You sure about that? The 500 efi's were 470 at the prop. When did Merc Racing stop rating them at the crank?

JeffC, I saw your boat at the Marriot and I love the paint! I have seen so many white Cafe's it was a very cool change of pace for that boat. Sorry you had motor trouble. Good luck with your engine rework.


DK

I was lucky. It had the 2" shorties on, but with 2" spacers installed, so I got to drive the boat with both X's.

I feel I did pick up a couple MPH on the top end, and the boat seems to take a better set above 75MPH.

The only downside was quite a bit of blowout getting out of the hole, but if I want the drives to live, I really don't want them hooking up hard out of the hole, anyway.

Thanks for the info. I've been thinking about shorties and didn't know what to expect!!

I actually just read that on one of the insurance threads here. Ihave never seen dyno sheets on one.

I know the hp500 was 470hp though. You are correct on that.

I also read about the prop rating hp on the 525 from a tech on the tech forum. Don't remember where though.

I thought that the most you could get was a 540 or 550 out of a 502 block!

A 5.25 inch crank gets you a 540 with a 4.50 inch bore. Standard 502 is 4" crank with a 4.5" bore. A 4.25 inch crank with a 4.60 bore gets you a 565.

A 4.375 or 4 3/8 crank gets you a 572. if you bore it to 4.60 you get a 582". I have a couple of them in my shop right now.
I have one going out in a couple of weeks.

If you use a standard bow tie block or a later model gen V or Vi it requires the machine shop to grind out some extra clearance for the crankshaft so it can rotate. The 2 I built out of Dart blocks required crank clearancing also.

When I was at Mercury racing they were dynoing a few 525's, the pull I saw made 543hp. The dyno operator said they make a consitent 540 plus hp. I think at some point they started to under rate the power on all the "blue" motors.

Id go with making them 540s.Our 650 engine package is a Injected 540 with AFR heads. Very Reliable and tourqey,perfect for your bat.

Does a boat go faster in salt water or fresh?