I went from 454/330 old on one side to 540 hp on the other side for 5 years (until the other 454 quit), only difference was throttling, had to make sure rpms matched, not throttle levers. The throttle on the new was about 1/2 position of the old at exact rpms.

That would drive me crazy, like one clean sock and one dirty sock.

J607 is pretty old, I think most guys would be using J1349 as the accepted standard these days. There's lots of other correction factors too. My numbers are from standard J1349 with a weather station, and the correction factor on my dyno is usually around 1.02 or less so there's not much there anyway. The engines are also fully rigged, running all accessories and full wet exhaust.

Not really so bad, if the dirty sock is just a little bit dirty, but the dirty sock is like stepping into a bucket of poop so you got no choice but to change it. I could have rebuilt of both at the time, but I chose to significantly up the anti on them such that what I put into the new engine would have paid for rebuilding both old engines to stock level power.

So that would mean all the 8.2 Mag and 8.2 Mag HO are not assembled by GM?

The new Mercruiser/Mercury 8.2Mag and 8.2HO engines are Mercury buillt product from what I understand and are built in Fondulac. I had heard that Mercury was subcontracting the short blocks though and I have not been able to confirm that. In any event they are not assembled by the subcontractors that are now doing the GM crate engine programs and apparently their are several different firms doing this work.
Maybe someone here on OSO can check their Mercury sources and confirm this.

Best Regards,
Ray @ Raylar

So, the new 8.2s are technically "hand assembled" by Mercury instead of being purchased as a short block?

i have heard of people with a 318 dodge on one side and 454 on the other. of course, this was in a sportfish that only had to outrun the fish. but if you keep it geared and propped the same both sides, no issues. you could probably do a little cable adjusting for lever pos at cruise.

I purchased 2 two years ago and took them apart to change cams to RMBUILDER cams. Every bolt inside and outside had different colors of permenant marker. All main bolts had a green slash, rods a red slash and so on.

Crate motors or Mercs?