Left the exhaust cap off and it rained (3LW)

[MtB]

9 hours ago, David Mack said:

Could 12V on a 24V starter motor also mean the solenoid which pushes the pinion into gear doesn't push it all the way, hence the teeth not engaging every time?

 

I think this is a good point. The failure of the pinion to reliably engage in the ring gear is another indication this might be a 24V motor on a 12V battery.

 

Possibly another way to distinguish a 12V motor from a 24V motor is to measure the resistance of the solenoid coil. The 12V coil will be lower than a 24V coil. I'll measure mine (known to be 24V) next time I'm on the boat. 

[Ben Jameson]

9 hours ago, agg221 said:

Ref. confirming 12V vs. 24V, sometimes there is a data plate on the starter motor, on the same face as the connecting terminals. Mine was missing. My approach to confirming it was 24V wasn't very scientific. I borrowed a second starter battery and a wire and temporarily wired it in series. My reckoning was that I knew the engine was good, so it was either a faulty starter motor, in which case cooking it at 24V wouldn't make it much worse as it would need to go off for repair anyway; or it would work properly and prove the point. It did the latter.

 

No idea on the electrical charging side I'm afraid. @Ben Jameson has a 24V starter and may be able to comment on the wiring.

 

We've got two battery banks, 12V (5 batteries in parallel) for domestic and 24V (2 batteries in series) feeding the CAV starter. We have a 12V alternator and 12V Victron mains charger which charge the banks via a split charge relay and, in the case of the 24V bank, via a Victron DC-DC converter that steps the voltage up (examples at https://www.victronenergy.com/dc-dc-converters).

 

Ben.

[jonesthenuke]

Noting the poor engagement of the starter pinion with the flywheel gear, it's my understanding that the starter should not spin until engaged with the flywheel (the rotor moves axially and closes the main power contacts).  Looking at the images I wonder if the starter is not in the correct position, specifically that it should be moved towards the flywheel. The clamp only wraps around the starter so does not locate it in a particular axial position. Is there any way to look inside the flywheel housing to see the position of the starter pinion? If you need a starter motor manual I have a pdf copy somewhere.

Edited May 15 by jonesthenuke

[bigoltubosteel]

Thanks for all the information everyone. I will see if I can find any identification on the starter when next down at the boat, might be lunchtime today or tomorrow but latest the weekend.

 

Someone else noticed that the starter was moving a little when being started and I tightened that strap which helped but maybe it's still not quite in the right position, if you look at the side shot, it doesn't look like the end of the starter is quite aligned with the entrance to the flywheel:

 

 

I'm not sure it's possible/practical to get in to the housing to have a look but it's not something I have tried to look into before, so will have a look and see if there is a way.

[bigoltubosteel]

No sign of any plate or obvious voltage reference just a lot of carbon (?) dust. There is a number inside but that's probably a casting number, right?

[MtB]

58 minutes ago, bigoltubosteel said:

No sign of any plate or obvious voltage reference just a lot of carbon (?) dust. There is a number inside but that's probably a casting number, right?

 

 

What value resistance do you get on the solenoid coil? 

 

Measure between (probably) that red wire and the starter body. 

 

 

 

[BEngo]

On 15/05/2025 at 09:32, jonesthenuke said:

it's my understanding that the starter should not spin until engaged with the flywheel (the rotor moves axially and closes the main power contacts).

This is correct, as far as it goes, but a little more happens.

 

   When the solenoid closes the initial contacts the magnetic field causes two things to happen :

the armature is drawn further into the stator, as it does so

the armature  revolves slowly, in order to help engagement.

 

In the last stage of engagement the rotor mechanically closes the main contacts and the armature spins at full power.

If the armature does not get all the way forward, the contacts will not fully close, leading to low power and burning of the contacts.

 

There should be a gap of 9/64 in between the  face of the pinion and the face of the ring gear, to allow all this to happen.

 

Somewhere I have the Workshop manual for the CAV BS5  and BS6 starters.

 

The pictured commutator could do with a good clean, ( rag and meths,fine sandpaper if you must;  never emery or wet and dry) and it has a few ridges which would helpfully be skimmed off.

 

The brushes also need a looking  at- they are under the  hooked end of the curly spring near the long edge of the end casting.

 

N

[bigoltubosteel]

44 minutes ago, MtB said:

 

 

What value resistance do you get on the solenoid coil? 

 

Measure between (probably) that red wire and the starter body. 

 

 

 

If I'm doing it right (a little out of my depth) it stabilises around 5 ohm

[MtB]

7 minutes ago, bigoltubosteel said:

If I'm doing it right (a little out of my depth) it stabilises around 5 ohm

 

Hmm sounds a credible reading. A little high if anything though so this also points to this being a 24V starter.

 

[BEngo]

Here is the workshop manual 

 

N

CAV Axial Sarters WM_250517_190814.pdf

[billh]

The starter information label should be on the outside  front of the plate between the two large terminals .It may have 12v  or 24v embossed on a lilttle insulated panel at the terminals in  rather small characters. Also, check the connection between the copper bus bar and the back of the main terminals, round brass thing with bar slotted into it . Had one go faulty with loose connection, cured by soldering with a big iron.

 

[MtB]

On 17/05/2025 at 18:32, bigoltubosteel said:

If I'm doing it right (a little out of my depth) it stabilises around 5 ohm

 

I've just measured my 24V starter and the solenoid resistance is 8 Ohms. 

Or 7.7 Ohms being particularly careful to get good contacts! 

 

 

 

[bigoltubosteel]

So a lot more, therefore I might just have a struggling 12V? It does need a good clean and there could just be wear going on.

[matty40s]

Apparently, all the hysteric boats at Crick show had a big engine start up yesterday afternoon about 3.30. 

One (forum member) had forgotten to cover the exhaust up overnight, and splattered the boat next to it whilst showing off!!!

Didnt they....

[bigoltubosteel]

Finally got around to pulling the starter out and confirmed 12V