Offshoreonly.com - 500EFI question

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I’ve found many older threads asking similar questions about this but no definitive answers...
i have 1999 500EFIs still sealed (300 hrs.) next winter plan on freshening heads and new roller lifters... I know the
intake and TB are the limiting factors on these motors but would I gain any noticeable power going with better flowing heads ? or changing to 525 cam? Or wast of money for 20-30 hp.
I’m running 95-97 now but would be nice to be 101 🤔
Thanks.

Quote:

Originally Posted by lucky cat (Post 4692452)

You can gain with aluminum heads, Arizona Throttle Body, and Cam Change. Then in needs to be tuned. Also Fuel, Injectors. Even with the stock 502 if you kept the bottom end, you can still make an additional 75-100 HP with these upgrades. I would say 575HP-600HP. To do it correctly and actually make the HP, certainly takes some coin. If you go 540 on the bottom end, and upgrade everything including cleaning up the intake and having them through honed and polished, matched to the heads and throttle body. 668HP is the best I have seen, that is fully dressed and dyno'd. at 5500. At 5501 rpm, it falls flat on its face and the Intake limits....not enough air. This is also running 92 non ethanol fuel

By the way......If bottom end is strong, best bang for the buck is whipple the motors. Most cost effective. pretty close to same money. Maybe even cheaper

Thanks Cigrocket, great advice...but I didn't want to get crazy with the HP , just wanted Xtra 75hp or so to get me 3-4 mph since I'm doing heads anyways...I have a 1080HP procharged 540 from my last boat and second m-3 kit and bowtie block with SCXs waiting in the wings... but not wanting to put bigger power in this boat right now, I like the reliability of the EFIs for now.

Id leave it alone, some after market heads have raised exhaust ports which can cause alignment issues with your pipes going through the transom.