It is too bad that just about every boat I have ever seen built prior to 1990 has had to have it's fuel system " cobbled" up with those horrible aftermarket Racor filters... or do you not have one of those cobbled up boats?
HOLLYWOOD
Major big difference between installing a newer stand-alone fuel filter and having to have an actual core engine component machined because it takes too long to get the proper part. Or it's become impossible to get the part.
Your analogy between Boeing and marine engines is meaningless because while we are constantly improving our products and designing and making new components, WE'RE doing that, not our customers. Our customers don't see or have to do any of this. They simply get the new component and install it. If they had to design and fabricate new components to keep their airplanes operating (outside of the engines which we have no responsibility for) because we no longer supported them Airbus would have a whole lot of new customers.
We boaters are the equivalent of the customer. If an engine manufacturer or an aftermarket supplier can't supply what's needed in terms of engine core components, I'm going to get rid of the engine. And by the same token, if a manufacturer or aftermarket supplier no longer supports a certain engine I'd be a real dumb-ass to buy a boat with that engine, wouldn't I?
The only reason the Ford Lehman engines are still viable is because of the aftermarket support they have. You can get rings, valves, valve guides, injection pump overhauls, etc, etc, etc from suppliers other than Ford of England who stopped giving a crap about these engines decades ago.
But if our engines fail in a way that is not supported by the aftermarket folks and requires having core components custom machined then the Lehmans are coming out of the boat and going into the dumpster and new engines are going in.
We're not talking about keeping some historical artifact running here, like an Atlas or a Washington where fabricating parts is the only option to keeping these museum pieces running. We're talking about a 1950s era tractor engine that is easily replaced. Custom-machining core components for these things is just dumb as far as I'm concerned.
Volvo marine diesels are excellent powerplants. There seems to be little argument on that and my own limited experience with them in Hawaii bears that out. But from an awful lot of customer testimonials Volvo engines-- at least the older ones-- have spotty manufacturer support and parts can be extremely time consuming and expensive to get. So it's a no-brainier to me to simply not buy a boat with Volvo engines. There are too many good boats out there to have to settle for something that requires you to hire Acme Machining in order to keep it running.