Ken : I believe that most all corporations do as Westerbeke does. Don't think you'll get any "cut-rate" parts for a Yanmar from DEPCO.
A few thoughts
Ron,
yes and no. I just bought a $90 Yanmar pump kit for a customer for $28. If you go OEM Yanmar, you pay thru the nose, if you go original pump manufacturer (in this case Johnson) you get it reasonably. In other cases the you can't get the part from the original mfgr. or can't find out who it is. I don't think Yanmar has a pump it owns rights to and forced Johnson to stop selling -- maybe -- dunno.

Certainly Universal didn't have that arrangement with Oberdorfer.

My understand (no personal history on this) is that Beta MArine is pretty much open source on their engines -- Beta actually tells owners what Kubota block it is, so that they can get Kubota parts.

Would Westerbeke do that?

Anyway, my point (not well articulated) was "don't waste time asking the question -- we already know what the answer will be" -- EVEN if there is an alternative available, a dealer won't tell you.
Cheers,
kk