Prop shaft alignment?

[John Denney]

Hi all, I have nearly finished painting the hull and I am turning my attention to the oily bits.
I have managed to refurbish the combi unit and I have noticed that the control tube is slightly worn (on one side only - which is a bit weird?) where it contacts the stern bearing. It really is not bad at all but I am surprised to find any. I believe the control tube has been replaced (I found the old one and it was also worn (badly)) in the same spot.
Why do they wear here when they sit in a nylon bearing - I would imagine the the nylon bearing would wear away long before the stainless steel tube would?
Also, I was wondering how to ensure that the control tube / prop shaft is aligned correctly with the engine...... I assume the engine sits on rubber mounts and that they will be worn by now. Basically I just want to ensure that when I have replaced all the bearings and seals at the back end that the engine does not wobble about and wear them all out again because it is not aligned properly. Is it easy to check?

Thanks in advance....
John

 

[johnadenney]

Sorry forgot to mention... Volvo MD6 a and standard combi arrangement.

 

[tiempo2010]

You should probably replace the engine mounts if they are very old.

 

[johnadenney]

Are the engine mounts still available to buy - if so - where from?

 

[tiempo2010]

Yes, this is just one example:

Inboard Engine Mounts for Sale at Go2marine

Inboard Engine Mounts control vibration and keep your engine securely in place allowing the power to get where it's supposed to - to your prop shaft or outdrive. Find the right engine mount for your boat from Barr Marine, PYI or Bushings Inc.

www.go2marine.com

 

[johnadenney]

Many thanks Brian... is it tricky to get the engine lined up
properly? I have read how it is done with a "normal" set up but my
Vega has the Combi unit and I cannot fathom out how to check the
alignment after fitting new engine mounts. Anyone done it?
Many thanks for all the helpful advice.

I have painted the topsides and the hull has been primed. Pics at...
farmer boy all in reverse order so it
get worse as you go though them!

John

 

[tiempo2010]

John

I don't have a Vega or a combi and I haven't seen one.

Regardless the engine bolts to a flat face which in a normal drive system
is a coupling on the drive shaft. This is where the measurement of
alignment takes place with a feeler gauge.

When replacing mounts measure the old ones before removal, from the surface
of the bearer to the top of the nut the engine rests on. Adjust the new
ones to this measurement as it should put you in the ballpark.

 

[johnadenney]

Sorry Brian - forgot you don't have a Vega! There is not a flange
exactly... the prop shaft and control tube just disappear into the
back of the combi... hoping someone knows what I need to do....

 

[pjacobs55]

Nice job, John. You must be working like a mad man! Did you spray the topsides? Looks really good.

Peter
#1331 'Sin Tacha'

 

[johnadenney]

Thankyou - I am trying to get as much done as possible ready for a
trip to the Isle of Man at the beginning of April. Still loads to
do! I ended up painting it by hand.. I have never done it before and
I was surprised how good the result is (although the pics are
flattering!) I think the paint is designed to flow so the brush marks
disappear. I wish I had tipped out and rubbed down the undercoat
now.. it would have been a really good finish then...

I have yet to put the combi unit / control tube back in (can't seem to
get any info on alignment yet), fit the new bow roller, Navik, new
sprayhood and all the inside needs a good tidy up!

Just a thought - I get the impression that the combi unit does not
have a neutral as such... am I right in assuming that the prop keeps
turning as long as the engine is? Does this cause any problems with
rubbish around the prop (no room for a rope cutter and you need to
stop the engine quick if you get a tangle?) and I guess, if I am
charging batteries regularly then the prop shaft will be turning all
the time... if so that may explain why the stern bearing and control
tube are showing signs of a bit of wear...I have got the antifoul on now..http://www.flickr.com/photos/58818786@N04/Thanks for your kind comments

John

 

[johnadenney]

sorry - that was a bad link try...

www.flickr.com/photos/58818786@N04/

 

[Vega1447]

Yes. The fact that the prop is always turning is IMO a major weakness of the Combi setup.
I take a lot of precautions when coming alongside/leaving pontoon - floating nylon stern line being the most important.
I replace it by a heavy line when boat is tied up.

Of course none of this protects against picking up floating debris.

Vigilance is the price of Trouble-Free Motoring....

John V1447 Breakaway

John Kinsella
Mathematics and Statistics Dept
University of Limerick

Phone 0035361202148
Web jkcray.maths.ul.ie