My opinion based on personal experience.
- generally good engines but they gouge terribly on parts. If I repower
will NOT be a Westerbeke.
Volvo - had an MD17C years ago that I loved. Have heard a few complaints about QC in recent years. And Sanibel Sailor put it well. Volvo parts prices make Westerbeke look cheap
Beta (marinized Kubota) - so far have never heard a complaint about engine quality, reliability
and support from the US division. Cannot comment about support elsewhere. Parts are very reasonable and other than the marine
specific parts (heat exchangers, raw water
pumps, manifolds, etc) can be purchased from any Kubota tractor dealer.
Yanmar. Never owned one but had many friends with Yanmars. Older ones I never heard a complaint. Newer ones I hear a few. I have read a number of complaints that parts distribution is controlled and restricted to force you to buy from the local, authorized source ONLY. I have trouble supporting that kind of business model for something I buy.\
. Used to be one of the tops for small boat engines. Not sure where they stand these days.