Ee gads - new prop shaft time!

[MagicalArmchair]

I ordered a new Flexofold two bladed affair from Denmark, and after sending them the measurements from the shaft, they sent me an ISO 25 prop and hub back. That hub did not fit, so I sent them the hub plus my old propeller and nut back. Turns out my old prop was only connected to the cone by about 25% and my shaft must be non standard . So, time to rip out the prop shaft and replace with another.

I have a Volve Penta Dripless shaft seal, which I fitted with my late father (a shipwright of awesome calibre, needless to say, I am not (yet)) a couple of years ago. I still have the sleeve to protect the lip seals, so, the process would be:

• Put the sleeve on the stern gland to protect its lip seals.
• Split the shaft from the gearbox by undoing the grub nuts holding it on (I seem to remember).
• Slide the sucker out.
• Take opportunity to check out and service the Seal (praps buy a new one, its got to be four years old - this feels a bit wasteful though as I bet its got another 5 years life in it?)
• Replace with ISO 25 shaft cut to length (angle grinder? hacksaw? light sabre?).

So, questions for the panel of the great:

• Have I missed anything about the shaft removal/replacement process?
• Do those grub nuts get done up to a specific torque on refitting?
• Do we think I should replace the seal at the same time? Is there a non burp alternative???? (How I do love hanging upside down in a cockpit locker every time we launch...)

edit - I do need to confirm what my current shaft is mind you - the below would suggest its 25mm, however, I am suspicious it is actually 1 inch... (my 25mm prop anode was far too tight last year, and a wee bit gappy). edit 2 - I suppose if I change the diameter it will mean a new cutlass bearing too...

 

[Tranona]

Definitely check whether it is 25mm or 1" as the two are not interchangeable. If it is 1" then the taper will be almost certainly 1:12 rather than 1:10 if it is a metric shaft (maybe this is your problem in the first place if you have got a 1:10 prop!). The problem with your anode strongly indicates that you have a 1" shaft (25.4mm) as a 25mm anode would not fit properly - as you have discovered.

If you do want to change from a 1" to a 25mm it will mean new coupling, seal and cutless. If the shaft is in good condition it makes sense to get the new prop to match the existing shaft. It makes no difference to the prop other than the taper and the supplier will supply either.

So first measure the existing shaft accurately and go from there.

 

[MagicalArmchair]

Thanks Tranona, If you look at the below, it shows the shaft just for'ard of the cutlass bearing is 25.01mm - indicating it is 25mm, and a long way off 25.4mm

I will measure the shaft at a number of points along its length to confirm that is the case. I will also check for play in the cutlass bearing anyway as its been in there for quite some years!

Anyone have any tips re the stern gland? Any 'non' burp varieties that won't bankrupt me?

 

[pvb]

Anyone have any tips re the stern gland? Any 'non' burp varieties that won't bankrupt me?

Yes, the Radice seal fits the bill.

 

[MagicalArmchair]

Okay, I think my calliper was not configured correctly. See the below - What spec would you suggest my shaft is?

edit: standard IMP 1:12 after the vs.

Top of taper = 25.39mm (corrected) (0.99 inch) vs 1 inch (0.01 inch difference)
Bottom of taper = 21.37mm (0.84 inch) vs 0.823 inch (0.02 inch difference)
Taper length = 51.97mm (2.05 inch) vs 2.125 inch (0.0525 inch difference)
Keyway length = 39.39mm (1.55 inch)
Width of keyway = 5.34mm (0.21 inch) vs 0.25 inch (0.04 inch difference)

Edit: Based around this (http://www.tnorrismarine.co.uk/wp-content/uploads/2014/07/Taper-Dimensions.1.pdf) it looks like a standard imperial 1 inch shaft with a few minor differences (which could be cack handed measuring, or a custom/OEM shaft...). Do we think I could get away with the standard IMP 1 inch hub from flexofold and not change the shaft?

 

[Tranona]

If my calculator and fingers are correct that is 2.6mm over 52mm which is 20:1. Very odd.

Agree with pvb. Radice seal from Sillette has external greasing point and is cheaper than the equivalent Volvo. Same basic design so interchangeable.

 

[pvb]

Agree with pvb. Radice seal from Sillette has external greasing point and is cheaper than the equivalent Volvo. Same basic design so interchangeable.

But I think the Radice seal is only available in metric sizes, so if the OP now thinks he has an imperial shaft, it won't help.

 

[MagicalArmchair]

Correct, 99% sure its imperial now. I calculated the same 20:1 :ambivalence:

51.97 / (23.99-21.37) = 19.84 ~ 20:1

I'm down to see her on Friday, so will remeasure - likely new shaft to fit the prop then... although are those small differences within tolerance?

 

[vyv_cox]

Dimensions of my 12:1, 1 inch shaft were:

Taper length 56.5 mm
Small end diameter 21 mm
Shaft diameter 25.32 mm

 

[MagicalArmchair]

Thanks vyv (love the website by the way!).

Oh for heavens sake typo - my fault, trying to do this 'day job' thing at the same time. Look at the photographs @)

Top of the taper is 25.39mm (hence the 0.99 of an inch!!) :encouragement:

51.97 / (25.39-21.37) = 12.93 ~ 12:1

So, do we think a standard 1" IMP prop hub will do the trick? No need to pull her apart and do the prop shaft...?

 

[pathfinder]

I replaced a volvo md11c from a 70's boat a few years ago, the prop had to be replaced aswell,when checking the taper I found it to be 20:1 the shaft was definately 25mm.The suppliers of the new prop thought this unusual but when they sent me the prop with the 20:1 taper it was a perfect fit.

 

[Ruffles]

Okay, I think my calliper was not configured correctly....

Time to buy an old fashioned vernier caliper?

 

[MagicalArmchair]

Correct Ruffles - a damn sight cheaper than a new prop shaft... I'm waiting on Flexofold to come back to me to let me know if those sizes (below) are within tolerance of the IMP 1" hub (http://www.flexofold.com/propeller-dimensions/#Hub length, IMP standard)...

Top of taper = 25.39mm (0.99 inch) vs 1 inch (0.01 inch difference)
Bottom of taper = 21.37mm (0.84 inch) vs 0.823 inch (0.02 inch difference)
Taper length = 51.97mm (2.05 inch) vs 2.125 inch (0.0525 inch difference)
Keyway length = 39.39mm (1.55 inch)
Width of keyway = 5.34mm (0.21 inch) vs 0.25 inch (0.04 inch difference)

 

[Tranona]

But I think the Radice seal is only available in metric sizes, so if the OP now thinks he has an imperial shaft, it won't help.

Definitely available in Imperial 1" and 1 1/4" according to Sillette website. Hope so as I am about to replace a 1" Volvo with one.

 

[pvb]

That's good.

 

[MagicalArmchair]

Gosh, £59, that's good value.

(FYI http://www.sillette.co.uk/price_pdf_files/deep_sea_mane_craft_shaft_seal.pdf)

Water fed from where though...?

 

[pvb]

Water fed from where though...?

For slow-speed use, it doesn't have to be water fed. Just put a hose on and take it well above the water line, so the seal can vent itself.

 

[PetiteFleur]

But I think the Radice seal is only available in metric sizes, so if the OP now thinks he has an imperial shaft, it won't help.

No, Radice available in 1" diameter size, just fitted two - one on a friends boat and one on mine when the 8yr old Volvo seal leaked after launch.

 

[pvb]

No, Radice available in 1" diameter size, just fitted two - one on a friends boat and one on mine when the 8yr old Volvo seal leaked after launch.

Yes, Tranona confirmed that earlier.

 

[MagicalArmchair]

Thanks pvb - Does a Yanmar 2GM20 == slow speed?