X-Star 2004 MCX 5.7 350 - Really bad acceleration

[dom.xstar]

Hello together,

I bought a X-Star last year and currently I have still a problem with the performance.
My friends Mastercraft of 2008 has even more power (achieves speed for wakeboarding in a few seconds).
With my one, it takes currently about 30 sec. (and more) to achieve the wakeboarding speed (without any ballast).
About 24 miles per hour -> rpm approx. 3100
Engine Indmar MCX 5.7 350

What I did actually:
- Replace of spark plugs (original ones)
- Replace of injectors (original ones)
- Checked air filter (ran without)
- Measured fuel pressure: 50-55 PSI

What else I can do? How about software or check for failures?
I have actually the propeller with 14,75 x 15,5 installed.
Next few days I want to install 13,7x 17 -> Should be the original on, dealer said.

Hopefully you can help me I should check also.
Can believe Mastercraft sold a boat with a performance like this in the past.

Looking forward to your advices.
Regards

[DBUSH36]

I have the same boat and the only time I see acceleration anything like that at all is with stock plus 4500 aftermarket ballast full. Something is wrong for sure. Did you do a compression test on all cylinders. Sounds like you might be running on 7 not 8


Sent from my iPhone using Tapatalk

[dom.xstar]

Thats what I am wondering about. Last time we ran with three people and one wakeboarder behind and without any ballast.
How can I check this? But normally, if one cylinder is not running, it should smell for gas?
How can I do a compression test?

[DBUSH36]

Just sent you a pm


Sent from my iPhone using Tapatalk

[88 PS190]

Should do compression test regardless disconnect the coil - remove a spark plug (which you know how to do already) and thread in the compression tester, then you spin the engine over a few times and read the gauge. Write down the numbers - you're looking for good compression on all 8 with a similar number on all 8.

If one cylinder is not running... Start the engine and using a pair of heavy rubber gloves pull off one spark plug wire at a time. If the engine stumbles/runs worse then that cylinder was OK - if you pull one off and it sounds the same - well you found your bad running cylinder.

With the engine off check for the free running of your prop/shaft it should turn very freely in neutral. It is always possible to have a fouled prop shaft, fishing line in the strut or just a poorly aligned engine rob you of power.

Check and verify the operation of the throttle and cable - make sure that full throttle is opening the throttle fully.

They will also do this if they are not timed properly.

[37tr3n5k]

https://www.mastercraft.com/teamtalk/showthread.php?t=100738

I'd read thru the troubleshooting guide in that link. It saves lots of time. Its for your engine. I'd start at 7-8.

[dom.xstar]

Following you will find a video of the current performance: https://youtu.be/rMYoVU2kyus
Propeller 14,75 x 15,5 is installed.
It reaches the rpm's quickly but the acceleration is really bad. I was alone on the boat without any ballst, only gas tank is filled up completely.

Yesterday I installed the original propeller: 13,7 x 17 -> Even worth!!

Before I cleaned the distribution cab. Litte bit of corrosion found, but nothing changed after cleaning.

Next step will be to check if every cylinder is running and also the compression test.
Takes I while because I have to wait for the device to test it.

Anything else I could check?

[dom.xstar]

Additionally, the following gear setup is used:
ZF 63 IV
A: 1,56
B: 1,57
How is the total ratio of it by the way? 1.56 x 1.57 = 2.449 ??
Or 1/1.56 x 1/1.57 = 0.408 ??

[snork]

distributor cap is toast

[dom.xstar]

Okay seems like.
Call you tell me which one it is?
I guess I do not have to order it at Mastercraft?! Is it a GM one?

[dom.xstar]

Knows someone which one with rotor I have to order?
I guess it's a one of Vortec 5.7!?

[37tr3n5k]

Just take it off and take it to an auto parts store. Theyll Match it. It is not specifically Mastercraft. It is just a GM 5.7 cap and rotor.

[wheelerd]

A couple of other questions:
- Does the boat start easily? Both when cold and when warm?
- Does it rev quickly when in neutral? Does it stumble or lag?
- How old is the gas in the tank?
- Once you are up to cruising speed and nail the throttle does it respond immediately or bog?

If the dizzy cap is pitted like that be sure to check the rotor as well.

[dom.xstar]

Okay, let me talk with some shops they sell car parts.
I will change the cap and also the rotor. Could this condition cause any bad performance


Regarding you questions:
- I would say yes, it starts immediately. But sometimes the rpm’s after the start a little bit less and not constant.
Struggling a bit and after a few seconds it runs continuously and as is should -> But it’s not happen every start.
- Yes it rev quickly but for my feeling it could be a bit quicker / more aggressive.
- Gas is three weeks old
- I would say it bog but let me check today or tomorrow

[mtajpa]

I have an LTR not MCX but have you checked to see if the "KNOCK SENSOR" is connected. It is usually in the port block drain. Usually it is disconnected to winterize. This sensor could cause low performance if disconnected. Its purpose is to retard timing for low octane fuel in believe.

Also check for bad plug wires. Run at night look for sparks jumping off wires and ticking sounds.

The trans ratio's are A=1.56/1 in forward B=1.57/1 in reverse.

Good luck.