Cpt Ahab
Go to Port Alice.
Coal Harbour is an old whaling station and as Heavyc pointed out, it is a very low sloped launch. You will need to put in and out at high tide and even that will require you to have your back wheels of your truck in the water at a min. Plus they charge you to launch ($10) plus park and if they get you to park your trailer in one spot and truck in another, they will sometime charge you $10/ vehicle -trailer/day....depending on who is around. Plus there is reports of gas and diesel disappearing in vehicles left there.
Port Alice is free, lots of parking and they dredged out their launch this spring, so getting a big boat like yours in and out is no problem. But to be safe, I would make sure it is on a reasonably high tide. It is the same distance to run and even the same distance to either Coal harbour or PA. The only thing to worry about is the road to PA, it is hilly and twisty, which could be a problem with your big boat.
any other questions, let me know.
Cheers
SS