FWIW, back inna day (late 80's) I towed an 18' Bayliner (350 Penta outdrive) almost weekly, from 2000' elevation on the Big Island to Keauhou bay...it was only about a 5-6 mile trip (so yeah, kinda steep in places) but was managed OK with an 88 Toyota 4wd X-tra cab PU. (3L V-6, manual 5 sp)
I won't say it wasn't exciting the first few times, (very steep learning curve) but after I became aware of how slow I had to go on the way down, it wasn't too bad.
In hindsight, trailer brakes prolly woulda been a good idea...![]()