www.iFourWinns.com

Ok, I have not made it back to the boat yet. Tomorrow (sat) that is my project. I'm not 100% sure how to check the risers though? I can check each of the hoses though. Your explination is awesome though. It has to be flowing, thrermostat doesn't seem to be an issue as when i'm at idle, it holds a constant 140-150 temp.

So where do I start with risers? could it be that the impeller that blew and lost a blade is lodged in there?

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94 258 Vista
5.8 OMC Cobra EFI/V8 OMC Cobra outdrive.

The first thing to do is check how hot they get, I use an IR temp gun, on mine at idle after it warms up they are about 100 degrees (this is warm but not hot to the touch) and after running on plane they are 130 or so, this is almost hot but you can keep your hand on it. IF you can't they re probably too hot.
If they are getting really hot then they are most likely clogged by rust.
To check thoroughly, you have to take em apart, there are usually 4 bolts that hold the riser to the manifold, but you must drain the water first from the manifold or else it can run down the cylinder when you remove the riser and it breaks the seal of the gasket between the manifold and riser. You also have to loosen the exhaust hose.
Is the boat in the water, if so this is a job best done on land because water can come in the exhaust pipe depending on how the boat sits in the water.

there are usually 4 smaller passages around a square center exhaust passage in the mani and riser, if these smaller ones are clogged up thats it. You will probably have to replace em then, hope you can get parts.
Is this a salt or fresh water boat?

also check the nipples on the manifolds where the hoses are connected for obstructions. Having hoses pop off on an open cooling system is very uncommon, there has to be a clog or obstruction somewhere.

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

This is great Guidance LouC! thank you so much! I'm headed to the boat today. It is in the water, and thought my first step would be remove 1 cooling hose at a time to see if an obstruction was in there. If I come up empty handed, pulling her out of the water and starting your process is step two.

Aint boating fun

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94 258 Vista
5.8 OMC Cobra EFI/V8 OMC Cobra outdrive.

Also before you pull it out run it both at idle and running speeds and check how hot they get. If you don't want to run it at speed, because of the possibility of the hose popping off just run it at idle for about a half hour and see how hot they get.

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Thanks! Also, i'm not sure if this is connected, or points to anything, but as I accelerate the engine I get a belt squeal. Could the blockage be at the pump?

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94 258 Vista
5.8 OMC Cobra EFI/V8 OMC Cobra outdrive.

nah probably just a loose or glazed belt.
Another thing I thought of...before you pull it...disconnect the feed hoses to the manifolds at the manifolds. The just for a minute, start it up, with someone watching, water should spurt out of both of them. If not you need to look at your thermo housing, if water does spurt out then it's the manifolds/risers. Note: only do this for as long as is needed to see the water flow, (really probably like 10 sec or so) or else the manifolds can get really hot.

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Ok, Spent the day at the boat.

Risers --> Clear and unobstructed (gaskets on order to re-install)

Thermostat housing --> Clear and unobstructed.

So...here is what it leaves me with:

The "T" where they pull off warm water to heat water for my hot water tank is a simple, non-barbed or beveled fitting. Could it be that they were simply loose? Thoses were the fittings that popped off, one.... then the other. I have 40+ hours on the boat this year? Seems too unlikely that it popped after replacing the impeller on the outdrive?

I think the idea of running it and seeing if water is coming out of the drains on the manifold is a great one Now I can see if the water stops or is not exiting at that point. I have employed the local marine mechanic to order the gaskets for the risers, he is just as puzzled as we are? He has offered to run the boat with me and try and shed some light when we get the gaskets in on Tues.

Got to tell you, this one has me pretty puzzled!

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94 258 Vista
5.8 OMC Cobra EFI/V8 OMC Cobra outdrive.