The only thing that was disappointing about our Annapolis trip was our inability to take the boat on plain. It did not hamper us in any way, but it would have been nice to know that we could take it up to 25 knots if needed. Time to take care of the over-heating problem once and for all.
We noticed that one of the risers on the starboard engine felt much hotter to the touch than the other riser, so we decided to take it off and have a look. We ordered a new gasket from West Marine and it had just arrived, so we headed down to the marina to get our hands dirty.
It was not difficult to remove the riser. Just 4 bolts and a hose clamp and it came right off. Upon inspection, it looked fine, but we decided to soak it in muriatic acid overnight to see what would happen. I lot of bubbling, so we were hopeful.
We installed it the next day and took her for a test run. No luck. Same over-heating problem, perhaps a tiny bit better. This left us with one more option – the dreaded oil cooler. Not that the cooler is hard to remove – just a couple of bolts and hose clamps. The problem is getting to it on our boat. The starboard side of the engine compartment is very small. Getting into the area should be fine, getting out had us a little worried. Then it dawned on me: the oil cooler was mounted vertically on the engine, with the hoses connected at the top. If I removed the hoses, and hooked up longer ones, I could use a funnel to pure the acid into the cooler without removing it from the engine.
We picked up a couple of 1 ¼ hoses at Lowes, another couple gallons of acid and a bucket to collect the acid after it ran through the cooler. We pulled out the zinc plug at the bottom of the cooler to let whatever water was in it run out. The zinc was completely depleted – a possible clue. We put the plug back in and then ran about half a gallon of acid through the hose on the inlet side, until it came out of the hose on the outlet side, and into the bucket. We let the acid sit ion the cooler for about a half hour, then ran water through the hoses to see what would come out.
The bucket filled with black, sooty water. Finally, a sign that we might have found the problem! We repeated the above process 2 more times, until the water going into the bucket looked clean. We then re-installed the original hoses and took the boat out for a test.
Perfect! The temperature stayed at a steady 160 degrees, even when we took it on plain at 3300 rpms. It was now running even cooler than the port engine by 5 degrees. It looks like we will be cleaning the port oil cooler some time soon!