Hi Ian,



Very interested in you mods to Bowthruster gearbox. Despite changing
all my bearings and seals the water still gets in and I think that the
stainless steel sleeve on the prop drive shaft is the answer.



I would therefore be grateful if you could e-mail the exact o/d of
your sleeve to suit the seal i/d if you have a note of this size.



Maybe then I can stop waking up everyone in the Marina every time I
leave !



Regards,



Malcolm S/M 464 Bon Jovi.



From: amelyachtowners@...
<mailto:amelyachtowners%40yahoogroups.com>
[mailto:amelyachtowners@...
<mailto:amelyachtowners%40yahoogroups.com>] On Behalf Of Ian Shepherd
Sent: 27 July 2010 16:39
To: amelyachtowners@...
<mailto:amelyachtowners%40yahoogroups.com>
Subject: Re: [Amel] Modifications





Hi Richard,

I am not sure if I mentioned that the stainless prop shaft bush has been
in use for over three years with no signs of any adverse effect.

Regards

Ian SM 414 Crusader

On 02/07/2010 14:13, Richard03801 wrote:

Thanks for the info. One question how much clearance did you plan
between the shaft and bushings? Metal to metal ss to ss normally does
not work well. If they touch they will Gaul as the bronze is used as a
bearing surface. It may be that the bearing pack is stiff enough to
hold the shaft from moving/touching. I guess time will tell.
Regards
Sent by Richard Piller

On Jul 1, 2010, at 5:55 PM, Ian Shepherd <sv_freespirit@...

<mailto:sv_freespirit%40yahoo.co.uk> <mailto:sv_freespirit%40yahoo.co.uk>

<mailto:sv_freespirit%40yahoo.co.uk>> wrote:

I read recently that owners modifications can be detrimental to the
original concept. Maybe so, but here are three modifications that have
definitely improved my boat.

Three and a half years ago I replaced the bronze main engine prop

shaft

bush with one made of high grade stainless steel. I recently

hauled for

the first time since fitting it and there was absolutely no wear
whatsoever on the bush. Just a very slight polishing of the surface
where the lip seals mate to the bush. There was no noticeable wear to
the seals either after 600 hours of motoring, but I changed them

anyway.

This contrasts markedly to the normal wear experienced on the standard
bush. I believe that the maintenance interval is now much longer with
the stainless bush, and there is a worthwhile long term cost

saving too.

I replaced the 70M of chain supplied by Amel with 90M. There was a
noticeable improvement in the boats motion particularly in short seas.
The boat pitches less, hardly ever slams any more and because of this
maintains a higher average speed. I also have 10M of chain and 100M of
rope for my second anchor stored in the forward locker together

with my

two Fortress anchors, so in reality, I have the equivalent of 100M of
10mm chain in bow. The extra weight forward certainly seems to be for
the better.

I decided to try and improve the lubrication of the bow thruster,

which

seems to have more sea water inside it than oil most of the time. The
arrangement of a single lip seal over a rough fibre shaft is hardly
conducive to keeping the sea water out. I removed the shaft and had it
machined down to accept a thin stainless sleeve for the lip seal

to run

on. I then replaced the three open ball race bearings, which were all
rusty, with sealed bearings running in their own grease. Of course

this

prevents you pouring the oil in via the top of the tube, so I

decided to

not use oil to lubricate the bevel gears, but instead use water
repellent grease.

This was packed into the gearbox housing before the back plate was
refitted, leaving a small gap to allow for expansion, and grease was
also placed between the outside of the outer bearing and the lip seal.
This was done about four months ago, and the bow thruster has never
sounded sweeter. Gone is the awful sound of bearings running is a sea
water emulsion, and there does not seem to be any loss in power

either.

Time will tell, and I shall remove the bow thruster this winter to see
if the modifications have had any adverse effects on the gears, but it
is my guess that the life of the seal, bearings and bevel gears

will be

considerably increased.

As they say, cruising is fixing things on water. Anything that reduces
wear and subsequent failure must be for the better.

Ian Shepherd SM 414 Crusader

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