Uh Oh, Must Be Careful

Vero Beach
No LL

This weekend I did the long-term maintenance on our new engine for the first time after 850 hours of use. I changed the transmission oil, changed the secondary fuel filter, tightened the alternator belt, drained the primary coolant, cleaned the raw water strainer, and removed the heat exchanger tube stack for cleaning. I had been putting that off because I'm chicken to take things apart for the first time. I'm always afraid that I won't get it back together correctly.

The good news is that there was almost nothing to clean from the raw water strainer. Those things collect sticks and weeds, but mine was nearly clean.

When I removed the cap at the end of the heat exchanger, I was shocked to see two rubber bits sitting there. They were plainly the tips of the raw water pump impeller vanes. Uh Oh, that's bad. Even worse, the bits were on the opposite end of the heat exchanger from the pump, and the bits were much too large to fit through the tubes. It is a mystery to me how they got there.

Needless to say, I scrambled to take the raw water pump apart and remove the impeller. A picture of it is shown below. You can plainly see the broken vanes and the broken bits that I found separately. Fortunately, I had a spare impeller and I installed that.

Now for the lessons learned. The water flow seemed adequate and I never noticed any reduction in flow since the installation was new. I have no idea when the vanes broke. It is possible, even logical, that they broke the very first time I started the engine when the pump was completely dry, getting no lubrication from water. I guess the lesson to be learned is to keep spares on board, but more important, to take apart and inspect the pump impeller more frequently, perhaps every 100 hours.

Another shock. I felt the rubber exhaust hose. It is supposed to be very stiff and it is reinforced with internal wire. A section about one foot long was completely soft, and nearly collapsed. I discovered a long time ago that a bit of the hose rubbed against a bracket and had chafed a hole. I plugged the hole and put up chafing cloth to prevent recursion. I didn't think however about the bit of reinforcing wire exposed by the chafe. In the months between, about 18 inches of that wire had turned to rust inside the hose and made it soft. Tsk tsk, shame on me. Inspect inspect inspect all things that might go wrong and do it frequently. Also, just because things are brand new, does not mean that the inspection frequency can be reduced.