freshwater cooling

[glasply1]

My volvo engine, a chev 350, is showing leakage or corrosion on the fwc "tank." I'm sure that the fwc is original and the boat is a 1980 model. The boat is moored in saltwater and used exclusively in saltwater. One spot is on the starboard side of the tank where a hose is attached. There is some aqua blue material where the hose fits over the metal fitting. The other spot is on the port side of the fwc tank. The corrosion or whatever it is circles the large nut, about 1.5", where it screws into the end of the tank. The Volvo engine manual talks about maintenance but does not say how to deal with this situation. Can the nut at the end of the tank be safely removed, cleaned and replaced or should I take the whole thing off the engine and dismantle and clean it? I could just clean up the exterior corrosion and hit it with some spray paint? I would really like to do it right. SEARCH gave me 8 pages to check but none of the responses fit my situation. Comments and help appreciated.

 

[Haut Medoc]

Re: freshwater cooling

Not familiar with Volvo specifics, but if it is like most heat exchangers, that nut will come off & you will be looking at the raw water side of the system....<br />Replacing the gasket should fix that as well as letting you see what the core looks like....<br />I'ts made of brass so just knock the green oxide off & repaint.....JK

 

[Bondo]

Re: freshwater cooling

If it's an Original 1980,..........<br /><br />I'd consider removing the Whole Exchanger,+ having My local Radiator Shop give it the Once Over,........

 

[glasply1]

Re: freshwater cooling

Haut Medoc and Bondo: thank you both very much for your responses and suggestions. I kind of took a little from each of them. I took the whole assembly off and took it up to a marine engine parts store. Their estimate was $250 for a radiator shop to overhaul it and $500 + for a new San Juan Engineering replacement. Since the overheating (180-200 degrees at 3,000 - 3,200 rpm) was not excessive, I decided to see if I could clean it up myself and improve its functioning. By the way, the shop guy says that the increased cost of disposing of the hazardous materials for cleaning radiators has caused some shops to close their doors! Anyway, the North Seattle and Everett phone books did not show any radiator shops that worked on marine heat exchangers.<br />As I worked on the tank, four remnants of zincs came out of the elbow. A fifth would not come out because it was too long, so I left it in. It should erode on its own and I'll wait a month or so and add a new one with a new brass holder.<br />Since the remnants would have laid on the bottom of the tank and the outlet is on top, it seems that they probably would not be causing any trouble. <br />I soaked both the raw water and freshwater portions in cooling system cleaner and drained them. Didn't have much gunk come out. Maybe because I didn't have hot engine water to circulate in both halves.<br />Removing the bolt at the end of the raw water tank allowed me to check it somewhat. There were small crustaceans in there - not too many. Got most of it out. <br />Painted the tank, remounted it and ran the engine for awhile. Got it up to 140 degrees and so far no leaks. When our winds die down I'll take it out for a short cruise to test it again.<br />Long response! <br /><br />Thanks again to both of you for your help.

 

[Boomyal]

Re: freshwater cooling

Glaspply, now that you have the heat exchanger cleaned up, you need to install a 180 deg thermostat for your 350 SBC. 140/160 was only necessary for salt water cooling. It was a compromise for the purpose of keeping salt from plating out in the engine block.<br /><br />You don't have that problem and engines run much more efficiently with a 180 deg coolant temperature.

 

[glasply1]

Re: freshwater cooling

I think I do have a 180 degree or so thermostat. The temp only went up to 140 because I was still at my mooring, and not running the engine too fast. It will get a chance to go higher when I take it out for a test ride this week. Thanks for the suggestion. I will keep the thermostat in mind.

 

[Haut Medoc]

Re: freshwater cooling

There ia a radiator shop on Lake City Way & N. 80th or so....<br />He will hot tank & rod out a marine exachanger for $80.00 or so ....JK

 

[glasply1]

Re: freshwater cooling

The radiator shop you referred to sent me to one in the Greenwood area. He wanted to take a look at the heat exchanger before agreeing to work on it. <br />The first test ride after I cleaned it was ok until one of the hoses came off. Put it back on later and went for another ride where it went up to 160 degrees and no higher, although I didn't go over 3200 rpm. On the next quiet day on Puget Sound I will run it up to the max and see what happens.<br />When I replaced the zinc in the heat exchanger I put a little marine grease on the zinc's threads since the last one was difficult to remove. Will the grease affect the usefulness of the zinc? Does it have to be making perfect contact with the brass nut holding it into the tank?