Do I have an overheating problem?

[nieuwkerk]

Last year, I purchased a very well maintained Columbia 31 and Atomic4. I love the boat and the engine!! However, this spring I noticed that temps quickly rose to 190 when running at 1200 RPM.

Suspecting the impellers, I changed both raw and fresh water impellers. The fresh water blades were very bent, and the raw water blades on the Sherwood pump were cracked and broken. Unfortunately, I did not do an inventory of parts at the time. However, later I checked the 90 degree angle fitting and the hoses, and there were no parts.

Last week, I ran the engine at 1500 RPM and the temperature was 185 degrees, and at 2000 RPM, it was about 195. These temps were observed in the Rappahonock river where the water temp was about 80-85 degrees. Also, the previous owner informed me the thermostat is "set" at 180 degrees.

I read in earlier posts that 190+ temps are a red flag. My question is: Should I expect the higher temps if the raw water is already warm - or is the raw water temp a non-factor and the problem is something else?

I'm planning bringing the boat up to Mystic Ct, and before I go, would like to know if I have a problem and what steps I should take to resolve the it.

Thanks in advance for the help,
Bill Nieuwkerk

[hanleyclifford]

Do you have a shut off valve in your bypass loop? If not, consider installing one.

[nieuwkerk]

I'm not sure. I'm a novice when it comes to engines. Here is a photo - What should I look for?

[hanleyclifford]

You have the late model with fresh water cooling, a nice looking installation. I cannot see, but the shut off valve would be concealed behind the salt water pump just under the thermostat housing, if it is a MMI kit. The valve is used to shut off the flow from the "T" on the side of the water jacket to the thermostat housing. The purpose is to "trump" any leakage inside the thermostat housing.

[nieuwkerk]

The boat is 4 hours away, so its difficult for me to check. However, I'm almost positive that I don't have one. I'm assuming MMI's Cooling system bypass kit (CSOT_01_61) is what you're referring to. If it is, I'll install it this weekend.

Just to be prepared, because I'm far from the boat, what else could it be if the bypass kit doesn't address the issue?

Thanks again for your help!

Bill

[Administrator]

What's this?

Bill

Update: I inadvertently deleted my subsequent posting, wondering whether this arrangement might result in air being sucked into the pump.

[nieuwkerk]

That hose goes to the galley's saltwater faucet in the sink. The previous owner had a (well-founded) aversion to creating holes in the boat!

[ArtJ]

I recently solved a overheating issue after replacing literally everything.
I had also flushed the salt water side and checked exhaust flow.
It turned on that the fresh water side was the issue Once flushing
the block out, the problem was solved and temperature range is
normal

[nieuwkerk]

Hmmmm. That never ocurred to me. I suppose you're right. Water always ran through the exhaust, I had no real baseline on how MUCH water should come out, so I never gave it a second thought.

There is a valve attached to the hose under the sink that I could close and test whether that resolves the issue.

I'll bet installing the bypass valve and closing the faucet valve will fix the problem (Hopefully) !!!!

As for the through-hull connection, it's bronze and has a shut-off valve and it seems correct. I'll double check this weekend.

I'll let you all know. Thanks,
Bill

[hanleyclifford]

Bill is right about that possible air leak in the intake side. It is a bad idea to make the engine share a thru hull with anything. I would plan to put another hole in the boat at next haul out.

[Baltimore Sailor]

Pardon my ignorance, but if he has freshwater cooling, isn't the actual cooling done by an antifreeze mix? What good would a bypass valve on the raw water line do in this case?

I assume that the raw water is used in a heat exchanger, since there's no way to use a fan to dissipate the heat, as with a car -- would the valve send more raw water into the exchanger to provide more cooling that way?

[hanleyclifford]

In all the systems I have seen the raw water flow thru it's side of the exchanger is constant. The antifreeze mix in the engine itself is controlled (hopefully, but not necessarily ) by the thermostat. What seems to happen is a destruction of the seat the thermostat needs to close the bypass. Hence the bypass shut off valve to, in effect, override the thermostat system.

[ArtJ]

Please get Don Moyers flushing procedure and his flushing kit .

You need to flush the system out piece by piece. There are
capped tubes ( or at least plugs) located on the alternator
side of the engine. You need to block them off as discussed in
the procedure and flush the engine block out piece by piece.