If you don't know how to check the fuel pressure, don't bother. Have someone check it next time during service.
The next thing I was going to mention is - throttle cable....has it been touched recently?? Without guardian codes (beeping and limiting RPM), it can really only be lack of full throttle extension from the cable. My bet is it came loose.
Disregard the timing, you can't check that without being hooked up to a laptop. No distributor whatsoever.
May want to check the water pressure sensor. On the HO there is a little T that checks that verifies water pressure on the intake. Mine has developed calcium and the boat felt like it wanted to come off plane and not go any faster. Once cleaned all was good.
I know the software varied a bit through the years ('01-'11) and have heard a couple of stores about the IAC going bad without any beeps or logging a code in certain years. This put the 'puter in soft guardian mode. A friend had this happen recently in a 2003 model boat....chased the problem for over a month.
Hate to even suggest just throwing parts at it, but if nothing else take the IAC to your local NAPA or VatoZone and cross reference the part number. Mercruiser sells them for about $100, but it's a Ford part and NAPA has them for about $60 (last time I checked). Once you install it you'll need to have the 'puter reset to take it out of guardian.
.....if that's even it. Hopefully you'll find something simple before then.
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