My experience has been that an automotive scissor or bottle jack is often not hefty enough for a boat or travel trailer. With a vehicle you're typically just lifting one corner. With a trailer you're lifting the whole side of the unit, ie. much more weight.
I carry one of these in my Yukon since I often tow a 28' travel trailer as well.
You just wedge it under the axle, pull forward a bit, and the jack rotates under the axle and lifts it up. I place a chunk of old carpet between the jack and the axle so it doesn't scratch the axle.
2005 X2, Viper Red, MCX, OJ TZ-X5 prop, PPass, rear 750 sacs, KBS, IBS, Bennett Wake Plate, custom wake shaper
(previous) 2001 X5, 1991 TriStar 190