Boat won't rev up. Engine stumbles when trying to accelerate

[ColdNorth]

First run of the year. Boat started but stumbles. Put in forward or reverse and engine will stumble, sometimes die. In neutral, it won't rev up. Maximum rpm is below 1000. However, if I pull the cable to the MAF, I can get it up to nearly 2000 rpm and hold, but if I try higher, it stumbles back below 500 rpm. It will die when I plug in my MAF again. With the MAF plugged in, it stumbles along at 200 - 300 rpm. No power at all if I put it in gear  / quits. Not much more with MAF plugged in.
I pulled a couple of plugs. Very clean. Plugs are old (more than 10 years) but look like new.
I am not sure I am getting sufficient fuel. Is there a way to check without a gauge?
Boat has run near flawless. Currently has 480 hours. 2000 epic x22. Ran perfect before I garaged it last fall. I have had it for more than 15 wonderful years.
Also, I have never changed my fuel filter... guilty.
I am about to go grab new plugs and filter but not confident that is my issue. I am feeling it is fuel related.
Any thoughts out there epic magicians? Of course the grand kids are lined up on the dock...

My apologies if there is a similar topic. I searched and did not find / recognize my answer.

[Capt Rick]

1. go to get mass air flow cleaner.
2. take a picture of the way the label is on MAF sensor
Remove and spray alot on the inside.
let it dry and install.
3. Install new spark plugs keeping the order of the plugs as you remove them.
4. Place vise crips on fule return line located on fuel pumps side goes back to tank.
5. Remove air instake with #10 socket. move throttle cable from idel to full does the metal Flap open and shut( engine off)
Do each step and test
Does it ideal above 1000 rpm if so does the light stay on?

[ColdNorth]

Thanks for those steps Capt. Before I saw your post, we ran to town and purchased some items. Here is what we did:
1. Replaced plugs. All plugs coming out were still white almost like new. Consistent in color. - No Change
2. Sprayed the MAF sensor for the first time ever. - No Change
3. Replaced the fuel filter. Old one had rust and we tapped it around a bit and dark bits fell out. - Problem solved. Runs perfect.

I was not so confident the fuel filter was the problem but it was. Guess the boat got a tune up out of the deal.

Thank you again.