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Major Drop in RPMs


Swanyriver247

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Took my 2014 247 LSV (LSA)out this evening to watch the sunset in TX. When I bought the boat last July and up until about a week ago I could get the thing to run with the “mid range” prop to almost 5400 rpms and get about 46-48 mph. About a week ago I ran out of fuel, code surfaced about low fuel pressure afterwards, the mechanics came down ran the boat and cleared the code, no issues. I am at a loss because this boat (bought used with 155 hours) has been a tad bit of a nightmare. Unfortunately I’m handcuffed with a single Malibu dealer in the NTX area and to be honest we have not had a very good relationship. The boat now will only run up to 4200-4400rpms and can barely make 35mph.. What can be the issue? Is it a possible supercharger failure, a fuel pump issue, it’s almost like the prop was swapped for the Torque model instead of the mid range (2249) that I had in the beginning. Any help or input would really be greatly appreciated.

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running an engine out of fuel isnt a problem.  Running a TANK out of fuel is a problem.  You likely sucked sediment into the fuel system.  You can check for fuel pressure at the fuel rail (if there is a test port).  But, there is a difference between fuel pressure at idle and fuel pressure under full load.  You need to start at the tank and move towards the engine.  In-tank fuel filter?  In-line fuel filter?  Dirty regulator?  Partially clogged injectors?  Or you could have burned up the pump when you ran it dry.

If you have an issue with the people specifically at WSA in Lewisville, you can try their new second location in Ft Worth.  Still WSA, but possibly new/different people than you've dealt with before. 

Being a SC motor, i would be very hesitant about running the engine at all until you find the culprit.  Running a boosted motor lean NEVER ends well. 

Edited by Texan32
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Thanks much for this, seeing as they just serviced this and came back with no problems I think I will just haul out and drive up for one more chance.....

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The LS3 and LSA use a higher flow in tank fuel pump assembly than the other engines, so if one of the two fuel pumps failed you may have a loss of power, especially at top end.  If course, problems with engine cylinder compression, the supercharger, a fuel injector, or even a loose spark plug wire can cause similar running issues.

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1 hour ago, Swanyriver247 said:

Thanks much for this, seeing as they just serviced this and came back with no problems I think I will just haul out and drive up for one more chance.....

Even if they "serviced" the engine, unless they put it in the water and loaded the engine, its not truly tested.  An engine with no load will NOT pull the same amount of fuel that one in the water will pull. 

A partially clogged fuel system can certainly show a good pressure reading at the rails while idling or even being spun up with a fake-a-lake.  But once there is an actual demand on the motor, your pressure can/will drop.

CSKeaver is right.  All those things he listed are correct.  BUT, since your problem started after running out of fuel, the fuel system is where i would start looking for problems. 

You could also pull a couple plus and make sure you didnt burn them up.  I would expect them to show signs of a lean condition.

image.png.09d938ee61c4ed3bfc6a1422fa8538b3.png

 

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On 6/14/2020 at 2:23 PM, csleaver said:

The LS3 and LSA use a higher flow in tank fuel pump assembly than the other engines, so if one of the two fuel pumps failed you may have a loss of power, especially at top end.  If course, problems with engine cylinder compression, the supercharger, a fuel injector, or even a loose spark plug wire can cause similar running issues.

Well I took i up to the dealer, it was assumed that they only had one tech go to the lake visit and they dont suggest that single tech's go on lake to run/load a boat but to just run at dock. I was told that I was looking at 2-2.5 weeks on a service/repair for this and that was dependent on if Malibu was able to ship a new fuel pump due to COVID/Carriers. I worked on Sportfishing boats for 10+ years in my past and this is my first lake boat. I have searched high and low on fuel pump replacement and can not really find anything, is that an omen that dealers should only attempt this? From the looks of it, just seems like a plug and play situation after replacement so why not order a pump/gasket/filters from Bake's and have a go at it, will I find a slippery slope at any point in this challenge? Worst case scenario I have a new pump installed, new filters and if it works then full speed ahead, if that is not the issue then I have a new pump installed, filters etc but also have a reserve back up if needed and I stay on the work order list? 

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On 6/14/2020 at 3:08 PM, Texan32 said:

 

Even if they "serviced" the engine, unless they put it in the water and loaded the engine, its not truly tested.  An engine with no load will NOT pull the same amount of fuel that one in the water will pull. 

A partially clogged fuel system can certainly show a good pressure reading at the rails while idling or even being spun up with a fake-a-lake.  But once there is an actual demand on the motor, your pressure can/will drop.

CSKeaver is right.  All those things he listed are correct.  BUT, since your problem started after running out of fuel, the fuel system is where i would start looking for problems. 

You could also pull a couple plus and make sure you didnt burn them up.  I would expect them to show signs of a lean condition.

image.png.09d938ee61c4ed3bfc6a1422fa8538b3.png

 

I will also have this on the checklist as well if I pull the boat from the dealer and do any investigating, thanks much for this.

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On 6/14/2020 at 3:08 PM, Texan32 said:

 

Even if they "serviced" the engine, unless they put it in the water and loaded the engine, its not truly tested.  An engine with no load will NOT pull the same amount of fuel that one in the water will pull. 

A partially clogged fuel system can certainly show a good pressure reading at the rails while idling or even being spun up with a fake-a-lake.  But once there is an actual demand on the motor, your pressure can/will drop.

CSKeaver is right.  All those things he listed are correct.  BUT, since your problem started after running out of fuel, the fuel system is where i would start looking for problems. 

You could also pull a couple plus and make sure you didnt burn them up.  I would expect them to show signs of a lean condition.

 

 

Running out of fuel in an in-tank fuel pump is one of the worst things you can do as it uses the fuel to cool the pump/pumps.  I have seen several scenarios where fuel pump went out after running out of gas. Anyways I would check the system as a whole.

@Swanyriver247, I am not sure in yours, but most are basically automotive fuel pumps placed in the tank. Friends Mastercraft needed a new fuel pump after running out of fuel. The Mastercraft part was over $650.00. We simply took the pump out of the assembly and replaced with a new one and new filters, for $60.00 from auto parts store (left housing and replaced the pump only).

Not sure which pump you have but Bakes sells for $700.00. I would pressure test as stated above before digging further into it. I have not done this with an LSA pump either, but there should be two electric pumps in there to remove instead of whole assembly. The fun part would be matching it up at parts store if they need to be replaced (unless you can find an article where this has been done before). Then your wait is over as it would only take you a couple of hours DIY.

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I agree that a fuel pressure test under load should be done to see if the pumps are actually causing the running issue before just "throwing parts at it" until it works.  It is more time consuming to diagnose the problem first, but it is less likely a potentially expensive mistake will be made.

If the fuel pump does need to be replaced, it is better to get the complete assembly from a Malibu dealer, and they can check the boat build sheet and use parts references from Malibu to get the right one for your boat and engine.

Remember that fuel can be pretty volatile and dangerous stuff, especially if it ends up in your bilge.  It is common to do a fuel tank pressure test and inspection for leaks after a fuel pump is replaced to reduce the risk of leaks.  If you don't have the right equipment and experience to do the job, you may want to leave it up to a professional.

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4 minutes ago, Texan32 said:

Any luck getting your issue fixed?

Well, I grabbed the boat back from WA in Lewisville but kept it in queue for repairs. Did some driveway investigation and  got a fuel pressure gauge and attached that, but not under load. Only got 48-52psi out of it. I have ordered an LSA fuel pump, gasket and also filters for the boat. Should be in today, after a screw up in a direct ship from Bake’s last week. Gonna start with filters and go from there. I honestly have ZERO confidence for WA, and would be surprised if my boat could go in for service and actually get back to me before the end of the summer. Hopefully the “driveway” mechanic can get us back on the water...

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Pump replaced, new fuel filters and took it for a ride...... Unfortunately I was solo and could not run the fuel pressure gauge at the same time I put a load on the LSA....

long story short...... Not a change at all in the performance of the boat. We are testing the original Fuel Pump right now but I can tell you the fuel filters were s***ty, like almost non-serviced in my opinion... I will post pics tomorrow but I have come to the conclusion the Fuel system is not the issue.

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  • 2 weeks later...

I was finally able to get in to the shop and have them service it. One fouled plug was the diagnosis for the reason it was not turning up. According to the dealer these were original plugs and the previous owner never changed them as it is recommended at 300 hours, my boat was bought used with 155 and I just had my second 50 hour service done while it was in. I never had any missing on the motor, nor did the engine ever drop a code or enter limp mode which I guess would happen if the motor was missing/dropping a cylinder. Somehow also my prop was changed from a 15x12 to a 15x14.25 so they changed that back? And then to fuel the fire, the tech lake testing the boat kept hearing/feeling a clunk in and out of gear, so a nut on the strut cane loose and also play in the V-Drive connection had basically rounded out the key way and was about to “let loose” at some point so add another 1000.00 to the Bill with a new shaft. I have missed 6 weeks of the season with this boat and am really second guessing my choices.....

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