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Riser heating up too hot to touch

 
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bayratt



Joined: 29 Jun 2009
Posts: 1
Location: Wantagh, NY

PostPosted: Mon Jun 29, 2009 12:08 pm    Post subject: Riser heating up too hot to touch Reply with quote

I have an OMC 1995 Ford 5.0 litre on a 20 ft four winns that just had an overheating problem (port side completely melted the rubber hoses after the riser). Turns out 2 of the manifold ports were completely blocked (acid bath for 2 days didn't unclog it). These manifolds were supposed to be new (bought boat a year ago), everything looks clean inside and out of manifold, no rust, so the clog was a surprise.

Anyway, after getting a new manifold and inspecting as much as I could see to make sure everything is clean, I put everything back together and it sounded like it was running fine. I took it for a ride and the manifolds are both barely warm (cooling well), and the sides of the risers were the same. The top of the risers on the other hand were extremely hot. After the first 5 inch rubber hose the metal elbow that leads into the exhaust was hot, but i could tolerate the heat when holding my hand on it.

When I bring the boat up on plane (thinking more water should cool it down) the tops got hotter and the elbows are the risers were also too hot to touch.

My only thoughts are that maybe a port is supposed to be blocked to create more pressure to get the water up to the top of the riser? Sounds far-fetched, but I'm at a loss here. There were no blocking plates and it ran fine last year.

The water pump is not on the outdrive, it's on one of the belts of the engine, and that looks good based on a quick inspection. I also pulled the hose that feeds the thermostat to see what kind of pressure was coming out when the engine idled - it looked strong.

Any ideas??? I might guess that it could be a bad riser, but both? They both look new inside and out.
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MikeW
Senior Member


Joined: 01 May 2006
Posts: 680

PostPosted: Wed Jul 01, 2009 3:10 pm    Post subject: Reply with quote

Helo sounds like the risers might be plugged. Feel free to call me at 800-998-9508 Cool
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