1984 Mercury 90hp Tower of Power - Correct Prop / Performance?

I have a 1984 Merc 90hp on a 1984 Glastron SSV-151. I'm not sure if it is the original motor on the boat as I am the third owner.

Motor is running fine, but I cannot get the boat past 32-35 MPH @ WOT regardless of where I set the trim. Everyone who has seen the motor / boat on the water has acted a bit surprised when I told them the top speed. The motor is currently mounted using the second set of holes from the top of the bracket.

Prop is a quicklsilver prop with a 19" pitch. One guy called it a "power prop". It does have a decent hole shot. Any recommendations as to the prop pitch / motor mounting that will help with top speed?

Thanks!

Re: 1984 Mercury 90hp Tower of Power - Correct Prop / Performance?

My ex 115 Tower was mounted on a 19 footer. Had a tach on board and with a 19" pitch prop it would rev above 6200 rpm . Changed the prop for a 21" pitch and gained a lot of top speed with 5400 rpm at wot.

Re: 1984 Mercury 90hp Tower of Power - Correct Prop / Performance?

Here is the secret to propping a boat...you have to have a tach in order to know that you have the right prop on your boat..You cannot buy a prop off the shelf and expect it to work..Every boat is different in its design and how it works with a given motor. With that being said, get a tach and see what the 19 is taching at..You want to reach 5500 like Pechex reaches on his.. If you are past that you are over revving the motor and you need to pitch up...for every inch of pitch you increase or decrease, you increase or decrease the rpm's by 200...If you are under 5500 you are lugging the motor and will do damage to it...Like taking off from a standstill in 3rd gear with a standard shift car...you will know very quickly if you can step to a 21pitch or down to a 17 pitch...those will be your options but only when you can tell us what the rpm's are......