Overheating Issue

[BlueWhale]

Hello Everyone,

I could use some help with my overheating issue. Let me give you the full context of the problem and what I've done to try to remedy the situation. Perhaps the collective intelligence of the wonderful folk here can save me some time and frustration. Here goes: Last spring I replaced my water jacket cover adding the brass cap and drilling the diversions hole as directed. Everything ran fine throughout the summer. I took several long cruises with no wind and plenty of motoring. Everything worked fine. Later in the season, admittedly after too much disuse, I began to notice on a few short sails that the temperature was running above my normal 140 - 160. Since, I was only going on short sails and only needed the engine to get me in and out of the slip (I cut the engine ASAP) and off I went, until conditions required me to use the engine under heavy load one night. Needless to say she overheated just as i was approaching my marina requiring me to make an emergency stop at the marina next door. I got a tow over to my slip and hoped i hadn't done major damage to my engine as she wouldn't restart after cooling. When I got a chance to get back to the marina a week or so later she started right away but continued to run hot. So, my first thoughts were something was stuck in the intake. I checked the through hull and cleaned out the strainer. I even had the bottom dived on and cleaned. No success. Since I hadn't changed the impeller in a couple of years I next replaced the impeller. It was fouled. The rubber part had separated from the inner ring and was no longer rotating in the pump. Still no success. Next, I replaced the thermostat. I gave the old one a vinegar bath and tested it in a pot of hot water. It was stuck in the open position (down). When the temperature of the water in the pot rose the underside of the thermostat did not rise. So, I bought a new one and figured that would be it and I would be sailing down the Patapsco River very soon. Well, when I installed the new thermostat on Saturday it still overheated - UGH!!! It was suggested that I work my way down the back end of the cooling system checking hoses for crude, corrosion and clogs. That's next on my agenda. I'm somewhat confused on exactly how the cooling system flows. I know when the temperature reaches 140 degrees the thermostat opens to allow water to pass through to cool the engine? How is it diverted when it is closed? In my situation water passes through the system fine until it has to move through the engine. I'm figuring that there is a blockage in that portion of the cooling system. What is the most common place and cause of such an issue? Is my reasoning sound or is there something in my understanding of how the cooling system operates inaccurate? Is it possible that something is going on with the water jacket replacement from the spring (I surely hope not). I'll be removing hoses and elbow joints in the coming days and checking for blockages. Any advice on this matter would be tremendously appreciated. I really need my sailing therapy!

Thanks

Brian
S/V Rekofa The Blue Whale
1979 C&C34

[Marian Claire]

Welcome to the forum.
Is the amount of water exiting the exhaust the same as before the overheating issue? Was the impeller intact, other than the separation, when you removed it? Any missing fins?
A description of your cooling system may be helpful. Late model? Bypass?
The process of going connection to connection and checking for flow is the best way to locate the problem area. Start from either end and work thru the whole system.
Dan S/V Marian Claire

[BadaBing]

Hi Brian.
Welcome
As asked. Are you sure that the old.impeller did not send a pc of itself into a hose a clog up the flow. The first natural place for such a jam it the T fitting at the water jacket plate.

Are you fresh or raw water cooled?
Did you try running it with no thermostat?

A picture of your engine and thermostat set up might help.

When is the last time you flushed the engine, acid? vinager? Back flush of manifold and block?

To test your flow I suggest, working with a cold engine, you disconnect the hose conning out.of the thermostat housing. This hose should go from the thermostat housing to the exhaust manifold.

Connect a pc of hose to the out flow connection on the thermostats housing with the other end going into a 5 gal. bucket. Have someone hold it in the empty bucket and start the engine. At idle somewhere between 3-4 gallons of water should pump through the block and.or bypass in 1 minute of running.
If you have that.much flow than the problem probably is after the thermostat.

Now reconnect the hose and do the same experiment With the discharge out of the exhaust manifold. You should get the same amount of water in your test bucket after a 1 minute run at idle, 3-4 gpm.

If you do not have this much water first check your hoses. An overheat can cause the inner wall of hoses to collapse. If the hoses are good, and assuming you have good flow.through the engine, it could be a blockage in the manifold, a common problem. If you have good flow through the engine and the.manifold and you know the hoses are sound then it very possible.that you have developed.a.blockage in the hot section of the exhaust pipe, or the waterlogged muffler (or standalone depending on which you have)

[BlueWhale]

Welcome to the forum.
Is the amount of water exiting the exhaust the same as before the overheating issue? Was the impeller intact, other than the separation, when you removed it? Any missing fins?
A description of your cooling system may be helpful. Late model? Bypass?
The process of going connection to connection and checking for flow is the best way to locate the problem area. Start from either end and work thru the whole system.
Dan S/V Marian Claire

Yes, the same amount of water is exiting. Yes, the impeller was intact. No missing find. Late model cooling system. No bypass.

[BlueWhale]

Hi Brian.
Welcome
As asked. Are you sure that the old.impeller did not send a pc of itself into a hose a clog up the flow. The first natural place for such a jam it the T fitting at the water jacket plate.

Are you fresh or raw water cooled?
Did you try running it with no thermostat?

A picture of your engine and thermostat set up might help.

When is the last time you flushed the engine, acid? vinager? Back flush of manifold and block?

To test your flow I suggest, working with a cold engine, you disconnect the hose conning out.of the thermostat housing. This hose should go from the thermostat housing to the exhaust manifold.

Connect a pc of hose to the out flow connection on the thermostats housing with the other end going into a 5 gal. bucket. Have someone hold it in the empty bucket and start the engine. At idle somewhere between 3-4 gallons of water should pump through the block and.or bypass in 1 minute of running.
If you have that.much flow than the problem probably is after the thermostat.

Now reconnect the hose and do the same experiment With the discharge out of the exhaust manifold. You should get the same amount of water in your test bucket after a 1 minute run at idle, 3-4 gpm.

If you do not have this much water first check your hoses. An overheat can cause the inner wall of hoses to collapse. If the hoses are good, and assuming you have good flow.through the engine, it could be a blockage in the manifold, a common problem. If you have good flow through the engine and the.manifold and you know the hoses are sound then it very possible.that you have developed.a.blockage in the hot section of the exhaust pipe, or the waterlogged muffler (or standalone depending on which you have)

The impeller was intact with no missing fins. The system is raw water cooled. Did not try without the thermostat. Have had the boat 4+ years and have never flushed. Thanks for the description of how to diagnose where the blockage may be. I'll let you know the results.

I'm hopeful

[Easy Rider]

Brian,

A common blockage site for a RWC A4 is at the location of the brass 90 outlet elbow located on the top of the manifold. I would suggest you remove the elbow and check the threaded hole in the manifold for any krap buildup. Its surprising how over time crud build up can accumulate in this spot. Since you started overheating have you noticed any steam or even an increase in steam coming out the exhaust outlet at the transom? That could be another clue.

Chuck

[Al Schober]

Brian,
Hello, and welcome to the forum.
First thing I'd do is to take out the thermostat. They do go bad - you can test yours and reinstall later if you want. Get the engine running cool first - warm it up later.
Most common spot for blockage in a raw water system is the outlet of the manifold. Clearing it requires removing the hose and the fitting. But, the blockage can be anywhere. Anything from a dead fish in the inlet valve to impeller blades in pipe fittings. If in doubt, disconnect it and blow through it - if your cheeks puff out, you've found the blockage.
The blocks will clog internally. The internal passages over by the valves going from the block to the head are notorious. Flushing with acid won't clean the passages - only way is to remove the head and go at it with 'implements of destruction'.
But do the easy stuff first - remove the thermostat and clear blockages in the plumbing.

[JOHN COOKSON]

Yes, the same amount of water is exiting. Yes, the impeller was intact. No missing find. Late model cooling system. No bypass ???.

The late model engine will have a hose from the water pump to the T fitting on the side plate. And another hose from the T fitting to the thermostat housing. This is the "bypass" hose.* It allows water to flow around the engine rather than through the engine for a quicker warm up. When the double action thermostat opens it blocks the bypass at the top of the thermostat housing and the water is forced through the engine. Sometimes the seal inside the housing is imperfect due to corrosion and when the thermostat opens the bypass is not blocked and water flows around the engine by way of the bypass. Having a build up of crud in the engine water passages over the years will will make this situation much worse.
So anyway another thing to try is clamping the bypass hose when the engine starts to over heat. This will force all the cooling water to through the engine not around the engine bypass. If this doesn't help ditch the thermostat and try clamping the bypass again.
I can tell you for sure that in a RWC engine that if you have enough water flowing through the engine (not around the engine through the bypass) your engine will not run hot.

TRUE GRIT

* If your plumbing is any different than this let us know. We will also need a picture or two.

[Marian Claire]

Might be helpful. http://www.moyermarine.com/forums/showthread.php?t=4267

Dan S/V Marian Claire

[Ajax]

I would definitely remove the thermostat. It actually sounds like it's stuck shut, not open. Mine failed this past season as well.

Also, you said the engine was used only a little. Do you have krap growing over your seawater intake on the exterior of the hull? Perhaps it needs a cleaning.
If I don't sail enough, I need to ream out my seawater through-hull to clear the growth.

[Marian Claire]

"Single-action thermostats also require a method of controlling the flow within the bypass loop in order to provide the necessary flow through the block and head to enable the thermostat to regulate temperature within normal range. If you do not already have a valve in your bypass loop, you can find one in our online catalog with a product number of CSOT_01_61. "
From the online catalog.

What T-stat did you install?
If you used the T from MMI you must have a bypass unless you just plugged one side of the T. Check and make sure you do not have a bypass as stated in post #4. If you do have the bypass and it does not have a valve that could be your issue.
When cold the T-stat is closed. With out a restriction in the bypass all water goes thru the bypass and passes over the T-stat. This may keep the T-stat cold and it never begins to open. The engine gets hot even though you have full flow out the exhaust because no or very little water is passing thru the block.
I would try the suggestion in post #8 and close/restrict the bypass.

Dan S/V Marian Claire

[joe_db]

Back when I was RWC, I had a fish get in the intake line and I had marine life of some kind clog the thermostat*. I also had a gradual buildup of minerals that would increase the operating temps until I acid flushed the engine. I would undertake a thorough poke, prod, and flush at all available connections. You can run a hose in one end of the manifold and out the other. You might want do it backwards to unwedge pieces of crap that are stuck. Likewise you can plug the bypass, remove the thermostat, and flush forwards and backwards. Remember the pump is an obstacle, you need to unhook it for flushing. Removing the thermostat and putting a valve in the bypass loop is another good thing to try and some people just do this permanently.
Long term - get an intake strainer and a heat exchanger. If my heat exchanger gets clogged I can just unbolt it and take it home to boil out.

* this was not a fun day. The engine would overheat badly if run over idle. I decided to remove the thermostat and the water that was trapped in the engine was around 240 degrees or so. As soon as it had an opening it flashed to steam and sprayed me with scalding hot steam and water that smelled like dead fish It took some doing to get the smell off me! my buddy on the helm made all kinds of comments as to what I was doing to be running around the cabin cussing and smelling like that LOL.

[hanleyclifford]

There is a reason Moyer Marine sells this bronze replacement:

[BlueWhale]

Brian,

A common blockage site for a RWC A4 is at the location of the brass 90 outlet elbow located on the top of the manifold. I would suggest you remove the elbow and check the threaded hole in the manifold for any krap buildup. Its surprising how over time crud build up can accumulate in this spot. Since you started overheating have you noticed any steam or even an increase in steam coming out the exhaust outlet at the transom? That could be another clue.

Chuck

Water flows through the system fine until the temperature rises and the thermostat closes off diverting the water into the engine. It seems that the blockage is either in the engine itself. Perhaps the bypass hose is bad and collapses when the temperature rises? I'll be on the boat in the morning and check it out.

I do get steam, but only after the temperature begins to rise. At that point there is no water flow either.

Thanks

[BlueWhale]

Brian,
Hello, and welcome to the forum.
First thing I'd do is to take out the thermostat. They do go bad - you can test yours and reinstall later if you want. Get the engine running cool first - warm it up later.
Most common spot for blockage in a raw water system is the outlet of the manifold. Clearing it requires removing the hose and the fitting. But, the blockage can be anywhere. Anything from a dead fish in the inlet valve to impeller blades in pipe fittings. If in doubt, disconnect it and blow through it - if your cheeks puff out, you've found the blockage.
The blocks will clog internally. The internal passages over by the valves going from the block to the head are notorious. Flushing with acid won't clean the passages - only way is to remove the head and go at it with 'implements of destruction'.
But do the easy stuff first - remove the thermostat and clear blockages in the plumbing.

I'm hoping the issue is not internal.

We'll see.