can havasu heat kill speed ?
 

:mad: Has anyone experinced speed loss due to the high heat at Lake Havasu ? I've been told that my boats loss of almost 10mph is due to the heat . I've had the motor looked at and it has no codes, it just does'nt sound possibe, is it.

Re: can havasu heat kill speed ?
 

That sounds about right! Heat kills horse power......

Re: can havasu heat kill speed ?
 

there has to be something that can be done to cool the air a chiller fo example.

Re: can havasu heat kill speed ?
 

That is why chillers are added....to make more HP

Re: can havasu heat kill speed ?
 

Heat and altitude are both bad for horsepower.

Re: can havasu heat kill speed ?
 

Havasu I was told it's about 600ft above see level, thats not to bad, 10mph is like loosing almost or 100hp thats alot.

Re: can havasu heat kill speed ?
 

What power do you have? I wish I could add 10MPH by adding only 100HP!!

Re: can havasu heat kill speed ?
 

It's a 496 ho, and you are absoluitly correct it has to be closer to 200hp to losse 10mph ,ant thats my point do you really loose that much.

Re: can havasu heat kill speed ?
 

600 feet may not sound like much, but the pressure loss is 0.32 psi, or about 2.2%. That may amount to 10 - 15 horsepower.

Add 100+ deg temps, and it gets worse.

Also, without a prop change you now might be well outside of your horsepower peak, which further exacerbates the situation.

I can't tell you exactly how much horsepower your losing, but somewhere in the neighborhood of 50 sounds about right.

By your avatar, it looks like your running a cat......So, not only are you losing horsepower, but the higher temperatures and altitude also drastically reduce the lift produced by your tunnel due to the reduction in pressure, so you're fighting more drag.

It all adds up.

Re: can havasu heat kill speed ?
 

How Many Rpm Are You Turning
How Many Before The Heat.
What Is The Rpm Range For Peak Hp On A 496.
Loosing 350 Rpm Is Normal In Extreme Heat.

Re: can havasu heat kill speed ?
 

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.

Re: can havasu heat kill speed ?
 

air density= less hp

hot air is less dense
altitude less dense

less air to compress affect torque

Re: can havasu heat kill speed ?
 

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.

Re: can havasu heat kill speed ?
 

Turn around and go down river :eek: :D

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 :cool:

Re: can havasu heat kill speed ?
 

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

Re: can havasu heat kill speed ?
 

yup 900 ft, starts to get thinnnnnnn.

Re: can havasu heat kill speed ?
 

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.

Re: can havasu heat kill speed ?
 

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.

Re: can havasu heat kill speed ?
 

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.

Re: can havasu heat kill speed ?
 

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.

Re: can havasu heat kill speed ?
 

It's a "dry heat" folks......no humidity! :D

Re: can havasu heat kill speed ?
 

What about your x-dimension? Maybe the lower unit is too far in the water?

Re: can havasu heat kill speed ?
 

:D Nort, I've used that line a time or two myself. We're looking for 115 degrees tomorrow :eek:

MELTDOWN :evilb: :evilb: :evilb:

Re: can havasu heat kill speed ?
 

I flew out there about 3 weeks ago to pick up my repaired stuff from the Ford dealer and Absolute Speed and Marine (from the poker run).....116 degrees that day and it took me almost 11 hours to get home after a trailer tire blow out on the 40, dead battery from sitting with the AC's and lights on in 116 heat for 2 hours......it was friggin HOT. :D :D :D :drink: :drink:

Re: can havasu heat kill speed ?
 

High Heat and humidity = +Desity altutude = Power loss.
Airplanes are the same way. On a hot muggy day you will see parts of a runway you didnt even know where paved.

The easiest way to get the 10 MPH back is to do what the rest of us do when its hot. Tkae your shirt off, place it over the speedometer while your running, then lie about how fast you went.

Re: can havasu heat kill speed ?
 

2 hours to change a tire? I know it was hot, but come on Norty! You have all the toys, but no impact wrench? I changed out a center axle flat tire on the side of I-95 in 12 minutes flat AND I was wearing a business suit! (Took of the jacket of course.) I was on my way to a business appointment, and was taking the boat in for some work afterwards.

Re: can havasu heat kill speed ?
 

If my memory serves me right I was told it was 16''

Re: can havasu heat kill speed ?
 

Norty, when are you going out again?

Re: can havasu heat kill speed ?
 

Havasu about 450' elevation. It doesn't help when its in the 120's either...

Re: can havasu heat kill speed ?
 

10 mph loss is high in my opinion. Heat will hurt some HP but not that much. I run a 502 mag mpi with a few upgrades and ran it a couple weeks ago in 115 heat there in havasu. Not much difference when it was 90 early in the day then 115 in the afternoon. I was actually surprised as I expected more loss. I do not like to run it too hard too long in that heat though. I think it is harder on me than the motor. :D
Bigger HP motors will see more loss. Just my expierence.

Re: can havasu heat kill speed ?
 

Good rule of thumb, but its also affected by humidity. About 1.5% loss of power for every 10 degree increase above 70 degrees F. So 40 degree increase equates to about a 6% loss of power or in a 496HO case about 26HP, not enough to srub off more than about 2 mph at WOT. I can tell you from expierence that a problem that is also appearing on a lot of new boats is not enough air intake into the engine compartments at WOT. Remember a 496HO uses about 700cfm at WOT= 700 cubic feet per minute, or a block of air 10 foot by 10 foot by 7 feet every minute! Most new boats should have the engine compartment checked with a sensitive pressure guage to see if they are pulling a slight vacume at WOT. This is just like pulling back the throttle! Not enough air in not enough power out! Check your vent sizes and engine compartment air intake feed size. Remember although not as attactive as flat billet intake vents, scoop vents will inject more air at speed than the flat ones. Also on 496HO's you should prop for about 5000 rpms at Wot, this is where they produce the best prop speed versus max HP. As for most deck boats in the 25 -28 foot range there are very few that will hit 70MPH speeds with stock 496HO's especially in Havasu heat.
I know what the salesman who sells you the boat tells you your deckboat will do 70+ mph., but a little test drive with real loads in real conditions will make honest the real proof for the buyer!
Just some thoughts and info.

Ray @ Raylar

Re: can havasu heat kill speed ?
 

Just had this discussion on another board about making some kind of sealed intake system on my 502 mag(I don't want to cut up the sunpad!). Only two 16"x2" vents and my engine compartment seems to get very warm.

It actually got started because I was asking about running an intercooler on a NA engine to keep the intake temps low. Most agreed that the cooler air would be offset by the airflow restrictions of the intercooler on a NA engine so the converstion turned to allowing the engine to suck fresh outside OUTSIDE air.

It was 95* here and very humid this weekend. I lost about 200 rpm and 2-3 mph when compared to a 75* day with lower humidity.

Re: can havasu heat kill speed ?
 

Really? I'm at 1300 feet and I never really considered that I was losing that much hp compared sea level? :confused:

Re: can havasu heat kill speed ?
 

Pressure at 1300' is 14.06 psi, or a 4.4% drop in pressure from sea level.

Re: can havasu heat kill speed ?
 

Here's a neat calculator.
Start with 77 degrees, 29.235 inches mercury, 0% Rel Humidity, and 0 feet altitude, for a typical standard atmosphere at which engines are tested and rated per SAE J1349

Going to 600 feet, you can expect a 2.5% loss in horsepower, at 1300' expect a 5.4% loss in power. :eek:

At 600 feet and 110 degrees, expect a 5.9% loss.

Check it out:
http://www.csgnetwork.com/relhumhpcalc.html

I'm tellin' you guys, it makes a big difference. :cool:

Re: can havasu heat kill speed ?
 

Depends on the hull. My DCB's lost a considerable amount of speed from spring to summer in Havasu (about 8-10 mph). My Skater is not effected nearly as much.

Re: can havasu heat kill speed ?
 

Probably not this year...... :(

Re: can havasu heat kill speed ?
 

No....AAA baby! I was inside with the AC on watching a movie!
:D :D :drink: :drink: