i have two 500 HP's and was wanting to build them to get more power and speed and wondering which way to go?

Call Bob Madara.

Blowers or heads/camshafts or whatever you want Bob can help.

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I'm interested in researching options for my hp500 as well.

What was your budget and goals?

Looks like new heads and cam can get you over 600 hp, heads $1600, cams are ? and then what else?

What would one expect in labor to put in a new top end?

I spoke with Eddie Young in Tn. YOUNG PERFORMANCE found him to be very easy to talk to and a mountain of information, I'm sure he could help with some options

Ron Potter can do a lot with these motors too.

What if you want to reuse the HP500 Steel heads, (running in salt water) and just have them ported and massaged.....

Bob Madera helped me with my HP500 build. Went with AFR heads, custom cam, Willies carburetor. Bob has perfected this combination. give him a call. He is a great guy to deal with.

I also agree call Bob M. The new AFR 290 ovals would make a killer head for your combo. I have a Marine Kinetics Cam, AFR 265 Ovals and a Pro Systems carb all from Bob and I'm making 525 hp out of 439 CI. The same combo in your boat would make around 600 hp.

Since this is the "boating on a budget, do it yourself" section, how much more HP are you looking for?

You could easily do a cam upgrade from your current 731 to the 741 or even the 651 for minimal $$$ investment, then some good heads (bigger investment) and you should be around 600 hp.

If you want to tear into the engines (even bigger investment) you could go up to 509 cubic inches and increase the compression to 9:5 to 1.