470 cooling yet again

[2fishy4u]

Hello all, if you have watched my posts. You know i have the worst luck with engines. This time around, port was slightly overheating at anything over 1500 rpms. The exhaust manifold turned out to be leaking exhaust into coolant. So I replaced the exhaust. And guess what, nothing changed..... So far, new heat exchanger, thermastat, hoses, exhaust manifold, new riser, plugs, wires, rebuilt carb, reset timing, replaced impeller. I swapped drive hoses and starboard still holds it temp running off the port drive, and the port still heats up running off the starboard drive. Oil and coolant are clean. Flushed the engine side and plenty of flow. Anyone got an idea what could be up this time? Is it possible for maybe a headgasket failure that is letting exhaust into coolant without contaminating the oil or coolant? Pressure tested for a cracked block, no leaks. I am lost, and so is the mechanic. Nothing like spending a few grand and still have the issue. I said I was going to sell this thing, but I have not had both engines running for 3 months now.

 

[alldodge]

Been reading thru your other post and will say you have had a lot of problems but your also bouncing around. Your other thread on this subject would be the best place to add this comment. Your still talking about the port motor and others have been commenting.

http://forums.iboats.com/forum/engi...ngines-outdrives/10411192-470-the-death-of-me

To start another thread about the same subject might get someone new to look but can also cause the others that were helping to pass. I try to look at all threads but try to stay clear of 470's because I have messed up a few times.

To your continuing issue:
From my understanding I think your motor is overheating because there is not enough heat transfer. This is being caused by either not enough water being pumped and/or moved thru the HE, or your circulating water pump is not moving the coolant.

I don't think its from the drive because you said the starboard drive was cooling the port and vice versa and the port still overheated. So this leaves restrictions in the HE, the block or thermostat housing, or the circulating pump. There could also be an issue with restrictions on the coolant side of the HE. To rule out the HE swap them

 

[2fishy4u]

Thanks alldodge you have given me sound advice in the past, Yeah I figured the last issue was solved with the exhaust manifold It was beyond corroded, and bubbles were coming out of one of the bolts. So didnt think to post back there since I claimed it was solved. The heat exchanger is completely clear. I have extra everything for this boat, so its easy to swap things around. I pull the old part put in the new one, then rebuild the old one if it can be. I even have an extra reman engine siting in the garage I got from a business closing its doors and gave me the engine for 500$ mounts and all. I have found many insane deals on ebay so I keep buying parts I dont need. But may some day need lol. extra drive, covers, gaskets, belts, pumps, my wife complains about the space in the garage shrinking lol. This engine is a reman put in a year and a half ago. So I was not surprised that nothing came out during the engine flush. As buildup is usually over many years. Over the last year and a half everything on the outside of the engine has now been replace besides the intake. And after what you just wrote, I was assuming the circulating pump would not be an issue since this is a reman. Then I remembered reading, they tend to use the old pump when doing a reman if it looks good. So, it may be an original 80's part. It makes since to be in the closed system since the rest seam to function proper. And with a new manifold the thermostat housing was obviously clear. So I am down to circulation pump, or blockage in the block somehow. The circulation pump is a pull engine job? Its basically the same job as the weep hole leak fix that is posted on here? (Yeah I did that on the starboard a couple years ago lol)

 

[alldodge]

Pull the hose off the circulating pump and look up inside it. Rotate it to see if all the vanes look good, then grab one of the vanes with pliers and see if you can turn the pulley.

My thought on the HE is on the coolant side, not the raw water side. I could be there is build up around the tubes that can not be seen by looking down into the HE (radiator) cap

 

[kenny nunez]

I was a Mercruiser dealer from 76-03. Any time a 470 came in with a heating problem and everything checked out it turned out to be a leaking head gasket. After pulling the head and inspecting the gasket we could never see a place where the leak was. Even the machine shop that would resurface the head could never see a leak spot. The way the engine is made there is no lateral support for the cylinders and they do tend to move ever so slightly and that is how the leak starts. Years ago Cadilac had an engine that would do the same thing.

 

[2fishy4u]

Well, checked the circulating pump, it felt fine and tight. Refilled with coolant, and fired it up. after about 5 minutes and before it was at full temp it started smoking a lot out the back with a very heavy coolant smell. So there is now coolant getting into the cylinder.......... slight Trace of coolant now showing in oil. So it looks like it was the beginnings of a head gasket going out.

 

[alldodge]

Sorry to hear it but good to know what it was, and Kenny nailed it