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riers running hot

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wildfrahm

Contributing Member
Hello, I am having a iratitaing issue. After have been running say over an hour my manifold and raisersget hot but not engine. Theirs time it happened it melted the exhaust tube. Still ran but loud, brought home flushed engine as always, removed manifold and raisers and acid dipped cleaned( they are just about brand new) reinstated. Took boat out there was slight leak in raisers basket that water was shooting of.I took laser heat tester with me engine ran great opened up engine compartment and checked temps ever so often everything was fine. Elbows ran around 90deg and manifold ran around 170deg. When I pulled up to dock to leave I opened to check and there was no longer water spraying from leak and temps were sky high. Manifold 300+ and elbows approaching200deg. Engine was at 165deg and running great. Took home ran on cuffs to flush out for almost an hour nothing got hot at all.Have had one tell me it was thermostat and on says it's the water circulating pump, nothing sounds right to me, any ideas.
 
You did not state year, motor, drive system.

When you took off the risers you have a flapper / shutter in the exhaust tube or tubes if a v6 or v 8 ? Or did it melt off and is blocking the exhaust down further in the tube or the exit at the rear that goes to the drive.
 
It has melted away I have new but have not installed.Buy the way it is a mercruiser 260R (350 5.7) installed in a 1984 26' wellcraft. I have great flow out the out drive when running.
 
Took boat out there was slight leak in raisers basket that water was shooting of.
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Ayuh,... You do realize, that if it's leakin' outwardly, it's probably also dumpin' water Into the motor, exhaust side too...
When I pulled up to dock to leave I opened to check and there was no longer water spraying from leak and temps were sky high. Manifold 300+ and elbows approaching200deg.
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That's a lack of water flow, from the raw water pump...
Donno why, but that's what it's sayin',... Maybe some old impeller pieces somewhere...
 
After you replace the riser gasket to make sure you are not leaking water into your engine. Pop off the drive and look for the old pieces of flapper inside the bell housing and inside the drive. Also replace the complete(With Housing) water pump in the lower if it's an Alpha drive.(Don't look at it and say "it's looks good" and put it back)
While you have the drive off remove the water feed line from the t-stat housing and force water backwards through the hose. Do this to make sure you have no blockages.

BTW, How old are the risers and manifolds? Just because the look good does not mean they are good.
 
Okay, temp gauge at helm is accurate. I have a temp gun that reads where ever I put dot. I do not know where rubber from flapped went but it melted away the first time it happened. The manifold and raisers are less than 2 years old. But I have bought new raisers and have on hand. Am trying to get plan together before I start. Yes I run a alpha 1 and water pump and housing are less than a month old. I melted one before urge one on there now. I back flushed system before in installing the gear case because there was species in the pickup channel in the gear case. I also believe I found some when I soaked the raisers/manifold.u
 
Think when I replace raisers I my replace thermostat also. I can leave thermostat out and flush block and hoses, the whole systems and look for blockage. I could also have a price footing around in the tstat housing getting caught up by the check balls. Hello i'll take them out also.
 
...water pump and housing are less than a month old....
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Did you use "Perfect Seal" or similar sealer on the lower gasket on the top side of the impeller? I believe it keeps the impeller from sucking air. Correct me if I am mistaken.
 
Neither one of my manuals say anything about using sealant. Like I said I have water flow on muffs and runs great on water olny happens after awhile underway.
 
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