Sealing Struts with Lip Seals

[CraigP]

This thread goes hand in hand with the Dual Vortex Hydro build. There is a bit of info for this particular procedure, so I created a new thread. The purpose of this work is to provide a definitive seal at the end of the strut that accomplished the following:

1) Doesn't let water into the Stuffing Tube/Strut Assembly
2) Doesn't let grease and lubricants out
3) Keeps drag of the seal assembly to a minimum

You will need a good drill press or mill. I have a drill press. You also need a Machinist's Vice, as pictured. You will be machining into the back of the strut a 5/16" counter bore, to a depth of 0.150". I have had very good success using the Speed Master Struts, but I've also been able to do this mod on a stock UL-1 strut. You need at least an outside diameter of 0.350" to leave enough meat to make it reliable. I also install a graphite thrust washer, available from OSE. Finally, there is a retainer clip that is pressed into the back of the strut to keep it all together. This is a modified #10 split, helical lock washer, Medium thickness. I have this broken down in its steps, in order.. Note that the C-Bore tool needs a Pilot Tool inserted in the center hole of the C-Bore tool. The part number is P1873. The pilot should be set so that the face of the pilot stands 0.25" from the face of the C-Bore tool, using the set screw provided. Here are pics of the parts needed:

[CraigP]

Setting Up the Vice

The Vice needs to be rigidly set to the table of the drill press or mill. You cannot do this free hand! Don't even try!! I use a 1/2" bolt to do this. I keep everything lose until I get things lined up. I use a piece of 3/16" SS rod, I've had since my nitro days, 30 years back. I put this in the drill press chuck and use it to get a good alignment. I'm sorry, but I don't have to patience or words to exactly describe this. I'm good in a machine shop, so it's just instinct. Hopefully the pictures will get you going in the right direction.

[CraigP]

The Setup is the hardest part. Once that is accomplished, this C-Bore Cutter makes short work out of this! The first one is the hardest, and you may want to get your feet wet with an old strut you have laying around. I any regard, once everything is tightened down, put plenty of oil on the strut and cutter. You want to use a moderate tool pressure with this cutter. Keep cutting until the cutter as reached to top of the Lead/Teflon Bushing. This should be set 0.150" from the back of the strut. On short prop shafts, I use 2 bushings, spaced out as far as I can get them and still fully supporting the prop shaft. On the longer shafts, I've used 3 bushings. I Lock-Tite in the bushings so they don't slip. These bushings will last a very long time, as long as they are not subjected to water. As long as the grease is on them, they will hold their ID very well. The floating bushing isn't well suited for this application, because you don't want it bumping on the lip seal while it's running. You need the bearing to stay in position. A roller bearing will work too, but they should be unsealed bearings so the grease can come thru and lubricate the lip seal. I've had a hard time finding those. Travis (kfxguy) is very good with the roller bearing solution. But I find the bushing adequate and simple to install.

[CraigP]

Once the C-Bore is machined, make sure to blow out and clean all chips from the strut. The Teflon is delicate. You first install the graphite washer into the C Bore. This is used to protect the face of the lip seal from the rough finish on the bottom of the C Bore. It is not necessary to have a mirror finish there. You do need a very good finish on the walls, which is what the outer lip seals against. If you do this on a mill, this cutter will produce a very good machine finish on all surfaces, my drill press has some play in it, but it still works, so don't be discouraged! After the graphite washer, install the lip seal with the lips facing the washer. See pics for reference:

[CraigP]

Next comes the process of modifying a Medium #10 helical spring split lock washer to make a retaining clip. You first put it in the vice so the splits are facing up. I use pliers to bend the washer to take the helical out of it. When finished, it should look like a flat washer with a split in it. This washer should be smaller than 5/16", which is 0.312" in diameter. I then spread the spilt outward, as pictured, to get the OD to 0.325". This makes a perfect retaining clip! I've never had one back out while running. If you need to remove it as some point, just use a small flathead screwdriver and gently pry it out. The retainer clip is set by putting it on top of the C-Bore, is should be too big. Then, I put it in the vise and squeeze them together, to make a finished assembly. And you're done!

[CraigP]

Here's the finished product back on the boat!!

[vinnyp]

Real nice job Craig. I like it a lot.

[Bp9145]

Man, I wish I had the tools/machine. that's awesome. But, I could just send my struts to you Craig, for a fee of course. . . .great stuff.

[CraigP]

What kind of struts do you have, and how many? Doing multiple struts makes the most sense because shipping is such a rip off these days! Speed master is a slam dunk. Other struts need some measuring...

[Beaux]

Nice job, gets me thinking.

[Old School]

Makes you wonder why a manufacturer does not offer a sealed strut.

[CraigP]

Ive asked myself that question for a long time. One of the things I really didn’t like with my old nitro boat back in the day is how it left an oil slick behind it. I actually got thrown off of several ponds in California because of the oil contamination. With all my boats being FE and this sealed Strut, I have no contamination issues any more! And I really don’t like having to redress the grease every 3-4 runs. You have to loosen everything up. I like to tighten the motor collet and leave it. It can give you a reason to ponder your grease choice. Most want a heavy, sticky grease so it stays longer and at least leaves a residue. Now I’m able to use a much lighter grease, saving on frictional loses. I’m using Proboat Marine Blue (which is heavy) and add 3 in 1 oil to that, to bring the viscosity down. I’ve tested the seal to 50psi, it’s a stout little bugger...

[srislash]

Well I woke up thinking, ‘ damn, I need to do this on BlownAway ‘!! So parts collecting I shall go.
Thanks Craig.

[CraigP]

I just got a Speedmaster skeg Strut for the Skater32 and I’m going to seal it today! You know, I tried putting a skeg fin on the inboard right sponson, just past half the hull length. It made the tripping problem in the corner worse. Some corners were great, but if it hops up alittle, the re-engages, it trips and spins. So I took it off and going with the skeg strut, because it was showing signs of turning much better with dropping the strut position. That cat is my little problem child... Perhaps my expectations are too high, I just want him to grow up and be a doctor, lol!!

Blown Away needs that detail! Now you can join the zero pollution crowd AND only grease those struts once a season... And on a dual, that’s saving some time, time that can be spent running it!

[golfito]

Excellent Craig!
You must patent it!

[CraigP]

Thanks, but nothing to patent... It’s just a lip seal...

[Shooter]

Nice job!