Why does water come through the shaft seal?

J

jim1744

New Member
Jul 12, 2009
4
Long island NY
Boat Info
2005 Sundancer
Engines
(2) 8.1 Merc Gas 496 ci.
360HP
When I was winterizing my 360 Sundancer (on dry dock) I noticed that when pulling water into the strainer to run up the operating temperature that the cooling water was discharging from three places. 1) Side exhaust above the water line 2) Under the boat and under the water line exhaust 3) The shaft seals.

Why would it come from both shaft seals when I am only running one engine at a time? Why even one shaft seal? Is this normal? Is there a positive water pressure on the seals when the water pump is operational?
Any ideas?
Jim

2005 Searay Sundancer Twin 8.1 360HP 496 cu inch gas engines
 
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I think it is to lubricate the shaft/seals and keep them cool. While running one engine in gear while in the water the other shaft will spin while in neutral so this might be a safety feature. I am sure that someone will correct me if I am wrong. But I know its important to be certain you get anti-freeze out those shafts when you winterize!!
 
Dripless shaft seals must be lubricated with pressurized water while turning or they can overheat from friction and melt. Don't ask exactly how I know this... Let's just say it's expensive NOT to ensure that you have good water flow going to them each season. :smt013

The water in my case comes off one exhaust manifold off each engine via a small hose which supplies pressurized lake water directly to the shaft seals. The other end of the hose is attached to a fitting on each respective shaft seal.

In my case, I did not have a "crossover" line that would ensure a redundant water supply just in case one engine wasn't running or (in my case) the hose became plugged. If you have a crossover hose, it doesn't matter if only one engine is running, water is sent to both shaft seals.

Regarding your question of water leaking out of the shaft into your bilge... I don't think that should happen. It doesn't happen when in the water. The water normally flows into the seal's housing, the back chamber of the seal, and then out the shaft tube to the great blue sea - not between the seal and prop shaft, and subsequently into the bilge! That wouldn't be a very good "seal" now would it? :huh:

It may be possible that the shafts are out of alignment enough just by being on the hard to cause a gap on one part of the lip seal. That's why you don't check alignment until the hull settles in the water for a few days.
 
Thank you for the responses, It was a good amount of water coming out the shaft seal to the underneath of the boat. Like you said, water is not a very good seal. When the engines are off, will water go the opposite direction and come in to the bilge? I guess I have more investigation before I splash in the spring.
 
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I just experienced the same issue. This is the first time I was winterized on land. I noticed today that liquid was draining out from the shaft exit area/hole under the boat. After further inspection it appears to be antifreeze - which was just pumped through the raw water cooling side of each engine 3 days ago. It was a not a large volume just drops, a little more from one side than the other. I wil be interested to see wha you find out and what anyone thinks.
 
Like they said - water is pumped through seals when engines are running. It drains overboard. With engines off, it should quit after the lines syphon out.
 
I've been interested in this issue from the perspective of whether to drain and fill my engines (as recommended by Cummins) or to continue my normal method of pumping antifreeze out of a bucket through the system. Looks like concern for the shaft seal needs to trump on this. Here's some info from the manufacturer (www.tidesmarine.com):

1. Check the water injection system on each engine at the start of the season and every six months.
  • Before starting the engines, loosen the 2 hose clamps on the water injection fitting hose connected to the shaft seal water injection fittings and "snap" the black plastic cap (attached to the base of the injection fitting) over the top of the injection fitting.
  • Hold the water injection hose in a bucket and have a mate start the engine. Water should begin flowing through the hose and into the bucket. Have the mate run the engine up through the RPM range to make sure a steady flow of water moves through the hose at all times. You should be getting a minimum of 1 gallon (4 litres) per minute at idle.
  • If the flow of water appears restricted or slows at any point in the power range, shut off the engine. Then, locate the source of the water in the engines raw water cooling system and remove the water injection hose. Water should flow freely. If not, inspect the pickup point for debris and check the hose for a blockage. Once water flow is appropriate, re-attach the hose and clamps atthe water pcikup point. Tighten the clamps.
  • Check the hose route to make certain it is free from any sharp bends or kinks.
  • Shut down the engine if it is running. Remove the black plastic cap from the shaft seal injection fitting and re-install the hose and clamps. Tighten the clamps.
  • Repeat the above steps for the second engine if applicable.
2. Periodically inspect the shaft seal for signs of water drips.
  • Wipe the underside of the shaft seal with your hand. Look for signs of salt residue or moisture. Remove deposits with a dry cloth and check the unit again after the next use. If deposits return have the mate inspect the unit when the vessel is underway.
3. I winterize my boat every fall. What special steps do I have to take to winterize my shaft seals?
  • Tides shaft seals require NO raw water to be left in the seal. The raw water system needs to be flushed with a 50% antifreeze mixture until you see antifreeze running out of the stern tubes.
 
Ok, any idea on this?

My Buddy's 2000 380 is leaking water from what appears to be the back section of the Blue boot that covers the actual shaft coming in the boat (starboard side). I tightened the 4 hose clamps a little and I still had room to tighten a little more but i didn't want to over tighten it for fear of crushing the blue hose or the actual mold that the shaft slides inside of.

The leak slowed just a hair, but we discovered that when we closed the seacock to the engine, the leak stopped. Opened it back up, and the leak appeared again.

What gives:huh: Any thoughts:smt100
 
Kid, here's some info from a seal maintenance document I had stored on my hard drive, I believe it came from the Tides Marine web site:

(Troubleshooting)
1) Determine exactly where the leak is. Is it between the seal and the shaft or is it
between the hose and seal body? Are there rust stains or water stains in the bilge
under the seal and or hose? If not, it may not be the seal causing the water in the
bilge. Is there rust on the stainless steel band below the seal?
2) If it is the seal:
a) Does it leak at rest? Could be a bad spot on the shaft or a damaged seal. Move
seal forward to a different place on shaft to try to get it to stop leaking. You may
have to polish the shaft before moving the seal forward. If this does not work,
install spare seal from carrier kit if equipped.
b) Does it leak underway? Could be seal or bearing. Polish spot on shaft and move
seal forward to a different place on shaft.
c) Grab an injection fitting and pull the part sideways. Does it leak more when side
loaded? A lot more? If not, probably just the seal. If yes, probably the bearing.
Replace unit. Some leaking when side loaded is normal for Sure Seals. This is
due to the larger tolerances used in the new parts.
d) How many hours are on the seal? How old is the boat? Less than two years old
or 2500 engine hours? Is it a warranty? If so, collect information and begin
warranty form.
3) If it is between hose and body:
a) Loosen clamps and make sure that the split bands are positioned 180 degrees from
each other. (Strong Seals only).
b) Reposition clamps so that they are about half on half off the stainless bands and
retighten. Be sure not to over tighten. (Strong Seal only)
c) If this does not work, loosen the clamps and slide the bearing out of the hose far
enough to put a bead of silicone around the forward edge of the forward split
band. Reinstall with the forward clamp half on half off the split band. DO NOT
OVER TIGHTEN THE CLAMPS! (Strong Seals only)
If you can not determine exactly what the problem is or the problem persists after trying​
the above, turn the call over to a technician at Tides Marine. (800)-420-0949
 
I had a similar issue this year, although the cause what nothing near what i thought it was.

I was getting a slow, steady drip from underneath both shaft seals. I was pissed off, since they had been replaced in 2008. The leak(s) were happening at the same rate (about 4-5 gallons a day) whether the boat was running or not.

I had a buddy come and check it out (very mechnaically inclined) and showed me it was not my seals at all....it was my rudder packings. The leak was very slight, very steady....and the very thin trail of water came right down into the engine bays and dripped right past/under the shaft seals, making it look like my shaft seals were leaking.

Three turns on the rudder nuts with a packing wrench and they stopped.

I went from being pissed to being ecstatic. It was a no-cost solution and I had been emotionally preparing myself for a major, season-ending repair.

So, make sure you are 100% certain it is the shaft seals.
 
I have a cross over water line that adds a second water line to each dripless seal... This is for whe you run on one engine the seal on the oposite engine remains under pressure... So when you winterize you should see water coming out of both shafts...
 
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