Looks like the leaking gland is a score draw
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.