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hethj7

M5/M6 Impeller Replacement.

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ahopkinsVTX

Good write up. Thank you. I pinned this for easier reference. 

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timmypop

I am surprised there is not more conversation on this after hearing how much of an issue it is with my local dealer. I did some searching on the forum, but didn't see any major conversation about this problem. 

I was having dinner with my good friend who works at my Bu dealer and he mentioned how common it is becoming on the M5/M6. The very next morning it happened to me on my 2020. I immediately smelled burning and my temp skyrocketed. Worst part of changing it was how hot the motor was. I recommend adding some gloves to your list above. Constantly burning my hands. I hope Malibu will get a fix for this soon as it did put a damper on getting some good morning water. 

I have a video my dealer shot on the replacement process since it becoming so common. I will see about getting permission on posting it. Would be cool to download it to your boat. 

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hethj7

It is all over the FB page, but no one really knows the percentage of occurrences.  Certainly like anything, most people will post the issues vs a post that says “hey, everything was great today”.   

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Murphy8166

Thanks for posting this - I am at 46 hours and want to replace mine. 

Ordering a pair of pliers this eve and making an on water impeller tool kit. 

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Eagleboy99

Great write-up but Holy Hannah!  Who  designed that pump placement?

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Sparky450

I am going to say I have 280+ hrs on mine and have only had one impeller problem, and that was about 10 hrs after my sea strainer plugged up. I had changed it at the 10 hour service. Then I went to approximately 260 hrs. 

I will also recommend a ratcheting box wrench to get the bolts out. It makes it a lot quicker. 

https://www.amazon.com/GEARWRENCH-16-Inch-Combination-Ratcheting-Wrench/dp/B0002NYCYU

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dcarl

My experience is similar to @Sparky450 I replaced mine but only after my sea strainer got plugged with sand. I've only put another 25hrs since then but have had zero issues.

 

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bcoppess23
5 hours ago, dcarl said:

My experience is similar to @Sparky450 I replaced mine but only after my sea strainer got plugged with sand. I've only put another 25hrs since then but have had zero issues.

 

My dealer made a comment about needing to keep an eye on the sea strainer.  Does anyone think that is causing more problems, causing the impeller to run dry?  

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ahopkinsVTX
15 minutes ago, bcoppess23 said:

My dealer made a comment about needing to keep an eye on the sea strainer.  Does anyone think that is causing more problems, causing the impeller to run dry?  

My thoughts are no. I’d rather take the time to check the strainer than the impeller. If the strainer is catching a lot of crap, you are preventing that from getting in your impeller and the rest of the system. Of course if you don’t check the strainer you could clog the system and burn your impeller up. If you don’t have a strainer you may tear your impeller up and or clog up the heat exchanger. There is no perfect system when using raw water for cooling in my opinion. There is always trade offs and pros and cons.

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bcoppess23
10 hours ago, ahopkinsVTX said:

My thoughts are no. I’d rather take the time to check the strainer than the impeller. If the strainer is catching a lot of crap, you are preventing that from getting in your impeller and the rest of the system. Of course if you don’t check the strainer you could clog the system and burn your impeller up. If you don’t have a strainer you may tear your impeller up and or clog up the heat exchanger. There is no perfect system when using raw water for cooling in my opinion. There is always trade offs and pros and cons.

I may not have worded my question/thought clearly.  My thought was, are the strainers doing their job, but happen to become clogged easier on the newer boats therefore, causing the impellers to run dry and fail?  Could the newer motors have more sucking power and are picking up more debris, or smaller grates causing debris to not pass through and clog it easier?  The scenario my dealer was explaining of how he had to constantly check that and make sure it was clear made me stop and think, on my '14, I never thought to check that or even consider it as a potential first problem with over heating.  Regardless, never had an issue with my 350.  Now, soon to be going into a '21, I am slightly worried but am also better informed and will monitor things differently.  

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wdr
Posted (edited)

The strainer screen appears to have slightly bigger mesh holes on my '19 compared to the after market one I put on my '10. But the '19 version IME, has been more than capable of doing the job it was intended to do, regardless of the gph getting pulled through it. I boat on a river and there is a constant flow of crud suspended in the water do to the daily water level fluctuations and I have never had an issue with either version. The core holes in the heat exchanger appear to be many times larger than the debris that would be passing through the screen so I am not really worried about it, but I do check the screen frequently. It appears that all of the impeller failures were due to just bad impellers, at least I have not read where there was a mention of a clogged strainer as a contributing factor. What I would be curious to see is if anyone else has a kink in the raw water hose between the ball valve and the sea strainer? I have/had a kink that was constricting flow by no less than 1/3 because the hose was too long between the 2 points. I have since placed the equivalent of a pipe patch on it to get the hose opened up. I don't think it cut water flow significantly as I never saw a crazy temp swing on the gauge, but it was kind of scary staring at a 45 deg bend in the hose.

Edited by wdr

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dcarl
5 hours ago, bcoppess23 said:

The scenario my dealer was explaining of how he had to constantly check that and make sure it was clear made me stop and think, on my '14, I never thought to check that or even consider it as a potential first problem with over heating.  Regardless, never had an issue with my 350.  Now, soon to be going into a '21, I am slightly worried but am also better informed and will monitor things differently.  

I agree on my '16 I never had to clean my sea strainer.  I use my 2020 on the same water in the same way, granted its larger VTX vs LSV.  Now I check my sea strainer regularly and have had to clean it out twice now. I thought maybe they changed the location of the fresh water intake but it seems to be in roughly the same place.  I know it shouldn't make a difference but could it has something to do with the placement of the sea strainer?  On my '16 it was under the rear seat and on my 2020 they moved it to the back presumably to make it easier to clean/inspect, just thinking out loud.

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shawndoggy

wow I see what you guys are talking about now, having watched that video.  kind of a bummer on the design, especially for a pulley driven water pump to do it that way. The PCM pulley driven setup is a piece of cake and I really like how you don't need a puller to change the impeller. You do have to loosen the belt tho, which I guess can be moderately confusing the first time.

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jcon44

"Be careful as these bolts and washers are very easy to drop and then very difficult to find. I actually carry spare bolts now on the boat since I usually drop one.  "

Does anyone know what size/thread pattern the bolts are? i would like to have some spares but i'm trying to avoid pulling one to take to the store and didnt think of it when i had it apart. Thx,

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Pnwrider
1 hour ago, jcon44 said:

"Be careful as these bolts and washers are very easy to drop and then very difficult to find. I actually carry spare bolts now on the boat since I usually drop one.  "

Does anyone know what size/thread pattern the bolts are? i would like to have some spares but i'm trying to avoid pulling one to take to the store and didnt think of it when i had it apart. Thx,

https://www.bakesonline.com/johnson-impeller-raw-water-pump-housing-screw-only.html

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hethj7

If I can still read the writing on the hardware bag I will try to check tonight on the bolt size when I am at the boat.  

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hethj7
10 hours ago, pauley71 said:

That's for the Johnson .. does that fit the new M5/6?  I thought it was a different pump.

Confirmed, they are the same bolts.  I bought M5x.8x10 and M5x.8x12 as I couldn’t match the length quite up to the stock ones at the hardware store.  Turns out that is because 7/16 like Bakes has is between the two lengths.   I ended running the 10mm ones and haven’t had any issues.   

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G Spot

That’s a good video.
 

I’ve changed the impeller on my M6 once by removing the pulley and the second time when the impeller was destroyed on the water where I didn’t remove the pulley. The impeller comes out super easy when when it’s destroyed and nice and toasty.

In short I would try to remove impeller first without removing the pulley. 

Also, removing the lid of the heat exchanger seems like a pain. I was able to get my impeller pieces out by sweeping the pieces near the hose with my finger and using a needle nose pliers to extract. Might help save some time. 

Edited by G Spot

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hethj7

Agreed, I did mine without dropping the belt and that was on an impeller that was intact.  

As a reminder for those that do end up dropping the belt, below is a shot of the belt routing in case you need to see it for reassembly.  This is from the PDF manual loaded on the boat’s main screen.  Dropping the belt also requires more tools onboard as you will need a 1/2” driver or breaker bar for the idler pulley to rotate.  
 

 

5D5F2BBA-0706-4576-9660-E94A3E873686.jpeg

Edited by hethj7

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agarabaghi
22 minutes ago, G Spot said:

That’s a good video.
 

I’ve changed the impeller on my M6 once by removing the pulley and the second time when the impeller was destroyed on the water where I didn’t remove the pulley. The impeller comes out super easy when when it’s destroyed and nice and toasty.

In short I would try to remove impeller first without removing the pulley. 

Also, removing the lid of the heat exchanger seems like a pain. I was able to get my impeller pieces out by sweeping the pieces near the hose with my finger and using a needle nose pliers to extract. Might help save some time. 

Might not have it on the water but a shop vac works great for sucking out the pieces from the hose opening.

 

I will be using this impeller at 150hours when I pull out the stay cool pump one. Jmp 7352k-01 they use flex wax infused rubber. Looks much different

 

 

 

 

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agarabaghi
Just now, hethj7 said:

Agreed, I did mine without dropping the belt and that was on an impeller that was intact.  

As a reminder for those that do end up dropping the belt, below is a shot of the belt routing in case you need to see it for reassembly.  Dropping the belt also requires more tools onboard as you will need a 3/4” driver or breaker bar for the idler pulley to rotate.  
 

 

5D5F2BBA-0706-4576-9660-E94A3E873686.jpeg

Isn’t it a 1/2” driver?

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