This isn’t a new topic, but I looked for a comparison of mounting issues for deck compasses (Silva/Brunton vs. Richie) to share with a friend, and didn’t see the issues I’ve encountered. Just sharing my experience.
I’ve seen the Silva 70P referred to as the ‘gold standard’ for kayak compasses, and the Richie V527 as a close competitor. For some of us, the choice for which to purchase was made by our kayak’s manufacturer.
If you have a recess molded into your deck for a compass, you need to look closely at the recess and compare it with the compass you are considering. I have both the Brunton 70P (now sold as Silva) in a Wilderness Systems Tempest and the Richie V527 in a Current Designs Prana. The Richie requires a less deep recess, and the larger radius corners on the top plate fit more boats’ recesses. The Richie also has compensation magnets built into it to compensate for magnetic variation. My Brunton cannot be adjusted (maybe the newer Silva branded compasses can be–dunno), and also requires a MUCH deeper deck recess than the Richie. To make the top plate fit the corners of some recesses (e.g., Current Designs), you’ll need to file off the pointy corners on the plate you screw down to your deck, if it would fit the recess.
In my case, the Richie could be mounted in both the Tempest and the Prana, but the Brunton can be only mounted in the Tempest; it CANNOT fit in the Prana’s recess because the recess depth is incompatible. One could cut out a 3/8" or so shim of the proper size with the proper hole, but this exercise would take you away from time in your kayak’s seat, paddling.
My experience with the plastic mount for the compass sphere on the Richie is you need to pay attention to the slot in the plastic base of the sphere and the key in the deck-mount (you have to loosen the ring that seals the o-ring to adjust the angle of the sphere). You need to adjust the sphere in the mount so the compass card is more or less level in the compass sphere. If it’s at too high an angle, the compass card will bind on the inside of the sphere, leaving you with a hood ornament rather than a functional compass.
If you’re using a hole saw to cut a hole in your deck, it really doesn’t matter which compass fits which brand of kayak. If I was in this situation, I would go with the Brunton (Silva) and do the the arithmetic to go from magnetic course to true when reading the compass (-15 degrees in my part of the world). Going on a trip where magnetic variation differs from home is problematic. Readjusting the Richie is not a particularly pleasant experience (oh, and don’t lose that non-magnetic screwdriver you’ll get with the Richie).
While they don’t look as “finished” as a deck-mount compass, the compasses that use shock cord to attach to your deck lines (e.g., the V58) have some advantages. One, if you are practicing assisted rescues, you’re less likely to bugger up the plastic lens on your compass when your rescuer drags your boat up on their deck and rolls it over (because your compass will be farther from the bow). Two, you can put it where you can see it. If you use a deck bag, a compass mounted way up the deck may not be visible to you.
Just a few thoughts.