Raymarine EV-100 wheel autohelm assembly problem

[Adam Turner]

Hi all,

I went out in a strong breeze and my Raymarine EV-100 wheel autohelm couldn't keep me pointed into wind. After struggling to hoist my sails and wrestle the wheel I looked down to find the autohelm assembly had popped open, basically into two halves.

A number of bearings had been lost and these are now replaced, but I'm having difficulty reassembling the two halves, marked A and B in the images.

If I invert A and try to slide it down onto B, the ball bearings fall out.

If I invert B, then I can't access the belt to stretch it over the black wheel.

If I de-tension the belt by removing it from the gear assembly, then once the two halves are together I can't access the allen screws to reassemble the gear assembly.

Has anyone managed this reassembly? If so, advice welcomed.

{Internet research suggests the design has been altered on the most recent versions (mine's from 2022), with the bearing and black wheel swapping halves. However, there are lugs on grey plastic part of A which prove that it's on the correct half.}

Thanks in advance!

[Yngmar]

An old mechanic's trick is to stick the bearing balls on with a blob of grease, holding them long enough for assembly. Worth a try perhaps.

[Adam Turner]

Thanks Yngmar,

That thought briefly occurred to me but grease etc. is expressly counter-indicated (see pic). I assume because rotation would make it spread inside the assembly, which would lead to belt slippage.

Popping open under strain is apparently something that happens with these units, so hopefully someone out there has been here before, or knows someone else who has...

[tiger79]

As I understand it, you need to assemble the black wheel on to the main part (part B in your pics).  You can then put the belt on, replace the support plate and fix it with the allen screws, then drop the front plate on top.

Here's the parts diagram for the 4000 Mk2 drive, which is similar.

[Stevie H]

Tiger79 is correct.

I recently stripped my albeit much older wheel drive down and everything should be fitted on the 'back plate' (your Part B) and then the front plate simply fits on top.

[Adam Turner]

Thanks for the responses. The exploded diagram was especially helpful, although I always shudder when I see the word 'simply' in instructions like these

As I pop more of the ball bearings into the race, the assembly centres, until with six bearings to go, I can't lever the race open enough to pop the next one in.

If you look closely at the race in the pic you can see what I mean--it's centred up to a gap that keeps the bearings retained, so it 'shouldn't' be possible to open it.

I've de-tensioned the belt fully.

Anything else I could try before rage-quitting??

[Adam Turner]

Update for interested lurkers

I outsourced the reassembly of the wheel unit.

For reassembly, the trick is to put all the ball bearings into the race, then use thin screwdrivers to position each one in turn underneath the plastic bearing cages (part 10 in the exploded diagram above).

Even after loosening out all tension, to get the belt round the assembly, it was still necessary to leave out one of the clutch rollers (part 5), and even then, the assembly rolled in one direction far more easily than the other.  The conclusion was that the unit had been supplied with a belt that was too short.

This would also be consistent with the assembly 'popping open' as it did.

I had a spare belt, and fitted it to the reassembled unit. Lo and behold, it now rotates smoothly in both directions, and with similar resistance as other units installed on boats in the marina.

Mine is a Mk 2, so perhaps Raymarine had a job lot of Mk 1 belts that they needed to get through in the factory.