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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
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