Yes I believe you are likely correct David, although I haven't compared the rpms of equivalent Volvo
and Yanmars. Made a point with our little Volvo to get a low revving one, ours is governed to max of somewhere around 2,800 rpm
which is, of course, quite low for a reasonably modernish little 2 litre engine.
Probably the most popular engines for commercial vessels here in NZ are Caterpillar and MTU, and Volvo too for the planing lighter boats such as do fishing
have an excellent reputation but, of course, they in recent years went through contortions of combining product range with MTU in much of the world. Not many Cummins or John Deere here.
Don't think Detroit have been particularly well represented out here in recent years so not many in newer boats - just had a look on the local MTU/Detroit distributor's website and they don't seem to even list the venerable Detroits such as the Series 60 and give most space to the MTU side of the family
. That I suspect because the land transport/industrial engine market is very small here but across the Tasman in Australia
that is not the case, of course, with big mining industry, a lot of long haul trucking, etc.