Discount Inboard Marine (DIM) Featured Product(s)

PSS Packless Shaft Seal

No More Water in the Bilge!
By Keith Bagley, CorrectCraftFan.com
July 2005

Previous DIM Featured Products: Humminbird Depth Sounder Sherwood Water Strainer with Engine Alarm ACME #540 13" x 12 pitch 3-blade NiBrAl

I just purchased an '86 Sliver Nautique at the beginning of the summer. Beyond my excitement of owning this rare special edition Ski Nautique, I was delighted that it came with lots of upgrades and extras. Of the many improvements, I was most delighted about the PSS Packless (and dripless) Shaft Seal that had been installed.

Where the shaft passes through the hull is a very vulnerable part of any inboard driven boat. For starters, there is a 1" (or 1 1/8") hole straight through the hull. Second, through this hole passes your boats drive shaft that spins in excess of 4,000 rpms. The demands on the shaft seal are immense – keep water out while allowing friction-free, high speed rotation of your drive shaft. It fact, the shaft seal is so important that Correct Craft built into the floor of its boats the removable round plate that allows for regular, daily inspection.

The traditional shaft seal (a.k.a. 'stuffing box' or 'packing gland') is a wax impregnated rope, wrapped around the shaft. For proper lubrication, it is designed to drip water during operation at a rate of several drops per minute. According to the Correct Craft manual, "it's recommended that the seal be checked frequently for the presence of any water leakage other than a few drops per minute". If excess leaking is found, you are required to tighten the gland nut down on to the packing, through a series of steps.

The PSS Shaft Seal, on the other hand, uses a high density carbon graphite flange and tension seal that works great for fresh water use and is critical for brackish or salt water use. According to the company, "the carbon flange [is] held in contact against a stainless steel rotor which turns with the shaft. The carbon flange is attached to the boat by a nitrile bellow which, with the help of water pressure, produces a constant contact between the carbon and the stainless steel ring." The result is a 100% watertight and totally maintenance-free seal.

The PSS Shaft Seal comes in two versions, one for inboards operating under 12 knots (about 14 mph) and another for inboards operating above 12 knots. The higher speed version uses additional water from the intake to provide lubrication. The kit comes with a T-adapter that mounts inline with one of the exhaust cooling intakes. A supplied hose is attached to the 3/8" barb and then attaches to a matching 3/8" barb on the PSS Shaft Seal.

'T' in intake and PSS Shaft Seal installed

Installation of the PSS Packless Shaft Seal requires removal of the shaft coupling which then allows for removal of the old stuffing box. Removal of the shaft coupling requires clever use of a spacer to push out the shaft from the shaft coupling. Because my boat already had the PSS Packless Shaft Seal, I didn't have to install it. However, you can find detailed installation directions, with diagrams, on the PSS Shaft Seal site or you can always contact Discount Inboard Marine for their excellent technical support.

Before I saw the PSS Packless Shaft Seal in operation, I didn't realize how great it was. I have to tell you, this completely water tight, maintenance-free shaft seal might be one of the greatest inventions for the inboard boat owner. Not only can you take comfort in the fact that such a critical part of you inboard will function properly it's also such a relief to lift the engine cover after a full day of use on the lake and find absolutely no water in the bilge. And the best part about the PSS Shaft Seal is you can install it now and never worry about it again.

Views expressed in this analysis are solely those of CorrectCraftFan.com and not those of Correct Craft, Inc.