I have a 2010 Z520 with a Mercury 250 Pro XS running with a 27p Fury. I got the motor serviced recently and everything checks out fine.

From a stand still in the water, I can only get on plane if I gas it to 3500 RPM...anything over 3500 will cause the prop to spin out, anything under that and the bow won't go over. It takes a good 5-8 seconds to get the bow over and to get on plane. When it finally does get on plane, the prop will spin out for a quick second, then settle in and run like a dream.

This has been happening for about a year now, but I always keep forgetting to ask you guys about it.

You're over propped and your motor may be a hair too high. Go with a 25p, especially in this heat.

your motor is to high and your prop is a hair big for the high humidity. start by measuring the bottom of your pad to the center of your propshaft. It should be near 3 and 1/2 inches. I am guessing you have a manual jack plate. I would try a 25 or a 26 tempest plus

This has been happening for about a year, and 6 months ago I had everything serviced and the prop hub changed, and it's still doing it. So I don't think that's what it is

My Atlas jackplate and trim are all the way down as far as they go. Could I still be too high if I have a hydraulic plate?

You can't turn a 27p on that rig in this heat. Go down to a 25p.

this will fix you

I think that's what I'm going to do. I didn't know heat/humidity had that kind of an impact on props. To be honest, I don't really understand props all that well!

Not so much the prop as it is the engine losing horsepower due to high heat and humidity. I have to downsize props in the summer too, many do.

just borrow one and try it. I am close to dallas and you can try mine anytime. I run a 25 tempest plus

http://www.anglerworld.com/bassfish/bassboard/boats_motors/message.html?message_id=217518

Read this Jkrez and outdoor dude is correct but I didn't want to get into that. At 85% or higher humidity, your motor will not atomize fuel/air mixture as efficiently and you lose horsepower making it harder for your engine to turn that 27p.

Can yall recommend the optimal prop?

I'm having the same issue with my Skeeter, running a 27M, I have lost all kinds of hole-shot and speed just in the last few weeks, about to drop down to a 25T-1 for summertime......good times are back!

I would contact Steve's prop shop in Quitman(call him) or he hangs in the lower sections of the forum...
Boats and Motors and General Equipment...
He'll prolly get you to try a 25 Fury.

Try this:
http://www.google.com/search?q=Steves+pr...p;client=safari

I have a lighter boat but went through the same issues. I went to a 25P Fury and it planes out much better in the warmer conditions.