Old falks help needed. Shaft +stern tube installation

[francot]

Hi Falks, I bought an old steel boat and I'm looking some advice from old fellas who can help me to decide what is the best option.

The stern tube is a difficult one as it has been build 40 years ago and has never been finished. Im looking to install the engine and then i cant find the right bearing as the tube is quite big. What would you to buy for the stern tube prop installation?





Any advice from old and yung fellas is welcome!

Franco

[slug]

Gee There is no reason why you can’t have a bushing made to reconcile the present diameter with your proposed new shaft and cutlass

One thing to consider is future cutlass bearing renewal

You style of imbedded ... one end blind ... cutlass bearing is a pain in the ass to remove

You might ask your local marine engine gang if they have any clever ideas to make future bearing renewal easy

Also be sure that your cutlass is properly water lubricated

Blind Cutlass bearings like yours can burn up in a minute if deprived of adequate water flow

[a64pilot]

I would be tempted to have a few plastic bushings made, a few as I doubt it would cost much and may be prudent to have spares as they may be sacrificial as in one may break once in a while during removal etc.
One way of removing Cutless bearings is to saw them in half after the shaft is removed, if you had a sacrificial plastic bushing no need to be super concerned your not cutting onto the shaft tube
So far I have not had to do that, on mine the fit isn’t that tight.
I assume your tube is not removable? If it’s welded in and removal means cutting it out, then I think a sacrificial bushing is not a bad idea, I would prefer myself to have a removable tube, and perhaps that’s what the builder intended, just didn’t get that far?

[slug]

Plastic is troublesome It is not dimensionally stable ...water and heat ..and it may not withstand future cutlass removal abuse

It’s possible to use high grade plastic with precise machining

Also remember a cutlass must be mechanically restrained

Again plastic complicates this

[RaymondR]

I don't think you have a problem.

Once you decide what size prop shaft you need for the proposed engine you can take the dimensions to the manufacturers of stern bearings for a solution.

On my last boat I used one of the rubber bushes which was moulded inside a glass fibre sleeve. I just machined the glass fibre sleeve to a diameter which allowed it to be fitted into the tube.

[jimbunyard]

Vesconite is available worldwide and is easily machined.

They show stock for 110 x 70 x 1000 mm in at least 6 different locations.

https://www.google.com/search?q=vesc...hrome&ie=UTF-8

[slug]

Originally Posted by jimbunyard

Vesconite is available worldwide and is easily machined.

They show stock for 110 x 70 x 1000 mm in at least 6 different locations.

https://www.google.com/search?q=vesc...hrome&ie=UTF-8

Vesconite is a good choice of plastic is considered

[Emmalina]

Originally Posted by slug

Vesconite is a good choice of plastic is considered

Yup Vesconite or Thordon !

[slug]

The original poster might consult the original build drawing

Many keel cutlass bearings , blind cutlass , are mounted in a separate external cutlass aperture

These are superior

[francot]

Thank you all guys.
As english is my second lenguaje, it took me some time to understund exactly what you ment.

I finally decided wich stern gear system I will use:

https://vetusonline.com/english/bron...in-length.html



Here you can see dimensions.

What Im still not sure is about what to use in between the stern tube and the steel tube.

I see RaymondR as the best solution: "the rubber bushes which was moulded inside a glass fibre sleeve. I just machined the glass fibre sleeve to a diameter which allowed it to be fitted into the tube."

do you reckon a better solution?
and last question: what to put as a seal between the hull and the mounting flange... Any Idea?

Thank you all, you´ve give me a good way to see the solution.


Franco

[francot]

How do you reckon to glue it to the steel?

[francot]

Originally Posted by RaymondR

I don't think you have a problem.

Once you decide what size prop shaft you need for the proposed engine you can take the dimensions to the manufacturers of stern bearings for a solution.

On my last boat I used one of the rubber bushes which was moulded inside a glass fibre sleeve. I just machined the glass fibre sleeve to a diameter which allowed it to be fitted into the tube.

How do you rekon to glue it to the steel?

[francot]

Originally Posted by a64pilot

I would be tempted to have a few plastic bushings made, a few as I doubt it would cost much and may be prudent to have spares as they may be sacrificial as in one may break once in a while during removal etc.
One way of removing Cutless bearings is to saw them in half after the shaft is removed, if you had a sacrificial plastic bushing no need to be super concerned your not cutting onto the shaft tube
So far I have not had to do that, on mine the fit isn’t that tight.
I assume your tube is not removable? If it’s welded in and removal means cutting it out, then I think a sacrificial bushing is not a bad idea, I would prefer myself to have a removable tube, and perhaps that’s what the builder intended, just didn’t get that far?

WHat about refrigerating the plastic ?

[slug]

You might investigate CHOCKFAST

This is a pourable , low exotherm chocking material that is commonly used to fill voids , level engine mounts , mount bearings

Chockfast Diagram

It may be applicable to your project

[Lepke]

Have your shaft alignment perfect before pouring any filler. Small differences in the engine beds and the angle of the existing tube may require the shaft to be off center.