Hi Graham

I’ve installed a Raymarine Evolution on my Wight a few years ago after ripping out the remains of what must have been the original C1970’s system (called a “Space Age Automatic Pilot”!). I’ve therefore not had direct experience of the Mk1 but I understand that the Evolution system uses the Mk2 wheel. Checking I see the differences between Mk1 Wheel (black) and the Mk2 (grey ) are:

• The Mk1 has a black wheel drive ring and is compatible with the 4000+ control head1. Also, the older ST4000 control head can work with the Mk1 wheel unit. Users have reported that the Mk1 system works well, but any slight connection fault in any part of the system (including the motor) can disrupt its performance.
• Mk2 is grey and can also function with the 4000+ control head. If you have an older ST4000 control head, it should work fine with the Mk2 wheel unit as well. The Mk2 Wheel Drive unit clamps directly to your boat’s steering wheel, making installation straightforward. It features an adjustable clutch lever for switching between autopilot control and hand-steering2

In summary, I guess it comes down to your control head – both wheel units are interchangeable and can work with the 4000+ control head and if you have the older ST4000 control head, it should also be compatible.

The references I used to get this info were :

1. https://forums.ybw.com/threads/raymarine-wheel-pilot-mk1-vs-mk2.586536/
2. https://forums.ybw.com/threads/autohelm-raymarine-autopilot-belts-ah4000-st4000mk1-and-st4000mk2.410407/
3. https://www.raymarine.co.uk/en-gb/our-products/boat-autopilots/autopilot-drive-units/cockpit-mk-ii-wheel-drive
4. https://www.raymarine.com/en-us/learning/online-guides/what-are-the-different-types-of-boat-autopilot

You mentioned compatibility with the compass. That’ll be a Raymarine Flux Compass presumably which connects the the control head (via one of the SeaTalk network options). The compass operates independently of the wheel unit. It continuously provides heading information (magnetic or gyroscopic) to the autopilot system. The autopilot uses this data to maintain the desired course.Both the Mk1 and Mk2 wheel units are designed to work with the Raymarine autopilot systems. They connect to the control head and drive the steering mechanism. As long as the wheel unit is properly installed and compatible with your autopilot system, it should not affect the compass.

But don’t expect complete compatibility. When you change the wheel unit, ensure that the compass calibration remains accurate. Follow Raymarine’s guidelines for compass calibration and alignment to ensure that the autopilot responds correctly to the compass data. So after changing the wheel unit, perform the usual “sea trial” to verify that the autopilot maintains the correct course, i.e.: monitor the compass readings during 360degree turns, changes in speed, etc. to ensure consistency. Note the manual says all such turns should be done at a min boat speed of 3kts.

I keep by Raymarine manual handy, but I must say they’re not overly detailed. I use the Evolution manual but it sounds like you’d need the Raymarine 4000 Mk2 Service Manual (which covers the Raymarine 4000 Mk2 wheel drive unit) (see here: https://www.manualslib.com/manual/3358595/Raymarine-4000-Mk2.html) or the ST4000 Operating and Installation Manual (which specifically covers the ST4000 wheel drive autopilot and contains information for both Mk1 and Mk2 wheel units) (see here: https://www.manualslib.com/manual/313996/Raymarine-St4000.html)

Last thing to note. My Raymarine Evolution system behaved like a drunken cow when I first installed it – reeling from port to starboard, being late to turn and then overcorrecting. Despite fiddling with the settings I couldn’t get the thing to work properly – that is until I fitted a rudder sensor. That changed everything – it now works very acceptably and I can make a cuppa whilst travelling down the river singlehanded. If you’ve already got a rudder sensor then this doesn’t apply, but if not, then I thoroughly recommend it.

All the best and hope this helps

Rob Wombwell