated."
 
This truly is the year of over

This truly is the year of overheated starboard manifolds and risers. There have been many posts in the last 3-4 months about this issue on various V-6 and V-8 engines.
You should do some searching and read a few for ideas.

What caused the need for new manifolds and risers?
I wonder if the shop that did the work installed the right gaskets between the risers and the manifolds. There are three different gaskets available depending on the application.

Give us more history on the original problem.

Rod
 
"Rod- I purchased the boat and

"Rod- I purchased the boat and it had the one piece manifolds,which I was told were a bad design. Plus the boat was 12 years old, so I decided to replace them. The shop replaced them w/ the normal 2 piece manifold & riser and the adapter kit to hook up to the origional exhaust pipe. The engine does not overheat, but what I did notice is the water flow exiting the boat, just after starting, is normal and cold from the port side, but from the starboard side, water flow does not start right away, about 30-45 seconds later it starts flowing, and it is hot.
I haven't opened the thermostat housing yet, but I know there is a spacer that goes in after the thermostat, and it has 2 notches in it. Do those notches allow the water to exit to the manifolds? could it have been installed wrong? twisted, to allow the hot water from the motor to exit to one side only? could that be why there is a delay in water flow to the stbd side? after the thermostat opens?
I have a good mechanical backround, and am just trying to figure this odd problem out.
thanks,
Mike"
 
"Ayuh,....

It's Perfect


"Ayuh,....

It's Perfectly Normal for 1 riser to be warmer than the other....
Usually, but not Always it's the Starboard riser that's warmer....

I've found this to be True with All V-motor Chevies...."
 
"Does yours have the second se

"Does yours have the second set of hoses attached to the riser bases that come from a T fitting on top of the stat housing?
If so, I would check the fitting and hoses for obstructions.
There is a check ball assembly that is fitted to each outlet of the T fitting, that often fouls and jams up. I would give it a checkout if so equipped.

Rod"
 
"Rod-
this does not have the


"Rod-
this does not have the 2nd set of hoses, only 1 for each side going from the thermostat housing to the manifold and no check balls in the housing"
 
There is a bypass hole inside

There is a bypass hole inside the T'stat hsg. It can be inspected by removing the plug on the underside of the hsg. Hole diameter is 1/2" and can become narrowed by debris or enlarged by corrosion.
 
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