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Problems w/ LT4 not having enough power


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I picked up my 2022 25 LSV and on the first day out could not believe the additional power it had.  It was more than enough.  Well the wind has been crap this year and the lake are full and choppy so being  primarily a wakeboarder I did not put many hours on it for the first couple of months.  But then had a few other issues to take care of so brought it in during the time we were out of town and not using it.  I get it back and was excited to take it out and load it up but when I filled everything with an additional 300lbs of lead and 3 people it would not get on plane even in lift mode set full time.  It would get to about 17mph or 18mph and acted like a regular old monsoon 350  was pushing it.  It obviously is not in limp mode or it would not go that fast.  I figure it is either the supercharger belt slipping or a software issue because the rpm's start aggressively increasing quick and then cut back drastically limiting them to around 3400 rpm's until it gains a little more speed.  Unweighted it gets up and goes like normal and can even get up to 47 or 48 mph with the standard prop.   When surfing I have to drop weight to about 3/4 full and it eventually (very slowly) climbs to the set speed.  So we can technically surf but not wakeboard unless I dump more than half the ballast.  It did not do this before and even my demo ride on the same boat got up to speed quicker with the M6.   What the hell could be going on?  It has been to the dealer 3 times (replaced the SC belt) and they are stumped as to what could be going on as there are no codes.    It did blow a hose off early on spraying coolant in the bilge and I thought that may have caused the belt to be slipping but nothing else significant has happened to have caused any issues.   What is going on?

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4 minutes ago, bigskydoc said:

Have you tried it with the cruise control turned off?

Yes,  It basically throttles a percentage of what is asked of it which is why I assume it gets up to full speed with nothing in it and no speed set.  So for example when I set it at 11 mph to surf it never gives it full throttle it seems like it gives it like 35% to 40% of what it is capable of and just stays steadily climbing at that less aggressive rate until it tops out based on the amount of weight in it.  So it seems more aggressive initially with no set speed.  It does not matter what the throttle aggressiveness setting in the settings are set to.

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No codes at all?  Seems like the ECM is derating the engine like it's sensing a knock condition or something.  There's no chance you got water in the gas while it was sitting, right?

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Check to see if there are any codes that have been thrown via the screen on the left.  It sounds similar to a knock condition and preventing the boat from putting too much a load on the engine.  In that same screen, check the Engine Diagnostics screen to see what the engine load is unloaded and cruising (48 mph) vs. the load on the engine trying to surf/wakeboard. 

I had a similar problem you are explaining.  It was knock related and after verifying, it was bad fuel.  Had to replace the fuel filter and clear the code.  Best of luck.

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I'm wondering what happens if you ballast it up for surfing, turn off the cruise control/ speed control, and then slam the throttle forward.  Conversely, what happens if you run it empty, but with speed control set to 11MPH? 

I've noticed that the GPS speed control, on my '22 M220, is a lot slower at getting up to speed than my paddle wheel speed control on my '17 22MXZ was, but if I turn off Speed Control, the new boat is much faster at getting up to 12 mph.

Likely this is not the issue, but just trying to think of things that may not have been thought of.  It would be interesting to capture live codes as it sounds like you are losing boost, or have a case of bad gas.

Edited by bigskydoc
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2 hours ago, UWSkier said:

No codes at all?  Seems like the ECM is derating the engine like it's sensing a knock condition or something.  There's no chance you got water in the gas while it was sitting, right?

No codes at all.  It was a fresh  104 gallon tank from a reputable gas supplier so no water that I know of.....  maybe the gas was bad for some reason but I guess I will have to take it back to the dealer and get the diagnostics sent to Malibu.  I sent a video of it under load not getting up to speed which they were going to forward it to corporate along with diagnostics the last they saw them.

@bcoppess23  great suggestion looking at what it is doing under load versus at speed.   I will check that next time out.   BTW, why did you have to change the fuel filter?

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I have seen performance issues on forced induction motors when the supercharger belt slips.  The most common cause is from an excessive amount of water in the bilge causing the belt to slip.

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Sure you aren't propped wrong?  If it does fine unloaded, and gets up to 47/48, you may just be propped too much for top end speed.

 

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13 hours ago, Gene3x said:

No codes at all.  It was a fresh  104 gallon tank from a reputable gas supplier so no water that I know of.....  maybe the gas was bad for some reason but I guess I will have to take it back to the dealer and get the diagnostics sent to Malibu.  I sent a video of it under load not getting up to speed which they were going to forward it to corporate along with diagnostics the last they saw them.

@bcoppess23  great suggestion looking at what it is doing under load versus at speed.   I will check that next time out.   BTW, why did you have to change the fuel filter?

Had to replace the fuel filter due to water being in it.  I never had problems with water in the fuel from this specific station with my previous boat but likely had a batch of bad fuel and the new boat didn't like it.  We didn't notice it until on vacation at Norris.  We could run fine unloaded but as soon as we would load the boat, it would act up and throw a knock code.

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10 hours ago, dhcomp said:

Sure you aren't propped wrong?  If it does fine unloaded, and gets up to 47/48, you may just be propped too much for top end speed.

 

Not propped wrong.  Have you felt one of these boats with the LT4 in it?  Over 600 hp and over 600 lbs of torque.  I have the standard prop.  Most people use the speed prop which will get you well over 50 mph.  Plus the M6 weighted heavier than mine with the same prop jumped out just fine.  Also, mine was doing just fine when I first took delivery a few months ago.  I only have had it up that fast 2 times just as an experiment.  Once when I first got it (when the hose popped off)and once to see if it would do it again after the power seemed off.  It isn't the prop.

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1 hour ago, bcoppess23 said:

Had to replace the fuel filter due to water being in it.  I never had problems with water in the fuel from this specific station with my previous boat but likely had a batch of bad fuel and the new boat didn't like it.  We didn't notice it until on vacation at Norris.  We could run fine unloaded but as soon as we would load the boat, it would act up and throw a knock code.

So it DID throw a code then?  That is what is weird about mine.   No codes! 

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9 minutes ago, Gene3x said:

So it DID throw a code then?  That is what is weird about mine.   No codes! 

Yes, it did throw a code at times.  But, the behaviors of yours are similar to mine.  I am running the M6.

 

A few events that would happen during this time are:

  • Throwing a code
    • Speed would set for wakeboarding or surfing
    • Code would throw causing the speed to disengage and slow the boat down
    • Then it would work itself back up to speed and re-engage speed
  • Not throwing a code - surfing
    • Would get to speed, speed would set 11.2
    • Load on engine would be approx 85%
    • After a 15-20 seconds of being stable, load would jump to 97%, exhaust note would change, and slow the boat down to 10.0
  • Cruising
    • I could throttle up and on plan and run WOT without issues

If yours is not throwing a code, as other mentioned, if there is a significant load on the motor, there could be slippage on the belt...  But, with it sitting a couple weeks and a change in behavior it is likely a few things, bad fuel, a change the dealer made when they were doing the service work (assuming 10 hr service), or a belt slipping.   My understanding on the 10 hr service, there is a lot of work that happens with motor alignments and such.

I hope you are able to find a quick solution!

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Does anyone happen to have a pic of the belt routing on the LT4?  Would be interesting to see how they wrapped the S/C pulley.  Also, a cheap boost gauge would help ID if you are having slippage issues (assuming there is a port you can jack into in order to get a reading).  Is there a Gatorback belt that can be used on that engine?  

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If there is slippage on the belt it seems like the computer would pick it up.  It is back in to the dealership and their hope is that a Malibu engineer will have time to look at it when he comes in for a different boat with different issues.  I discussed the wedge with them and the fact that it seems to be a software issue because it pulls back torque after I initially push the throttle for less than a second.  I can audibly hear the exhaust change and feel the boat cut power a little after pushing the throttle.    I mean I have taken 4 sets behind this thing so far total and 3 of those are with reduced ballast so i am starting to get pretty worked up here.   I never would have sprung for the LT4 if I knew this was the result.  BTW....  calculating the costs of gas and tolls trailering it to and from the dealer so far is well over $700 not including my time.  This is not an exaggeration at all.

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