2000 225 EFI mercury OT61607 possible electric

[rsundancer]

Couple of months ago the new batteries in Jan. were found completely drained when I got the boat out of storage. So I just assumed I left something on and I replaced them. Now this is has become a problem I can't isolate the issue. I also found the 20 amp fuse blown and replaced and so far it's not happened again but there is still a battery draining issue going on. Also the engine start right up but when you push the throttle up it goes to plane but seem something won't let the engine smooth out. Any ideas where to start looking?

 

[Faztbullet]

Check the alternator as these are know for problems relating to battery drain when not in use, these are welded together and non repairable.