1994 OMC 5.0 Cooling issues?

[bkhitchens]

I have a 1194 Four Winns 278 Cruiser with two OMC 5.0 (Ford) engines. The Port engine runs well, starts good, idles, and runs at around 150 degrees. The starboard engine starts ok, has to warm up for a while before it will stay running when shifting into gear. The main issue is the operating temp. It will heat up to around 150 degrees withing minutes where the port engine barely reads a temperature. At WOT, or close, the starboard engine will heat up to around 200 degrees or more, within a minute or two. When I back it down it cools back down to around 150 within seconds. I installed a new impeller. When I started it on muffs it did not expel water under the drive and I don't think out the prop. After installing the impeller, I believe it expels out the bottom but still not through the prop. The boat is in a slip now and I can't see exactly what is happening. I installed a new thermostat today, and no change. The housing is somewhat rusty inside, but did not seem clogged. The boat spent the first part of its' life in CT but I don't think complete salt water, if at all. There is corrosion on the drives (VP SX) but they seem ok. The impeller that I replaced was chewed up a bit but not missing vanes. I don't think there should be clogging from this particular replaced impeller. Today, I ran the boat to where the starboard engine was around 200 degrees, stopped quickly, and checked both engines with an infrared thermo. There was not significant difference in temps between both engines and nothing near the 200 and falling degrees shown on the gauge. I checked around the risers, hoses, and circulating pump.

Questions: Could the gauge be bad? What else should I check; hoses, risers, etc.? Could it be a bad circulation pump? Any other ideas?

 

[bkhitchens]

Re: 1994 OMC 5.0 Cooling issues?

BTW - I just got this boat. I am mechanically inclined but inexperienced with marine engines. I have no idea what the risers entail if that could be the source of the problem.

 

[drem312]

Re: 1994 OMC 5.0 Cooling issues?

just throwing some ideas
do you know for sure you are getting water up to the thermostat housing? if you remove the one line (at the thermo housing) and briefly start the engine does water come out ? If you remove the line that connects to the manifold before it goes out the exhuast do you have water? when was the last time manifolds were changed? what size thermo stat did you put in? maybe its clogged at the power steering cooler prior to the engine,, the water tube inside the outdrive could have some crap in it also you need to see if you have water at the engine if so i would suspect the manifolds and risers need to be replaced but these are just guesses,,,,b/c Im just a backyard poor guy

 

[bkhitchens]

Re: 1994 OMC 5.0 Cooling issues?

Update: Checked hoses. Good flow from seawater pump to thermo housing. good flow from Circ. pump to thermo housing. Good flow from thermo housing to manifolds/risers. Put hose in circ. pump hose and had flow out of the thermo housing indicating to me that water is flowing unobstructed through block. Ran WOT - one gauge 140-150, one gauge 200 or more. No significant temp. differences on infrared thermo., both engines feel cool to touch while WOT. I just don't see any indication that engine is running hot other than gauge. Checked gauges and they are ok. Next step is temp. sending unit.