Got a 2007 profile 260v been fighting for two months.
When you start it and it comes back down to idle it acts like some one turns key off and back on. It drops Rpms and then right back up with one beep. Also lost about 500 Rpms while running down water.

Changed plugs
Wires
Coil packs
Ignition switch
Crank sensor
Relays
Battery
Fuel pump housing and assembly
Map sensor
Impeller
Checked fuel pressure.

Any other ideas before I give up on the boat and let it set

What engine ?

Yes, what engine and you need to scan it instead of guessing. Your idle issue could be an IAC valve. Again, need to scan for codes.

If its carbureted has it been rebuilt? If not most likely it has the effects of ethanol fuel on it.

Sorry I thought I put the engine. It's a 496 ho mag.
It's efi. I have scanned it and it's not showing any codes and everything seems to check out. Only thing I noticed that seemed a little off was when I tried to step the iac with my rinda deacom software, it seemed to not affect my engine. I went from one extreme to the other and the idle never changed.

Thank you for the replies. I have been fighting this for a year now. Sucks being so frustrated with your boat that you don't even look forward to spring.