2010 MCX running soft

jwroblew

I've got a 2010 MCX running soft the second half of the slalom course. Runs great with no skier behind the boat, will run 40+ all day long, idols fine, will rip your arms off when getting a skier out of the water. 1st half of the course runs fine gasses fine when the skier pulls but buy ball three when you go to gas it doesn't respond and by ball four forget it. Happens with Zero-Off on, Zero-Off in RPM mode and even when hand driving with Zero-Off off.

I've checked fuel pressure, its 59 to 60 PSI from idol to WOT and when pulling a skier, which I believe is in the range where it should be.

I've got a few ideas but wanted to see if anyone would come up with something different. I wish I had access to a scan tool but I don't.

Horton

@Jody_Seal‌

Horton

@ShaneH‌

Jody_Seal

I get that from time to time. Ask a customer how many hours on the craft? When was the last time it was serviced? before I ask about their initial problem. older (2010 Funny) boats that get Decent run time 150-300 hrs a year can loosen up well and need a good thorough inspection, clean out/up and tighten up. Especially if they see road time on trailers.
I would be looking for clean grounding, adequate or correct voltage to unit. did you run through the ZO Diagnostic's? What version are you running? Are their any known glitches with that version? is their any other problems at the dash? Did the Receiver pucks get swapped at their harness connector's? was a known good receiver puck run as a test? ( now we all need to have third in possession.) Is the second half of the course up hill?

jwroblew

900 hours, zero issues until this. I'm pretty positive that it's not ZO related since I tried hand driving, and still had issues about the second half of the course. All grounds seem good, etc. motor has been serviced regularly.

Andre

So it's NOT Zero Off related...?
I know there is a potentiometer in the throttle by wire system.Could it be bad,sending wrong info to the engine computer?
Is your throttle lever slowly creeping back toward neutral?
The fact that it still do this while hand driving is weird...
Good luck!

Dano

I may be out to lunch here but a suggestion would be to take a look at your exhaust pipes. If there is a clogg in there somewhere (muffler, pipe, CAT) it could be building up pressure causing your lack of power, as it can not breathe properly. I recently had a truck with a plugged CAT. Same symptoms. idle fine, accelerate fine initially, then hits a wall and no power.

Than_Bogan

I'm the last person who should be giving engine advice, but that sounds so weird that I want to comment and ask some more questions that perhaps will help someone who DOES know something about engines.

If hand-driving, the boat doesn't "know" where it is in the course, so it can't systematically do anything (right?). Could it really be that it just happens to get some cumulative effect at roughly that same spot every time? Have you tried pulling a skier on open water and is there a similar thing happening after just a few pulls by the skier?

When I first read the post, my immediate thought was something wrong with the course dimensions. But when I re-read, I can't come up with any way for that to actually explain the symptom.

I'll be very interested to learn what is happening. Very strange.

jwroblew

One other piece of the puzzle. With light skiers, everything is fine. For a 34 mph skiers it's not as bad as 36 mph skiers. And if someone has a big turn somewhere it happens earlier. I do think it is some cumulative effect.

Jody_Seal

Aw yes Hand drive and still persistent! was a diacom report performed? Was a fuel pressure gauge installed under load? Fuel quality? Cap and rotor changed or original? If cat's were backed up or exhaust blockage I would assume the 02 sensors would reflect that condition. Up hill courses will cause havoc!

jwroblew

Unfortunately I don't have access to a diacom, but if someone in the Phoenix area has one and will let me borrow it...

Original rotor and cap, that is on my list to change, the contact points of the rotor are a little carbon-ed up but not horrible. Yes fuel pressure gauge was installed under load and never fluctuated more than 59 to 60 psi. Fuel quality was good as well.

Thought about exhaust blockage but would expect more of an issue all of the time.

I was thinking maybe the MAP sensor?