Fresh Water Cooling System

[buzzeroo]

I'm in the process of a complete in-the-boat engine refurb due to a stuck #4 exhaust valve. The (late model) engine was fitted with FWC'ing some years ago by the original owner using the SenDure FWC kit. As a result the internal cooling passages are good as new. Before the tear down, the temp would creep to about 190 at cruise, but never hotter. Good raw water pulses from the exhaust; I assumed all was well. Not so.

Now that I have everything apart, I've discovered the following:

* No thermostat was installed.
* The original factory diverter cap is in place.
* The hose between the diverter fitting and thermostat housing had been removed and plugged.
* The coolant tubes on the raw water side of the heat exchanger were almost completely clogged with years of accumulated sea water crud.

My theory is that a previous owner (I'm the fourth) removed the thermostat to compensate for a slowly clogging heat exchanger. The schematic for the FWC kit installation does not show the hose connection between the diverter fitting and thermostat housing.

So I have a few questions:

* What is the recommended acid solution for soaking/cleaning the crud out of the heat exchanger.
* Is a 180 degree thermostat available that does not require the thermostat housing spacer kit.
* Should the hose connection between the diverter fitting and thermostat housing be re-installed.
* Would a new diverter cap make a significant difference.

On another note, I am now a "true believer" regarding closing the raw water intake before starting the engine and again just before stopping it. Not only was #4 exhaust stuck from exhaust raw water intrusion, it looked like a rusty mushroom. And, even more fun, #4 piston was seized to the cylinder wall. A liberal soaking in B'laster (great stuff) and MMO for two weeks, plus a 24" pipe wrench got everything moving again.

Regards,

Buzz Williams

[Don Moyer]

Buzz,

Here are my thoughts on your questions:

What is the recommended acid solution for soaking/cleaning the crud out of the heat exchanger?

If the build-up is mostly a calcified material, you may have to use full strength household muriatic acid, which is currently a 30% concentration.

Or, you could take it to an automobile radiator shop and have them deal with it. I've taken a couple heat exchangers to a local radiator shop and whatever they were using in their hot tank worked great.

Is a 180 degree thermostat available that does not require the thermostat housing spacer kit?

Yes, Westerbeke makes their OEM 140 degree thermostat in a 180 degree version, but we removed it from our catalog some years ago.

Except in very cool outside water temperature (50 degrees or so), engine temperatures routinely run 20 to 30 degrees hotter than the advertised specifications of the thermostat in late model engines, due to the characteristics of bypass cooling systems; e.g., 140 degree thermostats frequently maintain approximately 160 to 170 degrees. Accordingly, 180 degree thermostats frequently allow temperatures in the 200 degree range,
which is a bit high.

Should the hose connection between the diverter fitting and thermostat housing be re-installed, and would a new diverter cap make a significant difference?

Unless outside water temperature dips down to the range of 50 degrees, the capacity of all freshwater cooling kits will maintain 170 to 185 degrees with brief periods of 190 in hot shallow creeks under high power settings, even with no thermostat and the bypass hose blocked off.

The problem is that, with no thermostat, it takes quite a while to equilibrate at these temperatures. Therefore, our preference is for a 140 degree thermostat in the factory configuration (diverter cap and all) which will usually get the temperature to a normal operating range of 160 or so in a timely manner, and then let the temperature slowly equilibrate to its eventual range, which might be 180 or so in a fresh water cooled engine in most of our operating areas.

NOTE: It has also been a characteristic of both 140 and 180 OEM thermostats to sometimes stick partially open. My personal suspicion is that if you have a 180 degree thermostat that appears to be working, it's because it's stuck in a partially open position. There's not a thing wrong with continuing in that manner; we simply couldn't continue selling these units, hoping they would fail in a way which would provide acceptable temperature control.

Don

[buzzeroo]

Thanks, Don. I'm going to put it all back together in the factory configuration using your aftermarket thermostat kit. I'll let you know how it cools.

Buzz Williams