The big red tube-like thing is the heat exchanger. Cars have radiators, boats have heat exchangers. A car radiator uses a fan to blow air past the radiator, cooling the engine water that circulates through it. A heat exchanger on a boat pumps sea-water past the engine water to cool it. Same principle, denser medium. We have doubts about the efficiency of ours.
Last summer (when it was 80° on the bay) we overheated. There are a lot of possible causes. We changed the raw water pump impeller ("Commencement"). We cleaned the raw water strainer ("Valentine's Day"). Another possible cause is that the heat exchanger may be plugged with silt or scale. Perhaps we can clean the heat exchanger?
As Doug Z. says "It's just a chunk of iron, there has to be a way to out-think it." I can see why my sister loves him. We just need to out-think it. How hard can that be? Really?
(The little grey tube is the heat exchanger for the transmission. And there's also a heat exchanger for the oil.)
While we're not sailing much in the winter, it seemed look a good idea to find a way to clean the heat exchanger. I've read three procedures for attempting that.
Remove the end caps and use a 22 rifle cleaning rod to "rod out" the scale. This looks hard. The 6" space at each end the heat exchanger is too short for the 24" rod required.
Take it out and soak or boil it in acid. The acid folks vary from a few hours in vinegar to a few seconds with Muriatic acid. One blog post suggested dropping the whole unit into a container made of 6" PVC pipe with caps and sloshing it about. This looks easy.
Pump an acid like Apex Rydlyme through the system. This looks messy.
Taking it out seems like such a straightforward procedure. It's fastened to the engine with two hose clamps. It has four hoses—raw water in, raw water out, engine coolant in, engine coolant out—held on with hose clamps. Pretty simple, right?
It's just a chunk of iron. We've out-thought it. Right?
Step 1 is to pump the hazardous (and expensive) engine coolant out of the system. This involves disconnecting the water pump, inserting a hose, and pumping out a few gallons of 50/50 Prestone and water, and saving it for later.
Step 2 is to take off the four hose clamps. I decided to start with the hose clamp for coolant out, since that seemed the most accessible.
Hose clamp just popped off. Nice.
The hose, however, was immobile. It was—I noticed after a 15 minutes of struggle—painted onto the coolant input port. Painted on. Never been moved before. The only way to remove that piece of hose would be to cut it off with a hacksaw. (Marine hose is wire-reinforced so it won't collapse or kink; you can't cut it with a utility knife.)
Not Retreat — A Strategic Redeployment
Okay. Maybe I chose the wrong end of that hose. The other end is buried deep within the inaccessible parts of the engine. So, perhaps if I remove the other hose clamps and do the inaccessible one last instead of first.
Or let's just stop and think. It's just a chunk of iron. We're not defeated, we're merely adjusting the front.
If we were to switch to another tack and pump Rydlyme through the system, what would that involve?
Removing the raw-water pump's output hose. That's a hose clamp that are readily accessible. Indeed, I've already had my way with the raw water pump.
Removing the exhaust injector hose. Similarly, that's just another very accessible hose clamp.
Remove the zinc anode in the heat exchanger. Apparently, Rydlyme will dissolve the zinc just as aggressively as it dissolves the calcium scale.
We'll need a sacrificial pump. From what I've read, a pump that can withstand Rydlyme is expensive. A cheapo pump is probably less expensive than what the boatyard would charge me for a mechanic to hook up a good pump.
We'll need a couple of bronze hose-barb fittings. We can clamp the engine hoses to some into some extra hose that goes to the sacrificial pump.
We get a big old bucket and mix up Rydlyme and water in the recommended concentration.
We cycle the mixture around for a few hours.
We're not "defeated". We just didn't make as much progress as we had hoped.
The crew of Fawkes asked if we were running our engine room blower. Wait, what? Engine room blower?
The master plan is to hold off on this treatment. First, we need to see if the cleaned input strainer and new ductw0rk on the engine room blower offer enough improvement.