Then you (the boaters) and the small manfacturers need to lobby the CARB/EPA so that emissions credits are a free market not an in-house stitch up. I'm sure that it would be very easy to make a case of anit-competitive practices by the large marinisers and the representatives of the authorities.
All you're talking about is making credits tradeable. However, what price the OEMs would charge for them would be up to the market or have to be legislated for.
It does seem highly anti-competitive and appears to quite deliberately attempt to sew up the performance aftermarket to Mercury's own in house racing department. Surely you have anti-trust laws that could challenge this.
Again though this is the framing of the laws rather than the emissions reductions themselves that are the problem. Once cats are available and developed eg the INDMAR solution, those parts could be bought off the shelf as a pattern part.
Look at cars: a few years ago, you had to buy replacment cats from the OEM at great cost, now you can get them anywhere. And buy racing ones with low cell densities. You can buy pretty much anything you want. This has taken time to emerge and I imagine performance boating will take the same path.
There's a business model for you: marine cat company, selling aftermarket exhaust systems that fit SBCs and BBCs and can be used on most systems with a variety of cell densities to suit different powe applications. The regs are such that as long as the thing runs closed loop lambda =1 most of the time (when not at full load), then it should pass emissions tests. Get them certified on stock engines and away you go. Essentially, take a metallic auto monolith and marinise it, add a header and a water dam and a couple of bosses for HEGO sensors and you're away.
Yes I'm making it sound easy and it isn't totally simple but there's a business model there for someone..... If Mercury Racing tie it all up, who else are you going to get your performance cats from? You'll need the cats so you don't need their emissions credits! Better buy those aftermarket performance marinised cats then, it's your only choice!
Apologies for relentness cheerfulness, the sun's shining. In England. In winter. Unusual I know!