Prop Shaft Seal question

[doug_c]

Hi everyone, a while back I posted about my 92 supra comp taking in more water than it should. I got some great advice and a lot of people said I should probably start with the propeller shaft. I've got my boat back from storage and this weekend I opened everything up to get a closer look (see attachment). Before I go too much further now, what is the proper way to pull this all apart? Looks like the first step will probably be to back off the smaller nut to loosen the housing. I'm thinking I'll have to cut that hose off and get a new piece when i put it back together. Then does the shaft just slide right out? I'm assuming there is some sort of packing material or seal on the water facing side. Sorry for all the questions, I just don't want to mess it up. Thanks in advance!

Doug

prop.jpg

[docdrs]

There is packing cord inside the big brass nut. You just have to repack it. You don't have to remove the entire assembly. You may just need to tighten the packing nut to reduce the water dripping.

Here is a instruction link http://www.moomba.com/msgboard/showt...-Brian-Raymond
Here is a great link with pics http://www.pbase.com/mainecruising/stuffing_box

[michael hunter]

Water is required to lubricate conventional packing, so a properly adjusted stuffing box can be watertight when the shaft is stopped, but it must drip when the shaft is turning. Two or three drops per minute are adequate. It is not uncommon to see stuffing boxes leak at a much higher rate. This doesn't harm the shaft or the stuffing box, but the spinning shaft will sling this excess flow all over the engine compartment, leading to rampant corrosion of the shaft coupling, the transmission housing, and everything else getting sprayed. Even more disastrous, it puts an unattended boat at risk of sinking. If your stuffing box leaks more than 8 or 10 drops a minute, it needs servicing. Tightening the stuffing box nut a half turn is all that is required to reduce the leak, but the location of the stuffing box can render this job far more difficult than it should be. Access can be especially challenging in boats with V-drives and in sailboats.

The first step in stuffing box adjustment, then, is to figure out how to get two wrenches on the box--one for the lock nut and one for the adjusting nut--and how to position yourself so that you can pull on one while pushing on the other, and vice versa. You can use pipe wrenches to turn the nuts, but adjustable packing nut wrenches tend to be easier to handle in confined spaces. If the stuffing box is above a deep bilge, tie a retaining line to the wrenches before you start. With your wrenches on both nuts, hold the adjusting nut and turn the locknut clockwise to release it. Back this nut off a couple of turns. Now turn the adjusting nut clockwise until the dripping just stops.

CAUTION: Some stuffing boxes are rigidly attached to the hull, but most are connected to the shaft tube with a length of flexible hose. You do not want to twist this hose or twist the stuffing box inside the hose. If the adjusting nut does not turn easily, use a pipe wrench on the stuffing box flange--located just forward of the hose--to keep the box from turning with the nut. If the box is corroded, back off the adjusting nut several turns and wire brush the box threads bright before making the adjustment. Give threads and nuts a heavy coat of Boeshield T-9 (or some other corrosion blocker) to avoid this problem in the future.


After you make this initial adjustment, you are going to need to check the drip rate with the shaft turning. You can do this either with the boat underway or with the transmission engaged in forward and the boat securely tied in the slip. With the help of a flashlight--and a mirror if you need one--count the drops per minute. If it is more than two, tighten the adjusting nut slightly. If you cannot make this adjustment without putting body parts or clothing in dangerous proximity to the spinning shaft, stop the engine, make the adjustment, then restart it to check the drips. When the drip rate is one or two drops per minute, stop the engine. Hold the adjusting nut securely so that you do not alter the setting, then tighten the locknut against it. Before you extract yourself from your access position, carefully check the strap clamps that attach the hose to the stuffing box and to the stern tube. These inevitably corrode at the bottom, so you may need a mirror to check them. Better yet, release each one and rotate it to view all sides before retightening. Do this one clamp at a time.

[doug_c]

That's great info, thanks a lot Michael and docdrs. I'll have to do some more adjusting once I'm in the water by the sounds of it. Once more question, where the shaft actually leaves the hull (brass fitting) is there anyway water can leak there with old sealant or a loose fitting? Thx.

[michael hunter]

You should have the drops of water coming out of the large brass nut at the far end closest to the trans.

[docdrs]

You should have the drops of water coming out of the large brass nut at the far end closest to the trans.

You do not have to have water dripping into your boat. That is more of a max thing 1 drop per 30 seconds. There is water up to the point of the stuffing and if you can get it so it does not drip you are fine. There will be no over heating of the shaft. This is a old wives tale. But as Michael says this is the place where you will see water drip and he gave you the max amounts you want to see. Personally I don't like water in the boat and the less drips the better.

[doug_c]

Good stuff, thanks guys. While the boat is out of the water I'm going to repack the cords with some GFO just for peace of mind. Great info as always. Cheers.