Hi..I have a 94 merc 225 that i just put on my 18foot maxum. First time out tonite..it has good mid to upper rpm power, but outta the hole it stumbles and shakes and pulls like crap. Seems once the boat gets planed and around 3000rpm it really comes alive. ONCE tonite it did run clean from a dead take off and it pulled really well out of the hole. I bought this motor from Kentucky and i live in Alberta canada...does it need to be rejetted for altitude? Thx