I've got a pair of 1995 502 stock motors with just shy of 700 hours on them. When I have them refreshed I want to make more power. What is a good ball park figure to getting them to 540's and keeping them naturally aspirated?

If they are the MPI motors you'll have to ditch all that and go carbs.....just no way to get enough air through the 502 plenum (I had the same problem when turning my 500EFI's into 540's)

Compared to a re-fresh you'll also need: Machine work will be more, crank/rods/pistons/cam. If your boring it then you'll need head "work" at minimum if not new heads. Then carb/intake/ignition if replacing an MPI system.

I would look at putting good heads on 502s, ahead of stock heads on top of 540s.

http://www.offshoreonly.com/classifi...o44392-en.html

http://www.offshoreonly.com/forums/n...our-502-a.html

Seems like easier way to get more power is good heads and a cam change, reflash, HP500 intake or modify existing, better exhaust.

2K for rotating assy
2K for cam, lifters, rockers, springs, pushrods
1K machine work
+ whatever amount you want to spend on heads
Add anouther 2K for oil cooler, lines,fluids, gaskets, accessories and dyno.

Should be able to do it for about 10K each

While I think your close on parts, the way I read his post he's paying someone to do the work.......Labor is going to be another 2K

Plus you might as well upgrade the exhaust or else you'll be all clogged up there so add $2000 for that and then you need to re-prop to get all that power to the water so add another $1000.

Hope your drive is in good condition.

Wow , nothing like discouraging a brother . Who sells the best balanced 540 rotating assembly for the best price . My 500 H.P. wants to be a 540 when it grows up !! Can you say RM Builder !! Don't mean to hijack .