I have a 135' run to my boat lift
For a temporary cord cap you are probably going to have to use an industrial grade cord cap. Leviton -  black &amp; white lists #10 AWG with cord sizes up to .700" (strain relief insert removed for the larger size). Part #'s 5269-C &amp; 5266-C. This is not an endorsement I just happen to have some on the shelf. Be prepared for a bit of sticker shock compared to non Specification / industrial grade cord caps. Hubble also makes one almost exactly the same. These are the 2 brands I normally use.