Thursday, December 28, 2017

Even the Losers
By Michael

Some of the bearings and shrapnel
that came out of my Yanmar.
Last fall, when I left Windy and the girls in Fiji to return to the States for the boat show in Annapolis and a visit with my folks in central California, I left them with a sick Yanmar. The raw water pump was on its way out, the interior walls corroded so badly that it was ripping up impellers and not allowing much water to be pushed. I called my Yanmar guy in San Diego and asked about a new pump.



“Yes…but, you can cut that in half by fitting the pump of another model on there—pumps the same volume of water—but you’ll have to order a specialized hose kit to make it work as the alternative pump input and output ports are in totally different locations.”

So I brought the alternative pump home with me, understanding that it would be a straightforward R&R.


I looked at the new pump from every angle, comparing it to the old. The gears lined up, the bolt holes matched. It looked good. The ports weren’t labeled, but I figured out the orientation based on the new hose kit and then confirmed. I was good to go.

If you’ve ever installed a backwards-facing raw water pump on a Yanmar with front-of-engine-only access, you can appreciate the challenge of this job. After removing the alternator to get in there, it’s working totally by feel and restricted to turning a couple nuts with a box wrench only about 20 degrees each go. All the while leaning forward at a difficult angle with only your forehead to support you. Typical boat work.

So I got the pump in and tightened her down and started the motor.

The pump squealed and made awful noises and the plate on the front of the engine, housing the bearing support, got really hot, really quick. I just knew I’d done something to mess up the gears and they were grinding themselves to bits. But lots of water shot out the back and then the noises stopped. And the plate cooled. And the water continued to shoot out the back.

Something had happened. Something was wrong. But all seemed good. Except for the slow leaking of water from the pump. With a flashlight I could see it drip, drip, drip. Obviously, the seals in this new pump were bad, or had been damaged by whatever had made that awful noise at start-up. But the water continued to gush out the exhaust like never before.

After a while, the oil pressure alarm began to faintly protest, not a full-blown alert, just a weak, sporadic buzz. I shut the engine down.

I got a good night’s sleep and resolved to taking it all apart again. To figure out what was going on.

The first thing I noticed in the morning is that the pan deep below the engine was filled with motor oil. I pumped out a few quarts.

At some point I realized that the dripping I’d assumed was water, had been oil. I felt for where the pump flange meets the engine and found a gap, and found that the pump was loose. It didn’t make sense. I’d tightened down the four mounting bolts as tightly as I could, now I could turn them by hand.

Here is the new pump fresh out of the engine,
with the inner bearing housing pressed on
(by me) to the hex nut.
I began taking everything apart. I started by removing the backing plate for the bearing support. Bearings and bits of ground-up metal fell out. This looked really bad. Then I realized what had happened.

This wasn’t a simple R&R. I should have noticed that the new pump wasn’t designed with a shaft intended to rest in a bearing support. In fact, the new pump had a hex nut on the end of the shaft that would be totally incompatible with any bearing support. For some reason, I’m dismissed this difference between the two pumps when I compared them.

I’d tightened up the new pump against the bearing support that prevented the pump flange from mating fully with the engine. When I started the engine, two things happened: oil leaked out the gap and the hex nut tore the bearing support to shreds.

The now-unnecessary bearing support.

Things were looking good. I reached into the housing to make sure I’d recovered all the bits and pieces, fortunately trapped and confined to that area. I removed the bearing race from the support. I reinstalled everything. I filled the engine up with oil.

All is good.

For all the nightmare scenarios that had been running through my head after hearing the noises, then to see the bearings and metal bits spill out of the engine, for this dumb error, I got off super easy.

As sung by the late, great Tom Petty (how I hate to write that), even the losers get lucky sometimes.

New pump and old, note on the old pump the smooth shaft intended
to rest in the bearing support. Note on the old, the hex nut beneath
the bearing inner race that is jammed onto it.

This is the bearing support housing plate that is bolted to the front
of the engine.

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