Tahoe 23 Prop Shaft Diameter?

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TomB
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Tahoe 23 Prop Shaft Diameter?

Post by TomB » Mon Aug 13, 2018 8:28 am

I sat down this weekend to order a Prop Strut. The Instructions include a hardware list calling out a 14* strut for a 1" shaft diameter, a 12* shaft log for 1" shaft diameter, and a 1 1/8" stuffing box. Does a 1 1/8" stuffing box work on a 1" shaft? 14* strut and a 12* shaft log, how does that work?

I also see that ski boats seem to be equipped with 1 1/8" shafts, which would be significantly stronger.

I am planning to use a basic 300 HP motor (whatever that is), a basic transmission (whatever that is), and a 13x13 prop (whatever that is). I've looked at that stuff, but I'm more a wood guy than a gear guy, so it will be solved later, much later.

For now I'm trying to prep for a prop shaft hole and a rudder hole. So what shaft diameter will I end up with?

Once I know the shaft diameter, figuring out/confirming the strut geometry and get to the right strut and strut bearing should be easy.

Any comments on my planning would be most welcome.

Thanks,

Tom

Brad Tucker
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Re: Tahoe 23 Prop Shaft Diameter?

Post by Brad Tucker » Mon Aug 13, 2018 10:10 am

I'm running a 1" shaft behind a 240hp 351, slinging an Acme 13x13 3 blade prop via 1:1 transmission. With 300hp you may end up with a different pitched prop.

Are you sure the stuffing box isn't the one for the rudder shaft? I can't recall 100% but I think it is a 1 1/8" rudder shaft.

As far as the difference in degrees, you've got me on that one. I ordered the strut, rudder and shaft log as listed in the plans. In saying that, I had to shim the stuffing box with a wedge who's highest point was the forward edge, by, yep, a degree or two. I seem to recall that it was the closest log angle you could get to the needed angle, but I'm not sure. I think it would have worked, but I wasn't comfortable with it being off. If you go with a traditional packing seal, the rubber hose will have some play in it, so it doesn't have to be dead on correct. You just don't want the prop shaft rubbing it. I put a dripless seal in mine, because I saw a shaft that had a groove worn in it from a packing type seal. That was another reason I wedged the log. I wanted the seal to have even pressure placed on it.

TomB
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Re: Tahoe 23 Prop Shaft Diameter?

Post by TomB » Mon Aug 13, 2018 4:49 pm

Thanks for the feedback Brad. 300 HP is just a guess, shouldn't be more than that, probably a GM 350.

The stuffing box is called out as 1 1/8" for both the prop shaft and the rudder.

Tom

DaveM
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Re: Tahoe 23 Prop Shaft Diameter?

Post by DaveM » Mon Aug 13, 2018 5:04 pm

Your question regarding shaft log requirement. My plans call for a 13.75 (say 14) degree strut with the propshaft and motor at 12 deg.. My thinking was the strut is a 14 deg. from keel, the 12 deg. reference is motor and prop shaft from motor stringers.

TomB
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Re: Tahoe 23 Prop Shaft Diameter?

Post by TomB » Mon Aug 13, 2018 6:27 pm

Dave, I'm no expert but I see the geometry like this. The prop strut angle is the angle between keel and shaft, per instructions, 14*. The shaft log is the angle between keel and shaft, per instructions 12*. Since the keel is straight in the area of the prop shaft I would have to warp the hose between log and stuffing box 2*. I can use a down angle tranny and tip the engine a little so the slope of the keel should not be an issue.

Tom

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kens
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Re: Tahoe 23 Prop Shaft Diameter?

Post by kens » Tue Aug 14, 2018 3:05 am

DaveM wrote:Your question regarding shaft log requirement. My plans call for a 13.75 (say 14) degree strut with the propshaft and motor at 12 deg.. My thinking was the strut is a 14 deg. from keel, the 12 deg. reference is motor and prop shaft from motor stringers.
Measuring the shaft, it is a fixed angle to the keel; engine angle to stringers doesnt matter
If you got a small block V8 (any make, any HP) and a 1:1 tranny, then a 1" shaft is correct.
you will end up with something like a 13x13 or similar prop (give or take a bit)
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

DonnD
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Re: Tahoe 23 Prop Shaft Diameter?

Post by DonnD » Tue Aug 14, 2018 8:27 pm

Hi Tom. Great progress on your build. Very impressed with how you laid out the final mahogany layer on the sides.

The strut I ended up with is a 14* - item number 90-116 on Glen-L's online store, with the corresponding Blackfish bearing (item # 90-352) suited to a 1" propeller shaft. The plans called for strut item 90-132 but that specific item number is apparently no longer available. After conferring with Glen-L by phone/e-mail, and 90-116 seemed to do the trick. As you know, the plans call for 1" propeller shaft and a 1 1/8" rudder shaft and I saw no particular reason to beef up either beyond the spec. I too am assuming a 300HP small block and did speak with the local Mercruiser dealer before taking the $320 plunge for the strut and he concurred that a 1" propeller shaft, given the expected boat weight, length, etc would be ideal.

Hope that helps in some small way.

Donn

TomB
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Re: Tahoe 23 Prop Shaft Diameter?

Post by TomB » Wed Aug 15, 2018 1:22 pm

Thanks for the recommendation Ken. I plan to install a 1” prop shaft.

Donn, Thanks it alway helps to see how others approached the same issue. Spiling is fun (I probably need one of those canvas shop coats with the rap around arms and lots of buckles :shock: ). I like seeing the boards shaped into the sweep the hull requires. I hope I left enough rise in the lines at the bow so it looks like the boat has its chin up.

In trying to find a 14* prop strut and a 14* shaft log, I am learning it ain’t as simple as this prop strut or that prop strut. I see that a strut with a barrel ID of 1 1/4” up to 2” can all carry a 1” prop shaft, except 1 3/4”, by changing the strut bearing. Some think the bearing wall should be about 1/4 of the shaft diameter, so that would suggest I look for a strut with a 1 1/2” bore size. Then there’s the drop from keel to shaft center line. Too low a drop and the prop wash scours the underside of the hull. Too much drop and say good bye to the prop in shallow water (seems like I saw something about reduced prop effectiveness because of lost proximity to the hull too) And the angle, is 14* 14* or is it about 14*, maybe 13* to 15*? I am waiting to hear back about a 13* shaft log and 13* strut with a 1 5/8” bore and a 7 13/16” drop. The bore/drop combination gives me good space for a 13” prop and room enough to go with a bigger shaft if I somehow wind up with a huge motor. Since it is slightly flatter it may push the motor forward. To far? I will draw a cross section if the parts are available.

Tom

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kens
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Re: Tahoe 23 Prop Shaft Diameter?

Post by kens » Thu Aug 16, 2018 3:06 am

I scratched my head for all those dimensions on my build also.
I ended up with a piece of 2x8, and drilled for the strut/rudder/shaft log so that I could actually 'eyeball' it.
I hear some guys shim or fair the strut to get exact.
If you got the shaft log with the rubber hose holding the stuffing box, you get some leeway in the rubber hose.
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

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Roberta
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Re: Tahoe 23 Prop Shaft Diameter?

Post by Roberta » Thu Aug 16, 2018 5:25 am

The strut and shaft log are mounted on the keel and the angles of each need to be close. The rubber hose allows some leeway, like Ken mentioned, so the log should be within 2 deg. of the strut. The keel is generally about 2 deg. different that the motor stringers due to the slope from about frame 4 to the transom and that art of the keel should be and even slope and not arched. I used a 16 deg log and a 16 deg strut.

Ask Gayle at Glen L what parts are available again. Glenwood is now producing parts that were unavailable for a while and may not be back in the Glen L catalog. She can help with getting the right parts and advising on any appropriate substitutions.

On a side not, when building the Torpedo, I set the strut directly to the keel when it was still flat to ensure it was well aligned and the spot was solid. I added a spacer under it to set the height in it's location. I faired the keel around the strut location after the strut was mounted temporarily and planked around it. It was easier to do than to try and sand a flat spot for the strut after the hull was planked.
Attachments
Planking near done 010.JPG
Planking near done 009.JPG
intake piping 001.JPG
prop shaft 001.JPG
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

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Roberta
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Re: Tahoe 23 Prop Shaft Diameter?

Post by Roberta » Thu Aug 16, 2018 5:48 am

The parts I used on the Torpedo were:

Strut: 16 deg. 90-122
Shaft log: 16 deg. Came from Marine Hardware (through Glen L) SHLG16/150B Current Glen L number is 90-195
Prop Shaft Stuffing Box: 1" 90-223
Shaft Log Stuffing Box Hose: 1-3/4" 90-232
Rudder Stuffing Box: 1-1/8" 90-101
Rudder Stuffing Box Plate: 4x4" 90-108

Some of these parts may not appear in the catalog at this time, but I believe Glenwood I making them again. Check with Gayle.

Roberta
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

Hercdrvr
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Re: Tahoe 23 Prop Shaft Diameter?

Post by Hercdrvr » Thu Aug 16, 2018 5:59 am

Roberta,
Nice consolidated list of part numbers, helpful to see all the parts needed. I took a picture.
Matt B

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Roberta
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Re: Tahoe 23 Prop Shaft Diameter?

Post by Roberta » Thu Aug 16, 2018 6:08 am

Looking back through my invoices I needed to make some edits to sizes and part numbers. The above is now correct. Again, Gayle was able to provide all the necessary stuff I needed. Check with her first as she has first hand knowledge of the proper gear for the boats and what is safely substituted.

Roberta :D
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

TomB
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Re: Tahoe 23 Prop Shaft Diameter?

Post by TomB » Thu Aug 16, 2018 6:35 am

Thanks for the encouragement Ken and Roberta, I need it. I am an ENGINEER, including all the attributes, positive and negative. Now I’m an expert on prop struts for the next week or so until my short-term memory…

I apparently hit this at just the wrong time for Glenwood. The inboard hardware listed in the instructions, rudder, post bracket, prop strut haven’t been available (I didn’t learn the why). I wound up with Buck Algonquin rudder parts and am waiting to hear back from them on prop strut/shaft log mentioned in an earlier post. I called Glenwood a bunch of times over the last few days and left messages, still waiting. I learned yesterday that Glenwood hit some kind of business speed bump early in the year and may be back on track. What I haven’t done is call Gayle. I will fix that this morning.

I like the idea of getting the holes out of the way before planking but didn’t have the nerve. Now I’m in the “you’ve put it off as long as you can” phase and most variables have been worked out. So the plan is to drill the holes now and then put on the final bottom layer.

Stay tuned,

Tom

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Roberta
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Re: Tahoe 23 Prop Shaft Diameter?

Post by Roberta » Thu Aug 16, 2018 7:07 am

You probably would be OK with the 90-140 (16 deg) strut and the 90-195 shaft log. Both of those have very big mounting surfaces and are very strong. The strut is the same as mine except the drop is a 3/4" less. You would still be OK with a 12 or 13 inch prop. I think these are readily available.

Roberta
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

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