The Mercury website says the motors will make 600 or 700 H.P. no matter the altitude or temperature. I'm wondering if anyone has actually tested that. I've got a trip to Lake Tahoe(6200') planned next month and I'm wondering if I won't need to prop down a couple pitches like I normally do. I'm running a single Mercury 600.

Nobody?

I have 600's but I run in the Atlantic, sorry no help, BUT you might want to take an extra prop, ( I always take extra props when we go on vacation) or 2 that has less pitch just in case your 600 struggles at that altitude...

You might have to, if you had carbs I'd say yes along with jetting. You should call Teague Custom Marine. I know Bob can quickly tell you what set up you need to have for that lake or if your current one is ok.

You won't be as behind as an NA engine but you still will likely lose a noticeable amount of power. If you asked 1350s or another turbo model, then you're likely to be not far behind in power.