Looks like the leak­ing gland is a score draw

Canal Boat - - Back Cabin: Experts -

Q Half­way along the re­turn leg of a 50-minute each way trip, I stopped to check the stern gland. It was un­com­fort­ably hot and there was no wa­ter in the catch tin sus­pended below the shaft/gland. By the time I got back to the ma­rina, about 25 min­utes later, the tin was over­flow­ing and there was wa­ter on the base­plate.

I re­cently re­placed the nuts on the clamp­ing screws with Ny­loc lock nuts since the brass nuts and slim lock­nuts ap­peared to work loose oc­ca­sion­ally. I ran the engine to­day in gear un­til the gland was only just warm with­out see­ing any drips, the lock­nuts were tight and the shaft could be freely turned by hand when disconnected from the drive.

It’s been sug­gested that a groove in the shaft is caus­ing the leak, and one method of over­com­ing this is to pull the shaft into the cou­pling by 5/16in so the new pack­ing is on a new sec­tion. I’m not sure l have that much play be­tween the end of the shaft and the face of the flex­i­ble mem­brane of the cou­pling. The other alternative is to pull the shaft out by 5/16in and then repack.

How can the gland can be wa­ter­tight for 75 min­utes and then sud­denly al­low in ex­cess of a pint of wa­ter to pass?

JOHN LIT­TLE, via email

A TONY REPLIES… First thoughts are that ei­ther the gland was over­tight so it over­heated, or the shaft is out of align­ment (es­pe­cially if your flex­i­ble engine mounts are more than a few years old). The fact that the nuts plus lock­nuts worked loose in­di­cates ex­cess vi­bra­tion which again sug­gests an align­ment prob­lem, a bent shaft or dam­aged/fouled pro­pel­ler.

Most boats need their glands ad­justed each year or so. When tight­en­ing the gland you should be able to turn the cou­pling by hand when in neu­tral but with some re­sis­tance. If this were an align­ment prob­lem, the shaft would have dropped back in line when you disconnected the cou­pling.

If by ‘work loose’ you mean the nuts were still locked to­gether but the gland needed tight­en­ing more than once a year, that sug­gests shaft mis­align­ment, wear in the shaft, or that the stern gland cast­ings are worn by run­ning out of align­ment.

Flex­i­bly mounted en­gines move for­ward on their mounts when ahead is en­gaged and back­wards for astern. This pushes and pulls the shaft through the pack­ing so a groove in the shaft would chew the pack­ing up and could cause jam­ming (hence the heat) or leak­ing. If you re­move the pack­ing you can usu­ally feel a groove in the shaft us­ing a length of wire coathanger with a right-an­gled bend (pic­tured). Wa­ter will leak in with the pack­ing re­moved, but the bilge pump should more than cope.

If the prop is far enough away from the stern­post, mov­ing a grooved shaft for­ward a small amount will help make a seal. How­ever, the pack­ing prob­a­bly covers be­tween a half and three quar­ters of an inch of shaft so some of the groove will still be un­der the pack­ing. In that case, as the engine moves it may still dam­age the pack­ing. It is prob­a­bly an ef­fec­tive tem­po­rary so­lu­tion but might not last.

You may have over tight­ened it and pos­si­bly moved the pack­ing so now it could have set­tled down. I would give it an­other test run of an hour or more but keep check­ing for over­heat­ing. It can be warm but never hot.

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