For two long years my 189trx with a 150 optimax has been .... well, lacking the performance that I expected with it. Full tourney load would yield a pathetic 49 mph at 5200 rpms. My dealer has been great (shout-out to Anglers Outpost and Marine) in doing everything they possibly could during this time to help but nothing seemed to work. Everything I've read said this should be a 56 mph boat and I would only gain 1-2 maybe 4 mph tops with a jackplate so even with that I'd still be short of my expectations.
I was contemplating selling the boat and buying something different. Heck, if I'm only gonna get 50mph outta this thing then I may as well just save some money and get the 175 with a 115. I thought before I did I'd better get a plate just so I'd know for sure. So, I got a manual plate and went out to set it. I started at about 3" below pad and was loosing water pressure, 1/4" down and was still at about 10psi on pad, down another 1/4" and BINGO 16-17 psi on pad 5500 rpms 58 mph with 1 person and a full tourney load, 56mph with 2 people. Yes, you read that correctly 300 rpm and 9 mph increase.