1994 OMC 5.0 Water Intake / Cooling Problem

[bkhitchens]

I have been having cooling problems on my starboard 5.0 (ford) OMC on a 1994 Four Winns 278 with OMC / VP SX drives. I ruled out impeller, gauges, sending unit, thermo, etc. as cause of problem or reason for false readings.

Today I hooked up a clear hose from raw water pump to thermo housing. at cruising speeds very minimal air bubbles and temp stayed around 160-170. When I got up on plane at WOT temp shot up over 200 and there was bubbles to ther point where it was obvious that the water flow was interrupted. I suspected this would be the case.

Is this a blockage? There seems to be plenty of water flowing when not moving or moving slowly. Is it a crack in the hose / water intake at the drive as I suspect? If so, what does it take to fix it. I believe that the boat will have to be taken out of the water. What does replacement of the hose or cleaning of the intake entail once the boat is out? Is there a band-aid fix that can be used for the season? Any help on this is appreciated.

 

[Justin Kennedy]

Re: 1994 OMC 5.0 Water Intake / Cooling Problem

Salt water use? how long since you've replaced manifolds and risers. Could have flappers stuck at the base of the y pipe. I'd look at the manifolds and risers if its been more than about 3-4 years since new, especially if salt water use.

 

[KRH1326]

Re: 1994 OMC 5.0 Water Intake / Cooling Problem

Absolutely risers and manifolds. Running low rpm, nothing seems amiss. Open her up and the existing flow can't handle the heat load.

 

[bkhitchens]

Re: 1994 OMC 5.0 Water Intake / Cooling Problem

I may be missing something here. If there is air coming in on the intake side wouldn't that be an issue there? I am thinking that there is a leak / blockage in the drive or before or with the raw water pump on the engine. I don't see how the risers or manifolds could be suspect until there is an uninterrupted flow of water to the thermo housing. Again, I am new to marine engines so any more information would be appreciated. As it stands, I am planning on pulling the boat out and taking the drive off to inspect. Thanks

 

[Monte1961]

Re: 1994 OMC 5.0 Water Intake / Cooling Problem

Ok the water and exhaust don't mix in-till at the end of exhaust manifold. If any of the water passages are restricted, it will run cool at idle, as soon as you get on the throttle, it won,t allow enough water to flow though. Make since?