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PORT SIDE RISER HOTTER THAN STARBOARD SIDE

C

Capt. Harry

Guest
"Hello Everyone! I just purcha

"Hello Everyone! I just purchased this boat with a 2001 5.7 Mercruiser Horizon MPI. Just changed manis and risers(were original O.E.), gets hotter on port side riser only while on the trailer with hose. Checked for blockages..none. THIS IS A CLOSE COOLED SYSTEM. Yes, changed impeller too! Thanks!"
 
Sounds like not enough water f

Sounds like not enough water flow. Turn on the water tap more.
Is your boat sitting level side to side?

Rod
 
"Hose tap cranked up all the w

"Hose tap cranked up all the way.....boat is level on the trailer. Pulled off lower manifold hoses that are fed from exchanger.....uneven flow,i.e. less is going to port side. Pulled off HE end caps and reemed tubes real good. Still gets hot on port side. Maybe with boat in water should be fine???? Going to pull HE and acid clean. Thanks"
 
Remove the T'stat tower an

Remove the T'stat tower and (diluted acid) clean crud buildup. The tower diverts cooling fluid to the exhaust mans. and risers.
 
Really? The thermostat tower h

Really? The thermostat tower has a raw water inlet passage that routes raw water via heat exchanger? Is this correct? Thanks!
 
"Forgot about yours being FW c

"Forgot about yours being FW cooled. Let me clarify my statement. Only if your exhaust mans. and risers are part of the FW cooling circuit. Some FW cooling is for blocks only. Antifreeze cools only the block on partial systems or the block, ex. mans. and/or risers on full systems. Even if you just pull of the hoses at the tower for a full FW colled system there may be some crud in the diverter nipples.

Antifreeze can degrade and form a gel or goop that plugs passage ways. May need to flush system."
 
"Watching exhaust exit at tran

"Watching exhaust exit at transom, much more water on starboard side exiting. Port side has more steam( much less water) exiting. Maybe performs correctly in the water? I'm thinking HE is the culprit, but I really cleaned all passages. I'd hate to burn a hole on that port exhaust side. Any good HE supplier?"
 
Thanks! But how do I know that

Thanks! But how do I know that I have an Exhaust shutter? Where is it located?
 
This boat is a straight inboar

This boat is a straight inboard Shamrock. Do you think it has the shutter?
 
"Sorry Capt., didn't know

"Sorry Capt., didn't know it was an SI engine. Is there an exhaust baffle in the hull? Sombody had a recent problem like yours. Are the entire engine, exhaust mans. and risers antifreeze cooled? I assume you have thru hull exhaust? Shutter would be on the outside if so."
 
"Thanks Guy! The engine is onl

"Thanks Guy! The engine is only antifreeze cooled. The manis and risers are raw water cooled. I have the thru hull exhaust below the water. I took another peek thru the port transom exhaust. It looks like the shutter is inside a exhaust baffle. I thought it was metal, but I can see fibers and some strands coming apart around the inside tubes close to the shutter. Also, this baffle is about 2 1/2 feet from the transom exhaust exit. I'd hate to pull everything out for nothing. On the starboard side, everything is nice and intact. So, the shutter is well inside the exhaust. You think the water flow might be restricted and that's why the riser is hotter?"
 
"Both my 18 year old 7.4L Merc

"Both my 18 year old 7.4L Mercruiser engines are running hot. They used to run 145 degrees. Last year they started running at 155 and this year under power they were approaching 180 degrees. They idle at 165. I replaced the seawater pumps, thermostats and check balls last season with no affect. I verified the temp with an infrared meter. My exhaust elbows are open and I am flowing water. The boat is a freshwater open system, however the first 6 months ownership it was operated in salt water. I run a sea strainer. Any thoughts anyone?"
 
"Try it on the water, My 5.7 r

"Try it on the water, My 5.7 runs starboard hot on the muffs but equal in the water."
 
Ever changed mans. and risers?

Ever changed mans. and risers? Probably plugged w/rust. Either pull and clean at radiator shop or replace. Best to replace. Check shutters while at it; good to replace them at that age unless thru hull exh.
 
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