What do you Think ?
 

I finally got to run my boat to make sure there where no problems before we haul it down to Havasu next week. Its a 2002 Lavey 29 Nu Era Closed bow 502 EFI it came with a Bravo 1 26 pitch that i was told did 73 mph at sea level. I just ran it yesterday at 4700 msl with a 24 pitch Bravo 1 and could only get 4400 rpm at 50 mph. So seems like for this elevation I could drop to a 22 pitch? My home reservoir is 7500 msl I'm guessing I will need to drop even further?

I'm not a big elevation expert, things here are at sealevel. But that seems like one heck of a drop. You are not even in the rev band now. If the elevation is affecting it that much now, the 22 would be the prop for 4700. Next would be something like a Rev 4 17" or 19" for the 7200 elevation. It seems way off to me. Maybe you should post this in the tech section as well. Could there be another engine related issue perhaps?

Anyway, 73 seems kinda steep. I know a Fountain 27 runs about 71-72 with a 496HO and the 29 is a mid to high 70's with a 500EFI. Those are pretty efficient hulls.
I could be wrong, just thinking.

Go to the Lavey section and shoot Lavey jr. a pm too.

Thanks for the input, I will post in the Lavey section. Engine sounds great and seams strong. Idles nice at 750 crisp response on the throttle.

You are going to run out of prop. If you run at those levels a lot you might think about trying a 1.65 ratio gear set. That would let you be able to use the carrying power of the bigger props. Just because you get your rpm up doesn't mean your speed will be there. You run out of blade area on those smaller props.

GAZ, as a "general rule" you will drop about 5% in horsepower per 1000 feet of elevation. At the elevations you mentioned you are down 25-35% of your sea level horsepower. I go to the Tetons and Jackson Hole each summer. At these elevations, 6000+ feet, even our Corvette feels the effects! You see mostly turbo diesels in that neck-of-the-woods as the turbos are so much more efficient. A.O., along with a few supporting vendors give excellent prop advice. If a supercharger is in your budget it might be something to consider if you ever want to see sea level speeds at 7000'. You could change pulleys depending on your location. I am not familiar with your brand of boat so I cannot comment with any knowledge about the possibility of its top speed.

My 22 footer at sea level with 22 degree deadrise and 4200 lb dry displacemnet doesn't go that fast with it's carbed and tweeked 502. I'm spinning a 24" prop @ 5K rpms. I can't image yours would get near 70 with practicaly the same engine.

That depends on the efficiency of the hull. Plenty of boats above 24' can reach the 70 mark with a 502MPI, Also non stepped boats with 24* deadrise like the 23, 24 and 25 Bajas and several others, not to mention 21-22* deadrise boats like the 230 Stingray, and plenty of stepped hulls up to 29'. The Lavey hull is a pretty good hull, so not that far fetched. It's definetly a 65-70 nph boat.
Which 24" prop do you spin and what is your top speed? Sorry about the hijack, just a bit interesting.

It's a Bravo I 4-blade prop that was labbed a number of years ago. there are a few dings so it could use some work. I've seen 72 on the speedo but more often it's a bit less than that.

I'm aware of the horsepower loss with altitude, I use the exact figure you stated.

Do Not want to supercharge! Have a supercharged Mustang LOVE IT! But not for a boat to much hassle with fuel.

I do not want sea level speeds. Just want to go as fast as the boat can at this elevation naturally aspirated with the right prop.....

But, and this may sound crazy I want a good hole shot for skiing/tubing. The other day with the 24p at 4700 msl it did get on plane quickly and would stay there clear down to 19 mph! with a great wake for skiing or tubing!

I know I'm asking for alot but I was real pleased with what it did the other day. Just wondering if running a prop that will not let the engine spin up to the higher rpm will be harmful.