Prop Question

Hello fellows, I am new here but not new to boating and fishing...

I am replacing the prop on my 1983 16.5 foot Tracker with a Mariner 40 HP (Yamaha mfg.), it currently has a 10 3/8 x 14 pitch and I get 23.5 to 24 on a calm day WOT. A few years back it would easily do 27-29 and was not as revved up. Michigan Wheel Vortex recommend an 11 pitch but I am wary of taking too long to plane. I Was thinking 12 or 13 pitch, with a 10.5 diameter.

What do you folks suggest?

Is your floatation foam waterlogged? That could easily add hundreds of lbs to your rig, possibly account for the loss of speed. Just a thought.

If you did 27-29 with a 14 pitch before...it should do it now,unless the hull is damaged,waterlogged,prop dinged or motor is not up to par.etc
13-14 seems about right..do you know your rpms?

I ripped out the foam and replaced it...

I had a lower pitch prop back then, (the original one a Mercury OEM) but I do not remember what pitch it was.

I am sorry I am clueless about my RPM, but I think I want to install a RPM gauge.

I mean it may also be the age of the engine I use it about 4 times a week.

Is 23-25 about right for my boat? I weigh 200 lbs plus a dog, 12 cat rods, two box anchors, and a cooler of bait. When I add a second person it will go about 22 mph, but it sucks up gas.

What about going up to 10 x15? It is still within the specs, (I think)