i have a 500 efi in my 1998 272 spinning a 25 mirage + that has a mercury lab can only spin it 5100 and runs 70.9 it blows out just before it drops on to plane but if you ease in to it it is fine oh and my drive height is raised a couple of inches over stock i know mine has a little left in as the computer is good to 5600 but i am pretty happy with it for now until i get bored and whipple it LOL

4750 RPM sounds like you're down on power to me. You should be closer to 5000. The M+ 23 is the right prop for your boat HOWEVER it needs WORK. They have high slip numbers stock and blow out easy. With the diameter reduced, pitch increased, blades thinned and cup/rake adjusted for the Baja to carry the bow, you can pick up substantial "top end" without giving up anyhting else. My +/- 450HP with Bblades custom wheel (based on the M+23) runs very high 60's.

Well, she could probably use a tuneup too. Who knows how accurate the tach is also. What's one of those tuned props worth, roughly?

Would a 21 plus be better for him rather than all the work on the 23? I'm sure if he is looking every last bit out of it the 23 would be better but I would think that a 21 plus could be thrown on and be done. On the other hand though, it might be a wash?

Not to hijack, but since we are on the subject...I am getting a 496HO for my 272 and on hand I have a 21 plus and a 24 bravo 1...I would like to use one if I could rather than buy another or lab. Would one be ok? I know the 21 is too small and the 24 is too big, but would the 24 be ok or will it be lugging the motor too much?

True. Don't forget The ICM in the distributer cap while you're at it. I can't quote prices of coarse but mine was done at the shop in WI, (there's an awesome recipe in my file) less than 500 to have it tuned, balanced and blue printed I believe, but you'd have to talk to him to be sure. A lot depends on what you're starting with too.

A 21 wouldn't yield any top end gain for sure. I understood "top end" was the stated goal.

The 24 is prolly perfect for a stock wheel. Bolt it up and nail it.