Mastercraft Engine Options

[Glock]

Hey all. I am looking at purchasing an X7 and have some questions about engine options available. The boat I'm looking at has the 310 hp Indmar predator engine. I also see other adds touting the MCX engine. Can you educate me on the engines. Pros, cons, fuel economy, etc. Thanks!

[jefflyman]

I bet theres alot of discussion over at MC team talk about that subject. Heck you could probably find piston weight in grams if you want there!

[jerseydave]

Glock, I have a friend with an X-1 with that 310hp engine, no lack of power even when weighted for boarding and fuel economy is really good.....a light X-7 will be even better and will have plenty of power. What year is the X-7?

Teamtalk forum is the best place to ask anything Mastercraft as Jefflyman stated.

Just curious, did you shop on ski-it-again.com for used promo boats? There are some great deals on there.

[ForrestGump]

MCX is way overated at 350hp. In all actuallity, it comes in at about 310hp also.

[Chuck_Dickey]

I have to disagree with Shane. I had a 310hp predator in my 2003 PS-197 (same as X-7) with a 1:1 trans. Boat worked great except on lakes with a short set up. Struggled slightly when pulling heavy short liners, more so with three people in the boat.

 

I now have the 2011 PS-197WTT with the MCX motor and the 1.26:1 trans and I was shocked at what I had been missing all those years. No more struggle and much better gas milage to boot.

 

A big difference you have to drive it to see for your self.

[6balls]

If you drove Razor1's MCX you would think it was under-rated. I have a buddy w/the northstar caddy that's supposed to have so much power and Razor's boat leaps by comparison and stronger through entire range. Only spot it loses is a couple mph top end.

[ForrestGump]

It's common knowledge in the MC dealership network that the MCX was overated. Just went back and looked at my notes. 325 hp is what it dyno'd at. Now the question is, what other engines were over rated by Indmar?

[boarditup]

The torque curves between the predator and the mcx are basically identical up to about 3000 rpm. The Power Slot does make a huge difference. If it were me, the Predator/Power Slot combo is hard to beat for the cash.

[east tx skier]

What Shane said. I know a a guy who used to own a MC dealer who dyno'd an MCX and got 311 hp. Add the exhaust tips into the equation and it's probably sub 300. The base MC vortec 350 engine was always a good engine. Great mid range torque. The MCX is a fine engine, too. But 350 hp it is not.

[east tx skier]

If I had to choose between hp and gear reduction, gear reduction would win every time.

[Chuck_Dickey]

I was told the Preditor was under powered for the reduction transmission and the MCX or the Caddy motor was the bomb. Having owned bothe the Preditor 1:1 and the MCX Powerslot 1:26:1 I'd have to agree, the trans makes the boat super

[vtjc]

I ski with a friend with an 05 MC 197 with the 310hp w 1:1 trans, its the slowest boat on the lake out hole, I would recommend the PowerSlot or larger motor as others recommended above. The 197/X7 hull is fairly heavy for a ski boat with a fair amount of drag. I had the 310hp w 1:1 trans in my '99 MC CB SportStar(95-97 ProStar Hull) and it was a very strong boat.

[DooSPX]

I agree with east tx skier, I would vote for the gear reduction over a slightly higher HP boat with the 1:1. My 91 MC PS190 240hp w/ the 1.52:1 felt as strong as a 285hp 1:1 I skied behind. Also Now with my OJ CNC 4 blade, its even better. Also, a buddy has a 2010 Moomba Outback with the 325hp 1:1 factory 13x13 3 blade, That boat really feels weak out of the hole compared to my PS190 but is faster mid-topend by a bit.

[east tx skier]

I had it explained to me like this. The only reason for the 1.52:1 gear reduction is to be able to turn a bigger wheel. The size of those old school power slot props was nuts. 14x18 or 16x18 IIRC. Couple that with those light early 90s boats and the hole shot was insane, forget the horsepower. With the newer boats (hooked 197 and 200 to be precise), there is a lot of wetted surface to push around. The 1.52:1 is gone and the lower gear reductions of 1.22, 1.23, 1.25 and 1.26 among MC and CC (CC being the 1.23) are turning 13" diameter props IIRC. So horsepower is the way to make up the difference. But even so, for the tournament boats, it's more a factor of wake and pull tuning. MCs use a different gear reduction depending on the engine and put a prop in to match. They are basically shooting for an rpm sweet spot at skiing speeds (presumably 36 and/or 34 mph for the best performance sweet spot).

[boarditup]

The faster you spin a prop, the more drag it creates. Drag robs the torque curve. Gear reduction allows the curve of the motor to match the curve of the prop with the drag of the vessel cutting through the water and the air. Additionally, the more blades and the greater the surface area, the drag goes up. You need some drag for the prop to work - that is propulsion. The selection of the prop and the gear reduction is an art form in the compromises it makes for the entire boat speed spectrum.

 

Hole shot is basically a function of surface area and drag versus the torque curve. Reducing pitch will allow the motor to spin up faster and get going sooner, but at the cost of top end. Adding cup to the prop allows a bit of both. Gear reduction allows for greater surface area and pitch while spinning the prop slower to avoid drag caused by blade speed.

 

So, on the 197, the Power Slot allows the 5.7 V8 variants to perform almost identically up to about 2,700 rmps and then the MCX breathes better and has more power at 34-36 mph. With 1:1 drives, the MCX has a bit of an advantage, but not much.

[Razorskier1]

I can't speak for other boats. My 2005 MC 197 TT with MCX and power slot is incredible out of the hole and at speed. WIth the switch to 3 blade Acme it is now even stronger out of the hole and runs over 46mph at the top. My first set this year I was reminded that it pulls like a freight train to 34mph. I mean you get pulled up and it feels like it is trying to pull the handle out of your hands the whole time until it hits speed. So my guess is there was a lot of variation in the engines. A friend who is a MC mechanic tells me that Indmar had a guy who used to be responsible for checking and tuning all engines who left after 2005 and the engines suffered. He said it was the dumbest thing Indmar ever did to let this guy go. Don't know anymore than that, except my engine runs like a raped ape.

[6balls]

I confirm Razor1's raped ape boat.

[east tx skier]

I have a friend with a 2005 TT raped ape. Quite a pull.

[Laz]

@DooSPX tell your buddy with the 2010 Moomba to,change his prop. I switched to an ACME 3 blade (the one they recommended and I can get the exact model if you need it).

 

I always wondered why my Outback didn't feel as good as the other ski boats. Then I changed props. The hole shot improved dramatically and the top speed improved. In fact, when I redid the Stargazer baselines, the RPM was about 200 lower.

 

Maybe this is because the ACME props have a different design with much more surface area. Regardless, the improvement was dramatic.

[DooSPX]

@Laz, I have told him to switch props, He was speaking with Eric from OJ on the matter... Then he had a baby and the boat went on the back burner.

[eleeski]

My 04 MC had a great hole shot but hammered you in the slalom pull. Switching to a taller prop made the slalom pull much friendlier. I will trade away hole shot Gs for a couple more buoys in the course.

 

Efficiency of the prop is a minor factor for a ski boat with all its excess power (unless you have a Nautique 200 which has sooo much drag). The bigger props on the old Powerslot vs the flat hulls gave a better slalom wake - that drove the reduction transmissions - not a need for more power. Prop tips will cavitate so you need to tune the rpms to the prop diameter and the engine redline. 4 blades transfer more power but are less efficient than 3 blades. Three blades seem to make better trick wakes.

 

Tuning a prop for your skiing level and style is an art. There are lots of tradeoffs.

 

Eric

[Razorskier1]

My 3 blade Acme is better all around than the 4 blade factory OJ. Boat as more hole shot, more acceleration, more top end and as mentioned by @Laz , it runs about 200 RPM lower in the course, which should mean gas money! Love the Acme.

[Glock]

Wow, thanks for all the advice. It sounds like there are alot of different opinions out there and that if the engine, transmission, and prop are all working efficiently, both engine options work quite well. Thanks for all the advice, I love this forum!

[jipster43]

@eleeski I'm reminded of the '93 Boaters Guide where they compared the '93 Prostar with three different engine/transmission options - 285 w/1:1, 285 w/powerslot, and the LT-1/powerslot. In this comparison the 1:1 threw the preferred slalom wake.... I still wish I had the LT-1/powerslot combination!

[usaski1]

@doospx -- I have not been happy with my outback prop... I think its causing a vibration at low speeds.. its the stock OJ nibral 13x13... want to put a acme 422 on it... (what most nautiques run) I think that will improve its holeshot and hopefully smoothness.. although the 325hp is not lacking power, it doesn't feel as strong as some other boats I have been in, with lesser motors. (an older 02 Malibu comes to mind)

[Laz]

This is the ACME prop I have(#541)

 

Outback 541 13 L 12 3b .080 C

[east tx skier]

@jipster43

 

Yeah, it was the 1:1 with the 351 HO in the S&S 190 IIRC.

[east tx skier]

@usaski1, if you put a 422 on it, you'll have to throw it into reverse to go forward. The 422 is RH rotation. Go with the 541 or similar like Laz uses or call Acme and ask for Bill Weeks. I ran a 541 on my old MC with close to 300 hp and a 1:1 and it was fantastic over stock. I also preferred it to the OJ XMP 13x12 I tested it against.

 

www.tylerskiclub.com/proptest.pdf

[usaski1]

Good call East TX Skier.. that would be a major screw up! I just dont want to spend $500 and have almost no improvement. In either vibration or holeshot.

[jipster43]

@east tx skier Sometimes I speak my own language. 351 HO - 285 HP! Thanks for clarifying that Easty!

[Ed_Obermeier]

@jipster43 wrote

...I still wish I had the LT-1/powerslot combination!

 

One of my best ski buddies has a sweet '95 PS190 with that combo, 310 hp rated. I have the good fortune to get to ski behind a lot of different boats, this is definitely one of my favorites. Fun to drive and great to ski behind.

[DooSPX]

My OJ CNC #454 4 blade did wonders for my boat as I said, but not only did the hole shot improve, it make the boat feel a little more forgiving behind the boat. IT also flattened the bump a bit, and felt like it made the wake a little softer (this could be in my head). Lastly, it lowered my rpm by about 200 rpm. When I called Eric, I told him I wanted everything listed above, and the prop delivered!

[usaski1]

454 looks to be a wakeboard prop?? Was it any smoother? the stats list it as 13.7X17.5L4XMP-1-1/8" (XMP-454). Bigger numbers are higher pitch? I have a 13x13 now. I have brought this up before, but I want smooth.. and more holeshot. will going from a 13x13 to 13x17.5 deliver? I don't understand the numbers...

[east tx skier]

He has a powerslot IIRC. So that prop isn't going to work for you on your 1:1. The 541, in my experience, pulls a lot harder out of the hole than the comparably sized OJ XMP 13x12. Check the link above for my specific findings in comparing these two props. OJ suggested that a 13x11.5 would be a closer comparison, but it seems like that might rob you of your top end. The OJ had a slightly softer pull, but it was not enough for me to want to change props. The Acme hit harder out of the hole six days a week and twice on Sunday.

 

The absolute best thing you can do is try before you buy. Acme and OJ used to offer trial periods. I'm not sure if they still do. What some guys on a forum (myself included) is just what worked for them. I have compared them and I can't say one is better than the other. If you compare them, you can find out what works best for you. I would not, at this point, tell someone to go out and buy one brand over another. Having run props for your configuration back to back, I know there are trade offs between OJ and Acme. Only you can determine which is better in your application.

 

Probably not the answer you want to hear. But it's the most honest answer.