1998 Merc. 225 efi losing power

[225pro]

In the water, my merc. 225 efi starts fine then idles rough after a few minutes. If you barely shift into gear, it tries to die. Give it a little more throttle, then it acts if it's gonna run ok. Getting on plane is alot slower than normal and WOT is slower than normal also. Then at the ramp, it barely will pull onto trailer.
Out of water with ear muffs, everything I mentioned above does not happen....It
runs great. Compression in all cyl. are right at 125, put new plugs, new fuel filter, added Star Tron Enzyme fuel treatment to new gas, also sprayed Berrymans B-12 carb/injector cleaner through fuel lines and nothing has seemed to help it out.....CAN ANYONE HELP ME OUT???

[boats.net]

Probably need to test fuel pressure, check synchronization and throttle position sensor checked.

[225pro]

Improving, but still a lil sick

I appreciate all the advise that has been given to me. Here is where I stand now. After I replaced all fuel lines & bulb and with both tanks bone dry, I added new gas (plus a man from a local marine dealer nearby told me to add a bottle of Quickleen engine treatment with the new gas) and after running it several times, it has slowly started to improve once on plane & WOT. But still having trouble while idle, getting on plane and loading on the trailer. For instance, when I back in the water, my merc fires right up on the 2nd turn of the key (like it always has) and sounds great. By the time I back off the trailer, pull truck/trailer out and walk back down to the boat...Well, in that short of time it sounds as if you were to idle the engine down as low as possible without it dying. But I havn't adjusted the idle. Then still slow getting on plane & every time I start it while I'm out, it will idle real low but doesn't die. Loading onto the trailer seems to be getting worse & worse.
As long as I've owned the boat, on avg. it'll usually run about 75 mph, but that is loaded down with all my tackle & other fishing gear and gas in both tanks.

When all this trouble started, it wouldn't even run 65 without all the fishing gear and with only about 1/4 tank of gas in each tank.

Now, this past weekend, I ran a 2nd bottle of Quickleen treatment thru it and was on the water 3 different times with 1/2 tank of gas in each & some fishing gear and now it's running almost 70 @ WOT.

So, basically my sick merc is starting to get better. If anyone has any suggestions to try to fix the other problems I mentioned, I really would appreciate it alot.