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Old 08-13-2022, 09:16 PM   #1
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Cummins 6BT5.9 water pump cam bolt sheared off

A friends Cummins water pump has had the bolt that holds the pump cam shear off twice now in the last month. Does anyone have any experience with this problem?
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Old 08-13-2022, 10:06 PM   #2
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I have had this happen several times on one of my trucks. In my case it threads into a blind hole on a bracket. It is fine thread so has to be a grade five or grade eight. Grade eight is much easier to find than a fine thread grade five. After way too many broken bolts I found that a grade eight bolt will easily fracture IF NOT TORQUED TO SPEC.
Eleven years ago I torqued it to spec and havenít had one break since.

How many broke? On one cross country trip of about five thousand miles I think it was four broken alternator pivot bolts.
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Old 08-14-2022, 08:11 AM   #3
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Quote:
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I have had this happen several times on one of my trucks. In my case it threads into a blind hole on a bracket. It is fine thread so has to be a grade five or grade eight. Grade eight is much easier to find than a fine thread grade five. After way too many broken bolts I found that a grade eight bolt will easily fracture IF NOT TORQUED TO SPEC.
Eleven years ago I torqued it to spec and havenít had one break since.

How many broke? On one cross country trip of about five thousand miles I think it was four broken alternator pivot bolts.

I assume they were over torqued when they broke?
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Old 08-14-2022, 09:37 AM   #4
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The new cam that broke the bolts allows the bolt to pass through. The old one bottoms out.
When the bolt is bottomed out in the old cam it doesn't move laterally. The new one move side to side a small amount. It may be vibrating and break
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Old 08-14-2022, 11:02 AM   #5
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If this is the "stock" Sherwood brand pump, I recommend changing it out for a new SMX 1730 pump from Seaboard Marine (sbmar.com). It is a far superior pump in almost everyway, and does not cost much if any more. It is a "plug and play" or direct fit. It comes with an impeller puller as well, making impeller changes easier.
There is info about the reasons why this is a better pump under "Tony's Tips" on this site (sbmar.com).

I am not affiliated in any way with this company (or any staff), just a happy customer.
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Old 08-14-2022, 11:07 PM   #6
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Never had this issue on either of mine. If the cam bolt is too long, it could be trimmed down or shimmed with washers. Have had no issues with the original Sherwood raw water pumps with well over 2,000 hours on each.

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Old 08-15-2022, 12:24 AM   #7
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I assume they were over torqued when they broke?


Under torqued. Just snug with a wrench.
To get the strength rated, the bolt has to be tightened to the torque value, less will allow it to break.
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Old 08-15-2022, 12:28 AM   #8
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Under torqued. Just snug with a wrench.
To get the strength rated, the bolt has to be tightened to the torque value, less will allow it to break.


Seeing the photos, my application is totally different. I pictured something else.
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Old 08-15-2022, 01:19 PM   #9
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Originally Posted by firehoser75 View Post
If this is the "stock" Sherwood brand pump, I recommend changing it out for a new SMX 1730 pump from Seaboard Marine (sbmar.com). It is a far superior pump in almost everyway, and does not cost much if any more. It is a "plug and play" or direct fit. It comes with an impeller puller as well, making impeller changes easier.
EXCEPT it's not quite plug-and-play for some 6BT 5.9 M engines. Mine's a 2002 and turns out the SMX has a notably higher flow rate than the original Sherwood. This means it's not appropriate for the 1.25" circuit without some modification for the inflow and output circuits. Yes, I know they have the photos of it mounted on a 6BT (see image). But it's also not retrofitted to a 1.25" circuit. Drop an email to the customer support folks at Seaboard and see if the SMX will work with your setup.

I had to go with another Sherwood for that reason. The retrofit cost would have been too much for the benefit gained. I'd be better off doing a repower. And if anyone knows who at Sherwood designed their back-assward water pump, let me know, would you? I'd like to have a word with them.



Drop an email to the customer support folks at Seaboard and see if the SMX will work with your setup.
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Old 08-16-2022, 08:47 PM   #10
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The SMX pump will work on your motor, and does indeed supply a lot more water than the OEM Sherwood.
Being a flexible vane pump, itís output can be restricted without damaging the pump, but do be sure all hoses and clamps downstream are in top shape, as they will be operating under more pressure.
Donít be shy about tapping raw water for other uses too.
I have seen impellor modified by cutting off every other vane to reduce output.
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Old 08-18-2022, 06:10 AM   #11
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Originally Posted by fryedaze View Post
The new cam that broke the bolts allows the bolt to pass through. The old one bottoms out.
When the bolt is bottomed out in the old cam it doesn't move laterally. The new one move side to side a small amount. It may be vibrating and break
Attachment 131192Attachment 131193


If the cam moves it will break the bolt. The old cam looks ok is there any reason not to re-use it ? Unless it is overly thin I would suggest using the old cam. The bolt should only retain the cam and not be under any additional load, if the new cam is moving you have a problem and the bolt will fatigue.
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Old 08-19-2022, 05:15 PM   #12
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If the cam moves it will break the bolt. The old cam looks ok is there any reason not to re-use it ? Unless it is overly thin I would suggest using the old cam. The bolt should only retain the cam and not be under any additional load, if the new cam is moving you have a problem and the bolt will fatigue.
We did re-use the old cam.
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