That is much stronger than I thought that package was, Perfect Storm, thanks for the info.

I wonder what the Ilmor boat will do when they dial it in. I was pretty shocked when it only ran 78. I believe those engines are a good bit lighter, and they are rated at 45 hp more each. It seems like that combo should be good for a solid 85

It ran 81 out of the box. I think your 85 number will be close after prop/gear ratio is finalized.

I don't recall seeing heat exchangers on the 500's. Are they fresh water cooled like the 525's? A major consideration if you are in salt. Didn't they go to aluminum heads on the 525's?

As far as I know, 500's are not fresh water cooled, and 525's are, also 525's have aluminum heads, 500's use iron heads.

525's are closed cooling and the 500's are not. Fewer valve spring issues with the aluminum headed 525. 2-4 mph difference. I think everyone nailed it down pretty good.

No x dimension changes, but boxes made a 1-3 mph difference.

Dave

Took the boat out for our "new to us" first run on Lake Erie, launched out of Black River in Lorain, OH on Sunday 5-19-13. Spent 2 hours just learning the boat and its layout. Drives like to be trimmed in on launch with tabs neutral, keep it at 3,000 rpm and wait for it to hook-up. Trim out drive and let it run! Did a couple of speed runs and 83mph with 2 people and 3/4 tank of fuel, great way to cap off a good day.

Just a suggestion, only tach it up to about 1500, then progress to 2000, then to 2500, and then to 3000 waiting 10-20 seconds in between changes. It lets the heavy boat "catch up" to the prop. It will also save you an expensive drive repair in the future!

Dave

I pulled some of my old power boat magazines out last night and in 2003 they tested 353 with 525s 33 labbed props 85 mph with Bob T at controls.

Older thread about 353 and speed :-)
I know for a fact that there is a 353 Fastech in Sweden with merc 600 tuned dynoed at 711 hp, doing
100 mph at the gps. The owner is sure that there are a couple of mph more in it :-)

I have a 2000 353 with 500's and it will run 80 moderately loaded - 4 people and 1/2 tank of fuel, bravos 30p not labbed, no boxes, 280 hrs on the boat, although I rarely run it flat out, the ocean often doesn't cooperate. Great engines, no problems other than a fuel pump relay. The CMI's seem to last longer than on the 525's. I replaced mine two years ago although I had no leaks on the originals. Also replaced the original valve springs which also had no problems. I always fresh water flush the engines myself after a run in the ocean. Met a marina owner (fresh water) who had the same boat as mine, a year newer with 600 hrs and he told me he had never done anything to his engines other than regular maintenance like changing oil and had zero problems with them. He had not replaced the valve springs. My boat does have the changed x dimension that formula instituted I think in 2000.