F150 Will only run at half its usuall speed

[phallgtown]

Was hoping someone could help, I have a 2006 F150 that i have had since new, always runs great, However one week ago while fishing the motor would not run at full RPM. My boat will usually do 46mph, i went full throttle and noticed it would only do 32mph, by the end of the day that dropped to 26mph. I changed plugs and fuel filter and went out again. Ran better for a couple of short runs then wnet back to 26mph which eventually dropped to 15mph and seems rough.
In idle and fast idle motor is smooth abd sounds great had rpm is not an issue. Only when boat is under a load.
I have noticed in other forums that this could be the injectors, need cleaning? never done in 7 years.
But i did notice when the cowling was off and i ran the motor that when in gear the fuel in the filter would drop to the bottom of the filter section and the ball would get soft. Is it fuel delivery, injectors or both.
I may have to take it in for service to salvage the year any help to figure this out is appreciated.

[Bilge Rat]

Injectors are at the other end of your problem.
They don't work if they don't have fuel.

Start at the tank, tank pickup clear, anti siphon valve working, tank to big blue filter clear?

Try pulling the hose off the engine side of the primer bulb. Get a piece of clear hose to fit on the bulb and a bucket.
Point the bulb up and pump to see how freely fuel flows out. Does the bulb refill quick or is it slow?
This will tell if a restriction is between bulb and tank.
If fuel flows good check the line from bulb to filter on motor.

Have you replaced the fuel line recently? Ethanol gas is eating the insides of the lines. This is a common problem. Cut it open to see the condition.

If the motor is pulling the clear filter dry the restriction is between there and the fuel inside the tank.
Pickup, line, filter, bulb.

An air leak in the line can be a problem but if the bulb is going flat it is under suction.

One other thing to check is the tank vent blocked.

[phallgtown]

thanks

Just wanted to thank you for the feedback. I havn't time to work on the motor myself. Was hoping to have it ready for the week end. I brought it to a local shop. I am going to show your comments. Thanks again