Old mechanical thoughts

At one time, my 7.5 Onan would eat raw water pump impellers like they were candy.
When I did not have a gasket for the pump I would make one out of the Nor'Easter cover page.
This was a monthly newspaper with heavy paper stock for the front and back page.
They worked as well as the real gaskets.
The pump used to loose prime easily.

Admiralty Charts also make very good gasket paper, If I have to ask for one to chop a bit out of I try to remove a bit that will not be used if the chart is needed such as the land mass.

On a delivery southbound one fall, I'd followed a 45ft Chris Craft sportfish, in and out, of course. We were making the same speed, and we got pretty well acquainted. He'd taken my card and the next spring he called me to return the boat to NY from Pompano for him since he was too busy. I figured the boat was in good shape, being active and all. He confirmed that it was running beautifully when I came aboard. Oh, just one thing, he said - the port engine, an 8-71TI, occasionally would snap the shaft on the raw water pump.

Whut?

Blow an impeller, yeah, but snap the shaft? He'd busted several, and had spares aboard, he bragged.

You shoulda seen the number of impeller blades I backflushed out of that heat exchanger. I guess they would all line up and cover all the tubing inside now and then. Can't compress water, ya know, so - -Blam! He'd paid some geniuses to unsuccessfully solve the problem. Well, this backflush is only costing you $100, I told him. . .so he slipped me a hondo.

I had a great 25kt ride to L. I. sound after that. Boogity boogity . . .

I was just sittin' here thinkin' about the yarn above, and remembered that same boat, the 45' CC, same trip the next spring. Big Jim was with me, as he was above also. Big was great company, and so powerful that a large pair of Vise-Grips would rust in his presence. We had a great springtime ride up the coast, ducking in for fuel now and then. We had to stop at Beaufort; couldn't miss that bar on the dock there, and a chance to hang out with Jeb.

We went inside up to Norfolk, planning to jump offshore there, but the weather turned downright ugly. I called the boss and mentioned that I could continue up the Chesapeake, adding about 85 miles to the ride. He was cool with that.

In the C&D Canal, I was pointing out the church in St. Georges where I'd happily married my loving wife, when Big said, "Why are we only doing 11 knots?" All the gauges were normal. Oh crap.

Big went below and stared at the shafts while I worked the clutches.

Confirmed. We'd lost a prop. How am I gonna explain this?

The nearest railway was Worton Creek. We hauled, pulled the shaft, and had a two-day wait for one to be machined in Baltimore and shipped. I hadn't hit anything - oh, I've bent a few props in my time, but this was not one of those times. But how to cover my butt?

A friend in Chestertown said that a Professor at Washington College was astute in metallurgy. We had him look at the shaft and the taper piece that I'd driven out of the prop. It had sheared right at the propeller hub. There was the corkscrew piece of steel sticking out, but the face of the shear had a highly-polished surface. That shaft had been cracked for quite a while, he said, and the vibration had "polished" the break's surfaces. He even gave me a written statement to that effect. Whew!!

The rest of the trip,mercifully, went OK. Oh yes - I found a prop in the lazzarette, under a canvas, that looked like a pretzel. And there was no yelling . . .

Big Jim is gone now, and I really miss him.

Moderators: Too Wordy?

Addendum to the above: We went back from Worton in another boat and dragged multiple pieces of chain in the Canal and actually snagged the prop and pulled it in OK. We got lucky. I was Worried!

Another addendum - -Geez
We did put that same prop back on the new shaft. And that hondo?
The fishing party boat captain that thought up the chain idea and took us to the canal got the hondo - easy come, easy go. . . .

I had that happen and it ended up to be a mostly blocked heat exchanger, but sometimes when the bearings are going on the raw water pump they eat up impellors also.

I like the use a thin coat of Permatex #2 on paper gaskets on both sides, it never hardens just gets gooey and works well at helping them seal and stay in place.