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View Full Version : Making your mastercraft faster?


EarlyriserX9
07-16-2012, 02:53 PM
I've had my 03' X9 with Predator 5.7L 310 for a few years now. I am still using the standard OJ prop that came on the boat when it was new. With the stock configuration I top out around 44mph. I was wondering if anyone has had success with changing out props or doing other modifications to make their MC's go faster? Right now I cruise at 2500-3000 RPMs which runs me between 22-27 MPH. I'm not complaining... its a towboat... but if I can switch props and get better performance without straining my tranny and engine, I'd like to.:rolleyes:

madcityskier
07-16-2012, 08:46 PM
There have been previous threads on this. How much are you trying to gain? Some prop change can help, at the cost of low end pulling power (generally). Some engine mods can help. The gains are usually subtle.

trickskier
07-16-2012, 09:46 PM
The second number on your prop - 14.25 X 17.5 is the pitch. The pitch means for each revolution of the prop the boat moves forward that many inches. So in the above example the boat would move forward 17.5 inches per revolution. If you want to go faster get a higher pitch prop.

TRBenj
07-17-2012, 09:42 AM
If you want to go faster get a higher pitch prop.
That is not how it works for direct drive inboards. Increases in pitch can just as easily slow the boat down. The trick to maximizing top end speed is getting your WOT RPM's to approximately match the point where your engine makes its peak hp. Generally speaking, direct drives that are propped for all around use (generally the case from the factory) are set up this way from the get go. Changing brands of props (Acmes tend to run a touch faster than OJ's in my experience) and going to a 3-blade from a 4-blade (if available in the proper size) can sometimes add 1-2mph. But youre not going to make huge changes to the top end unless the boat is propped entirely incorrectly right now.

To make a significant difference (3-5mph) then youre going to have to start thinking about adding horsepower, and usually quite a bit of it. Inboard ski boats have a lot of wetted surface to overcome, so youre usually talking about adding 20hp or so for every 1mph you gain.

willyt
07-17-2012, 09:51 AM
you want to go faster than 44? must be some big barefooter dudes.

sure you dont want to make it louder too?

TRBenj
07-17-2012, 01:13 PM
you want to go faster than 44? must be some big barefooter dudes.

sure you dont want to make it louder too?
44mph unloaded is probably closer to 41mph with a footer behind it. At 195lbs, thats too slow for me for 1 foot tricks. I dont understand why this question is always received in a negative light on this site. Someone needing (or heck, just wanting) a few more mph out of his boat seems plenty normal to me!

Nothing wrong with loud pipes either. The Sportster, Sportstar and 197TT are the loudest "new" boats on my lake... though nothing quite matches the tone of the vintage Correct Crafts. I am biased, of course.

thatsmrmastercraft
07-17-2012, 02:07 PM
44mph unloaded is probably closer to 41mph with a footer behind it. At 195lbs, thats too slow for me for 1 foot tricks. I dont understand why this question is always received in a negative light on this site. Someone needing (or heck, just wanting) a few more mph out of his boat seems plenty normal to me!

Nothing wrong with loud pipes either. The Sportster, Sportstar and 197TT are the loudest "new" boats on my lake... though nothing quite matches the tone of the vintage Correct Crafts. I am biased, of course.

I think willyt was facetiously referring to a short term member here who got a MC when he should have gotten something else.

scott023
07-17-2012, 02:13 PM
I think willyt was facetiously referring to a short term member here who got a MC when he should have gotten something else.

I was thinking of the same guy. lol

TRBenj
07-17-2012, 02:20 PM
I think willyt was facetiously referring to a short term member here who got a MC when he should have gotten something else.
I realize that. While its clear that tournament inboards are not go-fast boats, I still dont understand why anyone would scoff at making them a little faster and a little louder. The case can certainly be made that the improved performance makes them that much more functional as towboats. Especially if youre loading the boat down with weight, pulling big barefooters, multiple barefooters, etc. Or maybe you just want to be able to be the first boat back to the dock- whatever. Ive been in several inboard ski boats that run into the 50's and not only are they extremely competent ski machines (moreso than a stock boat), theyre also an absolute hoot to ride in and drive. Whats not to like?

thatsmrmastercraft
07-17-2012, 02:29 PM
I realize that. While its clear that tournament inboards are not go-fast boats, I still dont understand why anyone would scoff at making them a little faster and a little louder. The case can certainly be made that the improved performance makes them that much more functional as towboats. Especially if youre loading the boat down with weight, pulling big barefooters, multiple barefooters, etc. Or maybe you just want to be able to be the first boat back to the dock- whatever. Ive been in several inboard ski boats that run into the 50's and not only are they extremely competent ski machines (moreso than a stock boat), theyre also an absolute hoot to ride in and drive. Whats not to like?

No argument here. My '77 could use more hp and I will at some point be building an engine as a winter project, along with rebuilding the trans. Mine has a beautiful sound, but many newer boats are awful quiet. It could be worse..........we could have single exhaust. :rolleyes:

EJ OJPROP
07-17-2012, 05:32 PM
I've had my 03' X9 with Predator 5.7L 310 for a few years now. I am still using the standard OJ prop that came on the boat when it was new. With the stock configuration I top out around 44mph. I was wondering if anyone has had success with changing out props or doing other modifications to make their MC's go faster? Right now I cruise at 2500-3000 RPMs which runs me between 22-27 MPH. I'm not complaining... its a towboat... but if I can switch props and get better performance without straining my tranny and engine, I'd like to.:rolleyes:

What is the max RPM at 44 MPH? Has the current prop ever been repaired? What is the size of the current prop?