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Exhaust manifold and riser too HOT to touch

94maristar

New member
"i have 1 1994 Mastercraft Mar

"i have 1 1994 Mastercraft Maristar with an indmar GM small block 350, 280 hp on a v-drive.

the issue is the exhaust manifold and riser on the port side of the engine get too hot to touch after only a couple of minutes of average use (cruising at 2200 rpm). the starboard side stays nice and cool and my engine temp. stays steady and there is no alarm.

i have replaced the old manifold with a new one from mastercraft and am still getting the same problem. i have disconnected both port and starboard water lines from the thermostat and both have the same amount of water comming from them.

do i need a new water pump? i replaced the impeller last summer and the new one has less than 2 hours on it.

if anyone has any advice it would be greatly appreciated... i am now going into the second boat season with this gremlin in the engine

cheers, ryan"
 
"Do you run in salty or bracki

"Do you run in salty or brackish water? How old are all of your risers and manifolds (aside from the one manifold you changed?) If you do run in salt or brackish, do you flush your cooling system with a "fake a lake" regularly after use?

Have you removed both risers to examine them for rust and blockage?"
 
"we were told the boat was run

"we were told the boat was run in fresh water only and i can assume that both the risers and the manifolds were original to the boat (althought the boat is a 1994, it only has 240 hours on the meter).

i dont think it was stored properly through the winters though... when i removed the original manifold that i replaced i rinsed probably 2 tablespoons of rusted metal flake and debris from the manifold. i think it was storred in a warm place throughout the winter but im not sure if the drain plugs were ever bled. the riser appeared to be in decent condition so i put it back on after i replaced the manifold. now i am ready to order a new riser as well as the problem seems to be specific to the riser. it allows water to pass through it on the bottom and sides of the "gooseneck" but not through the top channel which exits the manifold on the stern side. this of course is the area where the hot exhaust hits first as it makes its was out of the manifold and through the riser.

the engine will run at "marina speeds" all day and the riser might be slightly warmer on the problem side. as soon as you run at anything over 10 mph the top of the riser begins to heat up until it is too hot to touch and it then begins to transfer heat into the exhaust manifold. all this with no alams sounding and the port side runs and cools perfectly.

let me know if you think the riser could be causing this.

cheers"
 
"as far as running lean, i kno

"as far as running lean, i know what this means but how would i fix this?? just take it to a shop and tell them i think its running lean on the starboard side?

is there any thing i can do to check this myself?

the engine is fuel injected but it is not like a car (rail with direct port injection) it appears to have a carbuerator as well

thanks for the heads up"
 
If it is FWC check the heat ex

If it is FWC check the heat exchanger. Mine sucked up some seaweed and it caused one side to run hotter due to decreased flow.
 
so you think it might be the t

so you think it might be the thermostat?

should i just replace it or is there anything i can do to confirm that this is the problem? and should i still put on a new riser?

the flow is the same comming from both port and starboard hoses at idle but i didnt check the flow with the engine cranked up a little bit. could a faulty t-stat cause a flow/cooling problem on just one side?

thanks again... sounds like im narrowing it down
 
and its not fwc... however the

and its not fwc... however the cold lake water is drawn into the boat and through the transmission cooler first... is it possible that there could be a blockage there?
 
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