All you have to do is talk to a pilot and he can explain density altitude for you. Even though havasu might only be at 600 ft. above sea level, the heat will act as if you are much higher above sea level than you actually are. Hot temps are the result of thin less dense air that will not allow your engine to make peak hp. It also has the same effect on the wing of an airplane as far as lift is concerned. Ten miles an hour sounds about right depending on the boat.

air density= less hp

hot air is less dense
altitude less dense

less air to compress affect torque

I just bought the boat in May it has a bravo 28 and in May it only turnned 3800rpm, reproped to a 24 and got to 4400rpm. I was just out this week it 110 with out trimm I was turnning about 4200rpm 2 persons and about 60gl of fuel. 496ho is supposed to run best @4800rpm.

Turn around and go down river

Seriously though, there is also less density in the fresh water so your boat will lose speed in the fresh water too so that is another factor along with the heat.

Jimbo

I have gone down to parker its not that much difference.

yup 900 ft, starts to get thinnnnnnn.

That's why we always do our speed runs on the weekend of the Christmas Parade of Lights. Havasu I believe is also at 540 feet normal pool level. It also sounds like you need to get/test another prop.

I have bought a 24 bravo one, I'm still 400rpm short so I have to borrow a 22 bravo one and see what happens. But it looks like I have to spend more $$$$$$$ to get to 70-80 mph. I'ts e deck boat so that shuold be plenty beacause 60mph is not going to cut it. As it is only one insurance co will insure this cat anyway because they are supposed to be fast might as well maket a bit faster.

10 MPH sounds like a lot. Early and late in the season I run in temps in the 50's, low humidity. Then July/Aug. temps are 90+, high humidity. Top speed difference is less than 5 MPH.

I have never seen more than about 2 or 3 mph difference in speed in 60 to 100 degree weather. I boat on Lake Norman, NC at 760FASL and run Ilmors. I actually can not tell the difference in heat. And we really have some high humidity.
I know that when I ran a blower motor I could really tell a difference.