You will cruise with the OPTI at the WOT of the 75, and burn the same gas.
2015 Ranger RT188 DC; BassCat Storage Box; Mercury Optimax 115ProXS;
19" Spitfire X7; Vessel View Mobile; Minn Kota Ultrex 80; GForce Handle;
TM Eliminator; Helix 7 G2N SI Combo F/R; HydroWave KVD; BBT 4" Angled Bow Mount; Durasafe Locks for Electronics and Ultrex;
Twist Step Boarding Ladder; EZEE Step ES1; BAC RAC Rod Storage; Motor Mate Transom Saver
I have a 75 four stroke with a Simons tune on my Crestliner VT17. You should get better than 40mph out of your 188. I can run about 50mph on mine. I could use a bit of prop work and a jackplate, then she will really fry. Nice Ranger and enjoy.
2014 Ranger RT188
Mercury Fourstroke
Was running a Michigan Wheel Apollo XHS 19 pitch at about 6300 on my factory tach at a best of 48.6 mph. Just got a 20 pitch LazerII that I am gonna have cup added to to try to bring the rpms down a bit. Also looking for a 4" hydro jackplate. Then start the whole process over again.