another prop question

[bobbo268]

16.5 ft premeire pontoon, 1996 40hp mercury (non-bigfoot i believe, no marking to indicate such) WOT is about 5050 with the prop below (10.5p). If my research is correct it should have a WOT of 5500, and from further research, i guess for every 1" I subtract from the prop, it will give me on average 150 to 200 gain in RPM. If everything is correct, at 150 per inch I would need a 7 or 8p prop, and at 200 per inch I would need an 8p, so do i just go with an 8p prop like the one in this link? Do i stick with 3 or go to 4 blade and do i need to choose a certain diameter, or do you just get what it comes with and doesn't matter? (I don't have the money for SS, so I need to stick with aluminum)....
8” Pitch Mercury Outboard Boat Propellers 40 HP 1977 & Newer 2-Stroke, Includes Model 402 - iboats

my current prop (not sure on boat weight, and usually only have 2 adults and one infant on board, and extras are minimal, trolling motor, extra battery, 2 medium anchors, and towels and life jackets and the normal stuff)

 

[steelespike]

Re: another prop question

What is your gps speed at 5050?
Pretty sure your rpm range is indeed 5000-5500.
Your blade edges seem really thick Like they are actually worn
From heavily silted water, weed beds or contact with sandy/mud bottoms.
5050 is acceptable for your typical load and it may be closer to 5500 lightly loaded.
I think a new 9" Solas Amita or Rubex should help performance and increase rpm a little.

 

[bobbo268]

Re: another prop question

It's a new to me used boat I aquired recently. forgot to gps it last time but will have to remember when I go Tue or Wed