Prop Shaft Seal 101?

Need some help understanding what I have for seals on my 1998 Mainship 35’ trawler, and what condition it is in. I’m a newbie to drive shaft seals and their adjustments. I have read some posts that discuss water hoses going to them and tightening the packing nut but not sure that applies to this style. PO told me to tighten it if they leak too much. What to tighten and what’s too much? Usually start with a dry bilge and after a 2-3 hour cruise there is 1-2 gallons in bilge when return. I’m concerned with the corrosion on the aft clamps and the condition of the rubber hose. I’m assuming a haul out for replacement. Any help or suggestions are appreciated.

That’s a traditional packing gland, IMO far superior to “dripless” style when loaded with Teflon impregnated packing properly cut and inserted with plenty of Teflon grease.
If the rubber tube and clamps look flaky, replace them, no telling how long they’ve been there!
Replacing the rubber tube will necessitate splitting the coupling and removing the back half.
I’ve done this in the water, it’ll leak some, but you can slow it down considerably by wrapping the shaft where it emerges with Saran Wrap and/or inner tube strips.
Google replace shaft packing, there’s tons of info out there.

Plus you have the type with 2 bolts to draw in the outer part when tightening, instead of the 2 big nuts type which seize and are hard to grip and turn.
Is that a water feed aft, if so you may be able to adjust a little harder if needs be.
The work you have in mind might be better done first time around during a haulout.

Yes that is the best style of shaft packing gland.

Use Duramax or similar , a modern product , you will adjust it once and it will not drip a drop or overheat .


Duramax Shaft Sealing Systems: Ultra-X High-Performance Packing


www.duramaxmarine.com/shaft-ultrax.htm

Steve D'Antonio has a good article about stuffing boxes. It is worth the read.



https://stevedmarineconsulting.com/...conventional-stuffing-boxes/?upm_export=print


Ken

Plus 1 Duramax. One and done!

With a 1998 boat, you most likely have the teflon packing in place. That can be checked by loosening off the fwd adjustable part and sliding it out of the way, then check the colour of the packing. Teflon will show white, non-teflon will not. Then tighten till you don't get any drips at rest, run the engine, in gear, and tighten till the dripping just stops. Redo after a few hours running, and again. Then you only need to replace if you can't get it to stop dripping, or if you are compelled to know that yours is new. Once satisfied, check it at least annually. Should be good for many years.

Thanks everyone for the info and the links, will spend more in-depth read when I can. I’ll add the hose replacement to the list for haul-out in the spring and play around with the tightening as suggested. Love working upside down in the bilge.

BruceK said:

Is that a water feed aft, if so you may be able to adjust a little harder if needs be.t.

Click to expand...

I thought the same thing, but zoomed in the pic and it is a bonding wire!
I like to have a water feed, it helps keep the bearing cool and clean, and since I always flush with fresh water following use, the stern tube and bearing get the salt cleaned out and will be parked in fresh water, limiting marine growth.

Is that a plastic pipe plug? If so replace with SS or bronze.
Also very important to keep the gland even when tightening. Maybe it’s just the picture but the gland looks a little cocked.

GFO marine packing, it is great packing. Mine has lasted so far more than a decade without wearing or leaking at all. Runs cool, very slippery, soft packing.

It has been truly pack it and forget it for me. The old style flax packing is junk, it will leak, score shafts, wear out, and cause you to work harder and spend more money than you should like buying some expensive rubber boot bellows that can rot and ceramic ring device that has to be burped or it overheats and breaks.

High Wire said:

Is that a plastic pipe plug? If so replace with SS or bronze.
Also very important to keep the gland even when tightening. Maybe it’s just the picture but the gland looks a little cocked.

Click to expand...

Looks like my starboard side when I bought the boat. To my eye, way out of whack on the starboard side of the flange which appears to be nowhere as tight as the port. I was told to back both sides all the way out and retighten using equal turns on both bolts. Tightened until the drips stopped when not running.
Then went through the tightening process outlined above over the course of a couple of outings. Fixed without replacing any packing.

If you wish to stay with that type of shaft seal then I would respectfully suggest you use Teflon impregnated steam packing from any industrial plumbing supplies as its way cheaper then 'Marine' shaft seal packing which is of course exactly the same stuff.
I found that the PO on our boat had overtightened the seal and it had worn the shaft so we had to turn the shaft end over end. I binned the old seal and fitted a PSS seal and simply do not have any leaks now, I've used them for 15 years and swear by them. I have absolutely no ties with them except as a satisfied customer.

Just a few photo's by way of explanation.
1, Enthusiastic tightening the packing and lack of grease leads to overheating.

2, While its all stripped down its time to replace the cutlass bearing, drifting out the old. New shiny one standing up behind.

3,Shaft out for cleaning and checking for being 'true' (no bending).

4,If you look just by the drill handle you will see the 2 wear marks on the shaft caused by overtightening. Fortunately the shaft could be turned end over end so the worn portion was in a different non critical position.

These are my reasons for fitting the PSS seal.