I am looking at a few boats that have dual 502 engines. Most have been 2017-18 model years, but a 2019 caught my eye and I find that Merc increased the hp from previous years. 2019 and up are rated for 430 hp, while the 2018 and previous seem to be rated at 380 hp. This is on a bigger Searay where they are 380 hp. I know that the 502 Horizon was rated a bit less than the 502 in smaller, sportier boats in the same year, but now I find that a 2019 Formula 350 is rated at 430 hp. Can somebody clarify for me what is going on with the different HP ratings ? And are their easy ways to boost the 380 hp versions a bit higher without resorting to supercharging or big-dollar rebuilds. Most of the engines have less than 200 hrs, so a huge amount of life left in them. Also, I see all of these boats are equipped with catalytic converters, and the cat cartridge itself is close to $3000- thats $12,000 for twins. Is there an easy way to bypass them if they go bad ?
Thanks in advance, and sorry for my absence for the last few years

From my recent research the 380 hp is the base model and the 430 is the HO high output model . They are basically the same engine except for the throttle body size and ECM tune . On the mechanical throttle body non HO versions they had a restrictor in the throttle body . On the electronic throttle body versions ( or DTS as mercury calls it ) the throttle body would only open a certain percentage for the non HO model. All that being said there is no place that can legally retune your ECM to make it the 430 hp HO model or remove the cats . Whipple did do ecm tunes years ago but not anymore . I have also read that the internals are not that great as far as modifying the engine / boost etc . Something to do with crankshaft being difficult to combo / balance with aftermarket pistons . It seems like an engine best left in stock form. Please anybody feel free to correct me if any of this info is wrong.

locked down computers can now be replaced with better more tunable options of coarse to enhance cats and decrease emissions....

Do these better more tunable options plug into the factory engine harness? Or like a complete stand alone system?

Could a person just change throttle body and find the correct ECM to turn it into a 430hp engine?

Or would it be easier to buy a complete aftermarket system and start from scratch?

I've been investigating this question for the last month or so . It seems like all the 430hp HO engines have Cats and DTS Electronic throttle body . I have yet to see a mechanical throttle body - non EC ( no cats) HO version . I think they did make it but I haven't seen one , which makes finding a used ECM tough.

The only reason I think a mechanical throttle body HO engine exists is because of this picture and info I found here on OSO .

You can return your PCM, you just can't Later emission settings on the 2011 up Carb Compliant engines, if you live in the West Coast. Slightly different tunes, it typically it's a shade more compression and a few more degrees of camshaft duration.

Your right. You can piggyback a Motec or Fuel tec.