Hunter 37C Stern Tube/Shaft Log Replacement Question

[Rumbero]

After dropping the rudder I went after another key thing to check before I go back in the water. I wanted to know the condition of the stern tube, prop shaft, and also to replace the coupler with a split version. After separating the coupler from the transmission, and then the prop shaft from the coupler, I pulled out the prop shaft (bronze) and disconnected the PSS shaft seal. I have to say, without having first removed the disintegrating water heater and fuel fill hose this would have been a lot more difficult.

Once the PSS was removed I saw the “bronze” stern tube was compromised. New replacements can be sourced from Southeastern Foundries Corp. (SFC) as part no. HM-312930 for $100 + shipping. I found them to be very responsive and helpful.

I learned that the replacement stern tube isn’t bronze, but Brass 836 alloy. I’ve always understood use bronze, not brass, below the waterline in a salt water environment. SFC assured me that they have always produced the stern tubes from Brass 836–which is about 5% zinc—and that it was suitable for salt water. Because the original is 40+ years old and mostly intact, I purchased it.

My questions are for anyone who has done this before:

Any specific tips on removing the original stern tube and bolts?

Did you find that the stern tube was bedded with 5200 (Satan’s glue) or similar?

Did you find the need to build up the mating surface on the hull in order to assure a perfectly centered prop shaft in the stern tube? If so, what did you use or recommend for that purpose?

The SFC stern tube comes without bolts. Beyond length and size, what material for the bolts and nuts are recommended for attachment?

As always, thanks in advance for your responses.

 

[Rumbero]

Quick follow up. The original H37C stern tube is 1 5/8” and the replacement from SFC is actually 1 3/4”. So I will be enlarging the hole with a hole saw. There is not a lot of room under the current hole to enlarge it. By going to a 1 3/4” hole (an extra 1/16” all the way around) I should just clear the part of the hull on the inside and bottom of the stern tube where the new PSS bellows will mount.

The old stern tube came out after I used a heat gun to soften up the sealant/adhesive. Upon removal, it looks like the last person who put in this stern tube—either the Hunter factory or some prior owner—used stainless carriage bolts into the brass stern tube. Little wonder it was corroding the way it did. The price for 2 bronze 3/8 x 1.5” carriage bolts, 2 fender washers, 2 lock washers, and 2 nuts: $16. Ouch.

 

[Rumbero]

Update and heads up:

If you’re replacing your 37C stern tube like I just did with the one from SFC, you’ll need a 1 7/8” hole saw to enlarge the hole for the new 1 3/4” stern tube. This is not a commonly stocked size in hardware stores. Home Depot, Harbor Frieght, and Ace Hardware did not have this size in stock. Luckily, a guy at the yard had one I was able to borrow.

 

[DianaOfBurlington]

I would use a tube of G10. I would not even consider anything metal for this. This is not 1935. This is a new world.

I would (will; as I’m doing this for my own boat) cut a big-enough hole in the hull . Locate the G10 tube with the shaft and all else in place. Make sure the tube is too long so you can fit the PSS on the front and have tube sticking out. Align everyone to be happy, strut, prop, coupling, engine mounts, PSS thing and tube with enough room to flop around if your hole is too big. Then spin the engine - even start it up - to check alignment (the tube will just spin on the shaft). When it’s all cool, ‘glass it where it lies, support the front end, cut off the back end , and when the ‘glass cures just trim off the outside, fair with structural material (‘glass) and done.

I’m sorry but I see absolutely NO reason to install a bronze shaft log on a fiberglass boat (really any boat). With all I know about this very job and many others, the installation is easier, the maintenence is nearly nil and the longevity makes it a no-brainer.

 

[DianaOfBurlington]

BTW - 5200 is not ‘the devil’s glue’. Sheesh. It’s an extremely strong, extremely versatile polyurethane adhesive compound whose legitimate uses in boatbuilding or repair outnumber anything you and I can name in the next ten minutes. The problem is that many people do not understand its properties and misuse it, often getting caught up in the ‘I understand this, therefore it’s my answer for everything’ syndrome. (vis.: butyl, silicone, etc. - all far more limited applications). That said, we were installing decks on hulls in 1973 that are still holding those boats together today. There’s no point in heeding fads or misinformed advice in this. If it works, learn why and then choose the best.