Canal Boat — January 2018

74 January 2018 Canal Boat canalboat.co.ukcanalboat.co.uk

Alternator relay will provide protection

Servicing stern tube seal

BACK CABIN: EXPERTS

I am considering replacing the Vetus

ZWB stern tube seal on my boat with

either an Eliche Radice seal, or a

Michigan Marine seal. Both of these are much

cheaper than a Vetus seal. Have you heard of

any issues arising from using either one of these

seals? Also I plan to change the seal while afloat.

I will remove the half coupling, slide the shaft

back far enough for clearance to remove seal. I

hope to be able to seal the stern tube from the

weed hatch using Denso tape.

Have I overlooked any possible problems?

GEORGE HUNT

TONY REPLIES: I am far from

convinced that the Cutless type rubber

outboard bearing used with Vetus seals

are a good idea for canal use. We had more than

enough wear on a nice deep clean river so dread

to think what mud slurry will do to the bearing. A

worn bearing will allow the shaft to jump about

and that could cause the seal to leak.

Google could not find Michigan Marine Seal

while the other one looks like a typical packless

seal BUT as in many such seals they are designed

to accept a permanent bleed of lubricating/cooling

water from the engine’s raw water pump. Most

canal boats do not have one so the bleed is often

connected to the side of the weed hatch. This

seems to be effective but may invalidate any

warranty.

If you are thinking about changing it because it

is leaking, are you aware that most if not all Vetus

shaft seals have replaceable seals in the cap that

is secured by screws in the end of the assembly?

If you can find the seal dimensions you will almost

certainly find that a bearing supply specialist like

Bearing Boys or Brummer can supply a new seal

at a fraction of the Vetus cost. An engine that is

badly out of alignment might also cause these

seals to leak because the shaft will press on one

side of the seal and possibly deform the lip.

Have you been regularly squirting a little of

the special grease down the screw hole that is

provided for the purpose? If not try it – it just

might stop the leak. I understand the grease for a

Volvo seal is the same but cheaper.

You may find turning the rudder at right angles

to the boat will allow you to push the shaft back a

few more inches but I can not say if this will give

you enough space to change the seal without

measuring it.

The Cutless type outboard bearing has

horizontal grooves in it that allow water to flow

through the bearing to lubricate it. These will

need blocking and more to the point unblocking

once the job is done. I am not sure if the tape will

stick underwater so it seem it’s a try it and see

situation.

Remember that any burrs or machining on the

shaft will damage the new seal as you slide it on

so cover any with a wrap of packing or masking

tape.

The engine in my narrow boat is a

marinised Mercedes van engine with its

original alternator to charge the starter

battery. This is coupled to a warning light on the

instrument panel. The boat is being refitted to

include an additional alternator to charge the leisure

battery.

As the warning light is crucial to energise the

rotor (field coil) of the alternator does this mean that

an additional warning light needs to be installed

along with an additional battery switch connected to

the new alternator? How is this usually done where

multiple alternators are installed?

STEPHEN JEAVONS

TONY REPLIES: If you use one warning

lamp you risk energisation, charging

and diagnostic problems now or in the

future because you are feeding both alternators’ D+

(warning lamp) terminals from one warning lamp.

Best practice is to use a relay fed from the ignition

switch side of the engine alternator warning lamp to

energise the warning lamp for the new alternator. I

attach a diagram.

Q

Q

A

A

Eliche Radice seal