They will slip coming on to plane with a 4 blade and a high XD. Most of my friends here with 502 Mags and 496 Mag HOs run 26" Bravo 4 blades. They do work better with a 1" spacer. It may also help to have some cup added to your propeller if the slip % is still high. Most of the aftermarket guys like Imco make spacers in varying heights. I would look at Teague's website. The guy we used to source a lot of stuff through is out of business, unfortunately.......
X dimension is the vertical distance from your input shaft to the bottom of the hull, or pad on our boats. To measure it, measure from the center of your trim sender housing on the side of the drive to the bottom of the pad. You'll need to use a straight edge on the pad, sticking out behind the transom. It is not measured along the transom angle. You'll probably measure 18" to 19"s.

Most of us like and use the Hydromotive P5-X.
For a 500EFI boat, a 25" or 26" pitch should be close. They have an exchange program to get you the size you need.
I think Brett at BBlades also carries these now.
You may be able to find one in the OSO prop section too.
I would call hydromotive and Brett. They should have a good database for our boats (as to prop model and pitch).
www.hydromotive.com

Thanks Steve for the reply, the prop I have now already has extra cup in it. I just went and measured my XD, It measures 19 inches center of trim pod to bottem pad. Is that a good running number for a heat? What will a 1 inch drive spacer do for my boat?? Go faster, not slip as much out of the hole, etc? If I get a drive spacer will I need to change my prop? Sorry for all the questions! Thanks Garret

No problem Garret, we are always happy to help our Nordic brothers. If you run well, you'll enjoy your boat more, and you'll make the rest of us look better too. 19"s is way high for your motor and setup. Mine is 19.25"s, now lowered to 18.25"s. The 1" spacer will improve everything you are currently experiencing. You'll have less slip coming on plane and in the midrange, you'll have better top end #s, and better lift. It could be worse. A lot of guys have to buy shorties which are expensive, and we only have to buy spacers, which are fairly inexpensive. Your prop may turn 100 or so less RPM, but the slip %s will go down too, improving your overall #s at any RPM.
Regards,
Steve

Thanks alout Steve one more question, is a 1 inch spacer what I need or should I go 1.5?

Thanks Steve. I hope to have the prop back that I sent out earlier this year and try it, I think the next step is going to be the spacer. The measurement I came up with is 19 1/8. I will give Brett a call and see what we can do. I hope to get it close to 75mph, gotta try to catch my brother's Warlock!
Kevin

@ 19 1/8"s, you definitely need the 1" spacer. We'll take the Warlock down.....

Good question. It's possible you may need to go a little deeper with the Mag motor.
I would call Imco and Nordic and see if either of them have done this. I haven't done this exact modification to your engine/hull combination, and it's not an exact science. If you plan to keep the 4 blade, and I would with the Mag, 1.5" may be better.
The issue is, would the extra propeller lockup of the 1.5" spacer offset the additional hydrodynamic drag created by the lower XD? Is your boat an MCOB or closed deck? The MCOBs seem to need a little more lift, so that may help you decide.
Steve

Has anyone tried a left hand prop on a heat? I know it makes a difference on 27-29 Fountains.

Fountain did run a few left hand set ups in the 90s. I have 2 friends with good running 29's, and they are both right hand drive boats. One has a 525/Whipple, the other is lightly modified 575.
I think Chris did run a left hand prop as a test. Can't remember the results. With a right hand driver station on our boats, it is going to ride low on the right with one person and a left hand propeller.