Shaft Tube Discussion

El Mar

Admiral
Lite User
Joined
Sep 1, 2011
Posts
7,105
Likes
2,837
Location
Westbrook, CT (The Asshole State)
First Name
Bryan
Boat Make
43 Tiara Open DDEC, GradyWhite 268 Islander, 18 Donzi Classic, 15 Boston Whaler Sport ETec 60

jerseysportfisher

Rear Admiral
Joined
Feb 13, 2012
Posts
1,181
Likes
149
Location
Communist part of NJ
Boat Make
Bertram 33SF
Here is a topic that I have seen thrown around many different boards, but never really discussed in detatil. I know Capt. Larry has some good info and pics about the retrofit on his 31 JC and have seen Ken Flowers artfully install them on his builds here, and I'm sure First Team as well as others know plenty about them.

With all the info here, fill a novice like me in about the finer points of shaft tubes, pros and cons, installs, etc.

according to conventional wisdom, and i would presum experimentation. The rotation of a shaft creates more frictional drag, it has been said that adding a shaft tube even though its larger in diameter, helps alleviate the extra drag caused by the shaft rotation. Thus picking up speed
 

tunaorlater

Admiral
Joined
Sep 9, 2011
Posts
4,385
Likes
2,460
Boat Make
40' Northern bay
In a downeast no part of the tube is in the water it's all in the keel so I don't understand how it would reduce drag?

No need for a keel full of water and a big chunk of brass inside and out of hull. Thus reducing weight by a lot. Also you can taper the keel back for better water flow to prop.
 

Helen L

Commander
Joined
Jan 12, 2012
Posts
481
Likes
58
All I know is mine has a pin hole leak. It's exposed and easy to get to. I was planning on sealing it by glassing over the tube using epoxy when I haul out in a few months. Previous owner tried 5200 before I picked it up but it was in the water and didn't seal it up.

Anyone that's attempted something along these lines before please chime in.
 

petrel

Rear Admiral
Joined
Dec 17, 2011
Posts
1,583
Likes
378
Location
NC
Boat Make
56' DMR, 31' BHM
Since you brought that up, my 31 BHM, interestingly enough documented as an Otis boat from 1980, has a wet keel. I'm curious to know how many other models of downeasters have wet keels by design.
 

Blitzen

Admiral
Joined
Sep 1, 2011
Posts
4,456
Likes
3,236
Location
Sumday Isle, RI
Boat Make
Flowers Boat Works 46, 1991 Boston Whaler Outrage 19
I wonder more about cost and speed of building a downeast boat that influenced whether or not the boat got a shaft tube. Let’s face it, it requires a lot less work and money to go without. I am sure boat design and purpose of use may benefit from having all that water in the keel in some cases.
My Repco had a wet keel and I can't imagine all the old marine life that ended up inside over the years and it was a bit too snappy for me on the drift.
 

BillD

Admiral
Joined
Sep 1, 2011
Posts
6,643
Likes
2,162
Location
Portsmouth NH, boating out of the mighty Merrimack
Boat Make
25 Terry Jason with Cummins 370 power
I wonder more about cost and speed of building a downeast boat that influenced whether or not the boat got a shaft tube. Let’s face it, it requires a lot less work and money to go without. I am sure boat design and purpose of use may benefit from having all that water in the keel in some cases.
My Repco had a wet keel and I can't imagine all the old marine life that ended up inside over the years and it was a bit too snappy for me on the drift.
Help me out here.

Does a shaft tube require a separate cooling water source (engine) same as a dripless shaft seal?

Or does the shaft tube "fill with water" through the cutless bearing?

Curious?
 

Helen L

Commander
Joined
Jan 12, 2012
Posts
481
Likes
58
Mines just filled with seawater through the cutlass. I think that's how they all are.

Maybe First Team can help me out. Small pinhole leak in the tube. Easy enough to get to, it's above the normal water level in the keel. Fiberglass over the tube out of the water with epoxy? Maybe 5200 smeared all over?
 

Blitzen

Admiral
Joined
Sep 1, 2011
Posts
4,456
Likes
3,236
Location
Sumday Isle, RI
Boat Make
Flowers Boat Works 46, 1991 Boston Whaler Outrage 19
Help me out here.

Does a shaft tube require a separate cooling water source (engine) same as a dripless shaft seal?

Or does the shaft tube "fill with water" through the cutless bearing?

Curious?
Bill,

If there is a bearing on the engine side of the shaft tube it will require a water feed to make sure it is kept cool and wet. There are some installs where the tranny is too close to the stuffing box and will prevent the use of a bearing at the upper end of the tube, in this case no water feed is necessary.
 

BillD

Admiral
Joined
Sep 1, 2011
Posts
6,643
Likes
2,162
Location
Portsmouth NH, boating out of the mighty Merrimack
Boat Make
25 Terry Jason with Cummins 370 power
Bill,

If there is a bearing on the engine side of the shaft tube it will require a water feed to make sure it is kept cool and wet. There are some installs where the tranny is too close to the stuffing box and will prevent the use of a bearing at the upper end of the tube, in this case no water feed is necessary.
John,

If I understand your 36's shaft install correctly it has a "traditional" flax pack bearing/tube/cutless. Correct?

The bearing aft of the tranny??? Is it water fed from the engine??

Thanks,

Bill
 

Blitzen

Admiral
Joined
Sep 1, 2011
Posts
4,456
Likes
3,236
Location
Sumday Isle, RI
Boat Make
Flowers Boat Works 46, 1991 Boston Whaler Outrage 19
John,

If I understand your 36's shaft install correctly it has a "traditional" flax pack bearing/tube/cutless. Correct?

The bearing aft of the tranny??? Is it water fed from the engine??

Thanks,

Bill
Correct with water feed from the engine and I took out the traditional flax and changed it out with DuraMax.

There is a cutless bearing inside the upper end of the tube before the stuffing box.
 

petrel

Rear Admiral
Joined
Dec 17, 2011
Posts
1,583
Likes
378
Location
NC
Boat Make
56' DMR, 31' BHM
Was called Shadow for many years, I don't know if that was the first name. Official number is 630047. I think at least four other people have owned her previously down here in NC.
 

petrel

Rear Admiral
Joined
Dec 17, 2011
Posts
1,583
Likes
378
Location
NC
Boat Make
56' DMR, 31' BHM
My first post here had a photo:

Lets see em - Page 8 - Downeast Boat Forum

The previous owners didn't give her much love, so we took out all the old wet balsa core (cabin top and washboards) replaced it w/ Nidacore and in the process, we extended the cabin.

Still got the wet keel- no tube.
 

petrel

Rear Admiral
Joined
Dec 17, 2011
Posts
1,583
Likes
378
Location
NC
Boat Make
56' DMR, 31' BHM
She hasn't been gray for a long time. And she's had a major facelift after many years of neglect to the topsides.
 

captainlarry84

Rear Admiral
Joined
Sep 13, 2011
Posts
1,295
Likes
233
Location
Freeport NY
Boat Make
KristenFormer Charter Captain
Wet Tubes

In a downeast no part of the tube is in the water it's all in the keel so I don't understand how it would reduce drag?

No need for a keel full of water and a big chunk of brass inside and out of hull. Thus reducing weight by a lot. Also you can taper the keel back for better water flow to prop.


Tunalater is correct on his assessment I agree on all he states. The shaft tube should be fed by water off the engine. In doing so it not only lubes the cutlass bearing but is also feeds the stuffing box. On my install I also added two feed hole in the keel just in front of the cutlass bear. This way should the feed clog at least the cutlass bearing is getting some water fromn the additional feed holes. You can see the feed holes in the photo attached.
In a wet keeled boat in addition to carrying a keel full of water the shaft is always spinning with full water contact. Unlike the wet tube which is just forcing water down the shaft to feed the cutlass bearing.
It is true that wet tubes are only used on keeled New England boats, However I did see a beautiful custom twin screw Carolina boat at Cape May sporting wet tubes all the way back and into the struts. The boat had a cruise speed of 28 knots and the owner swears by them, which agrees with the theory stated by Jersysportfisher. I would image that the custom struts to hold the wet tubes must be very expensive.
As far as the pin hole does I would just chanter the hole and fill it with Hull & Deck Puddy or Marine Tex. Both are like iron.

March photo 06 038cl.jpg

CCI12182009_00001.jpg

kristen 009.jpg
 
Top Bottom