Ok...I will bite.
Going to the prop you recommend what would I expect to happen to my performance? 42mph on a 9.5' beamed 25' boat aint bad. Would I pick up speed? Better fuel burn?
I don’t typically tell other people what they should do with their boats or what to buy, so all of the following would pertain to my 2520, which is 19 years old, has bottom paint, several anchors with a lot of chain & other gear that’s always on board before I load coolers & ice . Coolers for an offshore trip will be 2 x 165qts filled with ice and another couple of soft sides for food & drink.
On my boat that 18.5 pitch would have my Suzuki DF300APXX lugged big time and the engine would be slow to get the boat on plane and there wouldn’t be any chance that I could get the engine close to recommended WOT RPM with the boat loaded for a typical offshore trip. When operating in rolling seas, requiring changes in power to climb the boat out of a hole performance would be unnecessarily sluggish with the 18.5 propeller.
I would think that on the rare occasion when operating with under 1/2 a tank of fuel , just myself, running in calm water with the 18.5, the top speed would be faster then with the 17” but those are not realistic operating parameters for me.
I have an old 2001 Chevrolet SS Camaro with a 6 speed standard transmission, 5th gear is a do all gear on the highway. Car accelerates rapidly and if desired you can run well over a 100mph without worrying about the red line on the tach, 6th gear when you can use it will yield 100mph at 2200RPMs and 25mpg (not exaggerating). The car accelerates like a slug in 6th gear but when the road is open and you’ve got distance to cover it works.
Our outboards don’t provide the ability to change pitch so we’re faced with compromise and on MY boat running an 18.5 pitch would be like trying to drive my Camaro around in 6th gear all the time, whereas the 17 pitch is 5th gear and at least 80% of the time is the optimum gear/pitch.
If I had an 18.5 on MY boat, I’d replace it with a 17 and keep the 18.5 as an emergency spare. I also think my engine would thank me in the long run for not running around over propped which could shorten the operational life of the lower unit and or the powerhead….
