Prop suggestions/opinions/help...

[Looseties]

I know this is a subject much discussion, but need some input/suggestions/opinions.
I have a 2010 South Bay 20' with a F-90hp Yamaha 4stk, 25" dia logs (2), 5200-5400 RPM WOT.
If memory serves, I believe my factory prop is a 13.25 x 13 - 4 blade aluminum (Solas). My motor is mounted on the second hole down and the cavitations plate is almost even with the bottom of the mounting. I've under skinned the boat. The current prop has plenty of torque and will make you sit if standing when you hit the throttle or be prepared to spill your drink. I am looking for less torque and more top end speed. I currently run in the mid 20's and think I can get more. Any suggestions on 3 v/s 4 blades and suggestions on size changes. I think the RPM range for this motor is 5200-6000 so I have some room to play. Your input/expertise would be most appreciated.
Thanks,
Looseties

[playcat]

A 3 blade might help, but what you are looking at gaining is only 2-3mph at WOT. Sure that is worth the price of a new prop or two?

[Looseties]

Agree, but need to pick up a spare prop anyway. I've always carried multiple props on all my boats; never know when you may need one or when a half submerged log decides to meet your boat.

[Shopguy]

Could try the same size in a 3 blade. That should put you in the upper end of your RPM. My boat is one pitch too high and I'm at the bottom of my RPM with a normal load. I'll buy another prop to compensate for that but I wouldn't expect a noticeable diff in speed. Maybe a couple, but nothing that would matter. Mainly because I'd only be gaining 3-400 RPM.
I wonder if you could get an idea of what's to be gained by doing a test...like.... running the R's up to say 4000, check GPS speed, and then bump up the R's to say 43-4400 and recheck speed. Would the results be the same on the top end of your RPM? That'd give you and idea anyway.
Judging by your RPM now, you'd need to pitch up if anything. That would still give you more bottom end and maybe a wee bit on top. Definitely don't need to go bigger in any direction.
Option two....Horsepower.

[gramps]

Try a 3 blade, you will get more speed. Most toons have a 3 blade on them, ours has a 4 blade and the dealer is installing a new 4 blade for us as the prop that is on it now doesn't perform that well.

e-bay has a lot of used props that may work for you and save you some cash.

[dockholiday]

Normally would not suggest this for a 90 but since you got a 20ft boat an assuming it is fairly light you might benefit from a ss.prop. You could contact prop gods in Fla and see what they have to say. Good reports from a lot of members that have used them.
doc

[Looseties]

Thanks for the input....I will probably pick up a 3 blade for a spare and see if I can borrow a few for experimentation.