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wshott
05-20-2007, 12:51 PM
I own a 2003 Prostar 197 with an MCX engine and 1:1 transmission. I now live at 6,000 foot elevation and the boat feels like a slug out of the hole. It's maximum performance is 35 mph at 4,000 RPM.

I am guessing I need to change my prop. What is the right prop for my situation?

Is there anything else I can do beyond a new prop? Will gas matter? Are there changes that can be made to the multiport fuel injection?

03 35th Anniversary
05-20-2007, 01:31 PM
I own a 2003 Prostar 197 with an MCX engine and 1:1 transmission. I now live at 6,000 foot elevation and the boat feels like a slug out of the hole. It's maximum performance is 35 mph at 4,000 RPM.

I am guessing I need to change my prop. What is the right prop for my situation?

Is there anything else I can do beyond a new prop? Will gas matter? Are there changes that can be made to the multiport fuel injection?


I would think if your boat ran fine and had a good hole shot before you got to that elevation, that the prop is not the probelm. It sound more like your air/fuel mixture needs to be tuned alittle and probably a hotter firing sparkplug. Before I really changed anything I would check the plugs and make sure they don't have carbon build up on them. I have had this probelm a couple of times.

Storm861triple
05-20-2007, 09:10 PM
I would think if your boat ran fine and had a good hole shot before you got to that elevation, that the prop is not the probelm.
That is dead wrong. A given propeller works w/a given combo because that propeller is the correct "gearing" for that combo's weight, hull design, engine tq, hp, and RPM range.

When you go up in elevation, you loose tq (and therefore hp too) because the air is less dense. If everything is optimized at the 'new' elevation (timing, fuel ratio) then even with that optimization, you'll still loose 3% of your tq and hp for every 1000' gain in elevation. So at 6k, you're loosing 18%, or ~55 hp (I'm assuming a "300 hp engine"). Since you've lost 18% of your torque, or twisting force going to the propeller, how in the world can you expect the engine to achieve it's rated operating RPM?? It's doens't have enough "muscle" (torque) do so. This is hurting your situation worse than the 18% loss alone, because since the engine isn't achieving it's peak hp RPM, it's never going to realixe the max hp that it could make at that elevation; about 245hp. Instead, peaking at 4000 as you described, it will only be making about 200 hp. That's a recipe for a real DOG! -exactly what you're experiencing.

You need to get a different propeller with less pitch. Probably about 1" less. This will give the engine a little "lower gearing" and more mechanical advantage. It will achieve it's desired max RPM, giving you a higher top speed (than what you're seeing now), and give you a major improvement in low end accelleration.

You'll never see the type of performance that you saw at sea level, unless you modify the engine to produce the same amount of power at 6k, as it did at sea level. That means that you would need to build the engine to produce around 370hp, to make ~300 for you. That would be a bit of a tall order.

Lasty, your engine is fitted w/a "Baro sensor" that measures the air density. It compensates for changes in barometric pressure, or air density. This means that when you change elevation, the computer can "see" this and make the necessary fuel and timing changes. Now the fact is, the changes made at 6000' probably aren't perfect, (because the OEM probably didn't invest the time to tune specifically for that condition) but it'll be darn close, and WAY better than anything w/a carburetor.

In short, you need a prop. If that doesn't satisfy you, then you'll need a cam, and the requisite tunning after a cam install.

03 35th Anniversary
05-20-2007, 09:20 PM
Thats good to know. Thats why I got on here was to learn stuff like that.

Storm861triple
05-20-2007, 09:31 PM
Kew. :)

Is your boat REALLY supercharged?? What kind of charger is it? Who installed it?

A charger would REALLY help at these elevations!

03 35th Anniversary
05-20-2007, 09:37 PM
Kew. :)

Is your boat REALLY supercharged?? What kind of charger is it? Who installed it?

A charger would REALLY help at these elevations!

Yes, it is!

The brand is a whipple. Texas MasterCraft installed it.

I can't figure out how to put pics. into a thread yet. But there is a pic. in my gallery.

03 35th Anniversary
05-20-2007, 09:45 PM
Finally got it!!!

http://www.tmcowners.com/photopost/data/500/medium/Copy_of_IM000354.JPG

Storm861triple
05-20-2007, 10:10 PM
Damn....that's FBA. I dig it! I want one.

Tommy likey! :) :)

Do those exhaust manifolds say "Mastercraft" on them? Where did they come from?

That think must come out of the hole like a scalded cat. A raped ape. A..well, you get the point! What motor is that based on? It looks kind of like an LS1, but the pic is just fuzzy enough that I can't quite make out the valve cover to tell. :/

wshott one of those would "fix" your issues too! :D

03 35th Anniversary
05-20-2007, 10:19 PM
Damn....that's FBA. I dig it! I want one.

Tommy likey! :) :)

Do those exhaust manifolds say "Mastercraft" on them? Where did they come from?

That think must come out of the hole like a scalded cat. A raped ape. A..well, you get the point! What motor is that based on? It looks kind of like an LS1, but the pic is just fuzzy enough that I can't quite make out the valve cover to tell. :/

wshott one of those would "fix" your issues too! :D

The exhaust manifolds do say MasterCraft. They are part of the 35th anniversary package.

The engine is an LQ9 385 hp. 6.0 liter before the S/C now it runs around 520hp and YES, it comes outta the hole like a Top Fuel Dragster. :headbang:

Storm861triple
05-20-2007, 10:22 PM
it runs around 520hp and YES, it comes outta the hole like a Top Fuel Dragster. :headbang:
Oh MAN.....I so jealous! That, my friend, is a sweet package. Sweet.

03 35th Anniversary
05-20-2007, 10:25 PM
Oh MAN.....I so jealous! That, my friend, is a sweet package. Sweet.

One of my best friends has the same setup in an 03 proteam boat, and he jumps me outta the hole by 2 boat lenghts. But I can out run him on top.

Storm861triple
05-20-2007, 10:32 PM
must be they way you guys are propped.

What IS your top speed, BTW? I can't imagine getting one of those hulls over 60...even WITH that badassed power.

03 35th Anniversary
05-20-2007, 10:39 PM
must be they way you guys are propped.

What IS your top speed, BTW? I can't imagine getting one of those hulls over 60...even WITH that badassed power.


My top speed is about 54.8 got that the other day. The guy that supercharged it. Proped it to up 60 one time and to told me that it was all he could do to hold it straight and slow it back down. He said it was scary fast.

Storm861triple
05-20-2007, 10:45 PM
My top speed is about 54.8 got that the other day. The guy that supercharged it. Proped it to up 60 one time...
Wow. I can't believe it. I believe it really but, wow.


...and told me that it was all he could do to hold it straight and slow it back down. He said it was scary fast.
I'll bet it was "scary fast". I bet that hull feels like garbage at that speed! Crazy. I bet it feels awesome though, when you hit the gas from a stop, and it feels like you got rear-ended by a Semi! :D :D

I have to get off the computer now, but it was nice hearing about your sick boat. Like I said; I dig it. Later!

-Tom

DrJ
06-19-2007, 05:03 PM
Hey WSHOTT, I don't know if this helps you in any way but I have a 2004 X2 with the 350. The lake I am on is about 5500 feet and when I got the boat it still had the factory OJ prop on it. I contacted Acme and talked to one of the engineers over there. They were very helpful in figuring out what prop would be best on my boat. I ended up with a 4 blade 13.5 x 17.5 cupped prop. The hole shot is great but you still don't have much top end. I am getting about 44mph at WOT. I am very happy with the prop. So my advice is to call Acme. Let us know what you figure out.

Goinbroke
06-19-2007, 05:59 PM
I've Got To Have That!

How Much, And What Is Your Top Speed?

x7drvr
07-23-2010, 03:11 PM
how much is a super charger?
how much faster did it make you 6L go?
and how much would it improve a 350 hp?

Storm861triple
07-29-2010, 01:56 PM
how much is a super charger?
how much faster did it make you 6L go?
and how much would it improve a 350 hp?

~$2000 to $10,000, depending. Generally, about $5k

Tops speed is seriously diminishing returns on a comp ski or wake board boat. 800 hp probably wouldn't get you past 65 mph.

Generally you can cound on 40-50% more power. A 350 horse engine would probably be good for ~450-475 hp on ~6-7 lbs. But again, lots of variables.