Stern tube bearings

[Tim Evans_4782]

I seem to wear out my stern tube bush quite quickly and wonder if anyone has a better solution to the bush system. A stainless roller perhaps with a splined shaft would be a possibility. Any thoughts?

[Sea Dog]

I think you're looking at the effect rather than the cause. I'd start by checking security and condition of engine mounts and the alignment. I'm assuming you don't have an issue with water lubricated bearings being dry,since you say it's a recurring issue.

 

ETA the assumption

Edited June 22, 2016 by Sea Dog

[Flyboy]

Fit a Python or Aquadrive coupling.

[trackman]

Definitely get your drive train alignment checked. If the shaft is being pulled off line by misaligned gearbox/engine, that puts excess pressure on the stern gear causing extra wear.

 

Well set up these stern tube arrangements last decades. Our boat is 10 years old with thousands of hours on the engine. I've never even had to repack the stern gland and have only had to tighten the gland slightly a couple of times in all that time.

 

The reason is that our boat has a trad style engine room and there's a cardan shaft under the back cabin floor from gearbox to propshaft. There are two universal joints in the run so no missalignment can affect the stern bearing.

 

In a boat with a more usual modern engine installation, the equivalent effect can be achieved by fitting two universal joints between gearbox and stern tube. Aqua drive and Python drive are two examples of devices that include this sort of arrangement. Fitting one would make the stern gland far less susceptible to misalignment.

 

There may not be enough room in your installation for one of these though. If that's so, you will just have to get the alignment corrected, and have it checked regularly.

[DHutch]

I was going to say, something is going wrong as with normal levels of use it should last the life of the boat or very close to. 50 years or more.

 

Is it a conventional type, with packing and grease? How often do you grease it an how much. Shaft condition? Current life expectancy in days/how's use? Waterway your on? Engine mounts and or coupling type?

 

 

Daniel

[magnetman]

alignment.

 

Maybe put a plummer block between engine and stern tube? My engine (90hp) has a centaflex coupling and a plummer block before the stern tube.

 

I'm not sure if its a good design or not really. I think the python thing might be better but I don't have the room for one anyway.

It was the system on the boat when I got it. I repowered it with a new engine and replaced stern gear but retained the original arrangement of centaflex anf plummbet block as it seems reasonable.

[Bee]

You don't say whether you have any flexible coupling in the drivetrain or what engine. Modern engines (Beta and similar) on flexi mounts will try to rock and move, if you have a rigid drivetrain with no 'give' then the gearbox or stern tube will be trying to hold a few hundred kilos of engine steady, something has to wear and it will-rapidly.