Could a 4.6 tow a 5th wheel with a 500 hitch weight and over all weight of 2800 unloaded (a 20' lightweight 5th wheel trailer). And how can you tell what size engine is in a 2005 crew cab. I paid cash from a private owner, was told it was a 5.4 but I don't know how to check it to be sure.

 

4.6 should pull 2800lbs without a problem, but being it is a screw, the payload capacity isn't the greatest to start with and loaded with people and gear +500lb tongue weight might get close to the payload rating. It should say on the under side of the hood what motor you have, the intake/air box is different on the 5.4 too. The payload capacity should be listed on the drivers side door IIRC.

 

The first picture is the engine bay of the 4.6L
Second picture is the engine bay of the 5.4L

 

It's not a surefire way, but just check the F150 badge, it'll say 5.4 Triton, or just Triton if it's the 4.6

 

The top of the air filter box says "5.4L Triton" also...dead center of the 2nd pic I posted earlier.

 

I second that.

 

Isn't it on the door sticker? There's also a website (which I can't find right now) that you plug in the s/n of the truck and it will show the window sticker on it for truck around 5-7 years or newer.