Monday, July 23, 2007

Learning about engine cooling

About a month ago, I finally learned a lot about how Meridian's engines are cooled. The way I learned is pretty typical of how I learn anything new about that boat.

You see, I didn't start out trying to learn about the cooling system. My plan was to clean up the port engine a bit in order to locate an oil leak.

But once I thought about it, I decided I should also paint the entire engine and exhaust manifolds. After all, they were beginning to rust, and that rust was starting to accelerate.

Here's a photo of the port engine, prior to cleaning. As you can see, there's nice easy access all around it.

So I started out by cleaning up and painting the front of the engine. I removed all the hoses and belts, as well as the sea water pump, circulating water pump pulley cover, and alternator. I cleaned those up as well as the surrounding engine block, then taped (and newspapered) over the stuff that shouldn't be painted, and finally painted the front section of the engine. I then put everything back together. It looked great.

Now, in the middle of all this, while parts were strewn all over the engine room, Bernie popped her head through the hatch, took one look at the scene, and gave me one of those "Oh boy, here he goes again" looks. Attempting to head off the certain "are you sure you know what you're doing" comment that I knew was on its way, I said in my most confident sounding voice "Hey, you know the great thing about having two engines? If you aren't sure about how to put something back together, you can just take a look at the other engine."

It seemed to work, because she nodded "uh huh" and left.

Armed with my engine manual that shows exploding parts diagrams, and confident that I also had access, if necessary, to an internet full of information about these engines, I forged onward.

Then, after completing the job, I took a minute to bask in the pride of accomplishment.

I eventually started the engine just to ensure everything was well. I was primarily checking for water leaks after having removed and reinstalled all the hoses. What I found was, well, pretty much the opposite of a leak. No water was coming out of the boat's exhaust pipe.

Now, water from the exhaust is one of those "must have" items. If no water is coming out, that means water isn't flowing through and cooling the engine, and that means it will overheat. Fast.

So I shut off the engine and started looking for the problem.

Over the course of the next two days, I used all those exploding parts diagrams in the manual, as well as a good chunk of that internet information, while trying to diagnose the problem. I learned how and where water flows through the system, where the pressure valves and thermostats are, how to check a thermostat, where blockages can occur, and, basically, how it all fits together and works.

It was a frustrating two days though, because I still wasn't getting water to flow through. I had convinced myself that there was a blockage or air pocket I had created when removing the hoses and watching the water drain out.

About the middle of the second day, I decided to be more systematic about it. I started at the very beginning - the water intake on the bottom of the hull - by diving under the boat to see if a plastic bag or something had clogged the intake. I then moved to the sea cock, and made sure water was flowing through it. I then moved to the water pump to make sure water was reaching it. Next I moved to the water pump outflow - and found no water was leaving the water pump.

At first that didn't make sense because I knew the pump was working just fine. I had changed the impeller, and had even switched it with the pump on the other engine.

That's when the "Phil you're an idiot" lightbulb went off. Ten minutes later the problem was solved.

You see, the engines are clearly marked "right hand" and "left hand" rotation. That means they rotate in different directions. Once I cranked the starboard engine and watched the belts operate in the opposite direction from those on the port engine, I really regretted that comment I made to Bernie about "the great thing about having two engines . . ."

But I have to admit, I'd never have learned so much about the cooling system IF I HADN'T MOUNTED THE WATER PUMP UPSIDE DOWN.

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