The non-supercharged motors are set up very conservatively. They, "Mercury", is not interested in paying warranty claims and wants to have very reliable motors out in the market. They are sent to the consumer with timing and fuel curves that recommend the use of 87 octane fuel. Increased timing and modified fuel curves allow for output gains with increased octane use.
My personal experience shows that running motors with increased timing, increased boost, 93 octane fuel, and sustained runs, (25 miles at W.O.T.), I would not turn them over 6800. Shorter burst, better fuel, have allowed guys to turn them up into the 7300 range but they won't live long doing that outside of short burst. Rod bolts, head gaskets, rods and stretching head bolts seem to be the first breaking points.

Any modification voids all warranty coverage as it should....

Joe

Sounds like a good way to make the reliable OB into the same thing as a modified BBC. Just much easier to replace and work on.

I had 400 hours on my powerhead and it was fine. We ran a 139 pass at the shootout and decided to swing for the fence with nitrous in order to run with Justin and Warren but the rods didn't agree. I plan to run motec on the new boat but I will have good internals before it gets turned up beyond the numbers that I mentioned.

Joe

Just curious if you don't mind sharing, but what's the bill for that meltdown?

Mine was extreme. It broke rods, and windowed the block in a few places beyond repair. A new 500 powerhead is around 25K, and the supercharger is around 12K if you go new. Unfortunately, mine spit parts through the supercharger base plate and into the rotors as well. The good news is that when you have one modified for upgraded internals, the block and crank are the only parts that stay stock. So if you have a good block, crank, and heads you can send it off.

Joe

Joe, I guess most of us won't go for upgraded internals until we have a see-through block and have proven that the stock rods and pistons weren't strong enough. My empirical experience assigns an approximate 50% probability that the crank will also be damaged at that point.

But for the wise folks, upgrading the internals before they break is certainly attractive.

Compared to the price of a 300XS powerhead and the price out the IMI factory gate of a supercharger, 25K and 12K aren't too bad, btw.

Do you have a idea what power you were pushing at that point?

My guess is in the 750 hp range and then we threw a 70 hp shot of N20 at them. We had fuel pumps that were rated at 700 hp and we were still lean on the fuel tables without the additional fuel required for N20. We went to 1000 hp pumps to bring the AFR back in line. This is also something that needs to be addressed when you turn the MoTecs up. The stock 4.6/450 fuel supply module will not support the fuel feed required. The 500 has an upgraded module that will potentially cover up to 650 hp, but my personal experience indicated a change was required.

Joe

Doesn't surprise me that the fuel supply doesn't keep up. You are pass the 125% design rule of thumb. Cool that that amount of power is available out of 4.6L.

He!! that means 600 could be a pretty reliable package.

Are there any stroker kits out yet? I wonder if the KONG 1000's are stock size.

There will be guys go going well beyond what I ever intend to. I want to use my boat on a daily basis with pump fuel. There are turbo motors on E85 being built that should be in the 1200 hp range. Outboard performance is just getting started.

Joe