I don't think anyone has been able to remove them and change the computer program from Merc as of yet, I may be wrong but mu buddy has two of these engines and if they did come up with something he would have it. I know he has spoke to several compaines asking when? they said it will take time to get around the computer.

No.

All black merc's are rated a the prop shaft since the mid 80's at least, and all merc racing are rated at the flywheel after the introduction of the 600sci.

Thats what I thought ,but by reading this http://www.fullthrottlemarine.com/ ( left side ,vieuw our high perf projects) it let me believe that the output is crank rated ?
Or his dyno must be off ,but I found that hard to believe.

Very interesting reading for sure. The thing is. If you ask mercuiser, they will say it is prop hp. If you go to merc's website, they clearly state it is @ prop. Just cheked with the new 8,2. When you test the engine in the boat like that, there are a few variables. Engine and drive hours, air temp and humidity, drive oil ect. Now it gets interesting. If you go to merc racing's website, they have changed the rating on the 1100 and 1350 to transmission rating, It said crank shaft rating a month ago! The 1200 is still rated at the crank, thay claim. Confused? I honestly think they will change thier claims as they see fit. What you need to do, is to take a new engine/drive and replicate mercs testing to the smallest detail.

Another way of looking at it is. If the 425 is crank and the 8,2 is prop, the speed diff, would be rather noticable, but it is not. If the 8,2 is 430 prop, it should about 465-470 at the crank. That is a big difference. I asked formula about this some time ago, and they said, there where no difference on a 350ss with a set of 496HO's and the same boat with 8,2HO's. I would say that, a combined increase in hp of about 130 to 140 hp would be felt.

My bottom line is. I just don't think mercury is very accurate or maybe even honest about the hp claims.

Isn't the new 502 just a de tuned 525 I think? There is alot of power that can be made with this engine!

For accuracy in temp/humidity ,that should be taken care of using a correction table wich measures temperature and humidity and should be equal everywhere on earth.
My friend has 2 Superflow dyno,s ,using corrected horsepower ,he calibrate his dyno very often, cause he does use his dyno,s almost every day ,he received a new mercruiser engine from a P1 team that needs to be verified in Horsepower /torque ,the power was within 3 HP from what Mercury dyno,d ,so I guess they are pretty accured.
I don,t know what mercury said about prop or crank,cause I couldn,t find it on their website ..

Is Merc using any O2 sensor feedback on these engines yet?

Yes i think that is where the issue is. I also think they have two on each cat one before and one after. That is where the aftermarket companies are having trouble, getting around those. But I will say and it could be the boat, Matt's 32 Sunsation runs in the low 90's with those motors.

CMI already offers aftermarket headers for the 8.2 with catalytic converters so they are just a bolt on. It is just a matter of time before someone gets into the computer.

If you are truly looking at a boat, just pay the money for the 525's - It just isnt worth fooling with the 8.2's. By the time the warranty is up, someone will be into the computers anyway...

A picture of the 502's & the boat (It is for sale):coolcowboy: If your looking