Engine/transmission mount bolt maintenance

[tedshred]

Hi all,

Can anyone provide some real world experience on how regularly engine mount bolt tension/torque should be checked and the suggested vs recommended tension/torque for my 2009 VLX Indmar Monsoon. Particularly the bolts that secure the mounts to the fibecs channels?

[dalt1]

Not talked about much. Most are loose but I don't think it is on the maintenance check lists. I tightened mine up 1 time after it was done under warranty. Get a small clunk when they get loose. Mine got done every other year. Torque will be very tough to get right as you can barely get to them with various wrenches let alone a torque wrench.

[tedshred]

7 hours ago, dalt1 said:

Not talked about much. Most are loose but I don't think it is on the maintenance check lists. I tightened mine up 1 time after it was done under warranty. Get a small clunk when they get loose. Mine got done every other year. Torque will be very tough to get right as you can barely get to them with various wrenches let alone a torque wrench.

Thank you. I have tightened all without a torque wrench. My main concern is not damaging the Fibecs channels by overtightening if that's possible. The issue I have experienced in the past was chewed out transmission mount bushings due to motor movement and the shaft coupling fell out of alignment. Keen not to repeat the experience.

[tedshred]

@csleaver @oldjeep @justgary Any thoughts on this? 🙏,

On 10/19/2023 at 11:32 AM, tedshred said:

Hi all,

Can anyone provide some real world experience on how regularly engine mount bolt tension/torque should be checked and the suggested vs recommended tension/torque for my 2009 VLX Indmar Monsoon. Particularly the bolts that secure the mounts to the fibecs channels?

 

Edited October 21, 2023 by tedshred

[BillyChinookVLX]

When winterizing my 03 VLX this year, I found all 4 engine mount bolts loose, 3 of them were missing their nuts. I replaced them all with grade 8 bolts and nylock nuts. Definitely going to be checking them every winterization from here on. 

The OEM setup on mine appears to be a flat washer, lock washer, and a nut. I see lots of flat washer lock washer stacks on all kinds of stuff. Poor engineering in my opinion. The way lock washers work is by applying tension to the threads and creating a friction point on the nut edge and mating surface. If there is a flat washer in the stack, it will just spin the washer instead of holding the nut tight. Any application that requires a flat washer should have a nylock nut instead of a lock washer.  *end of rant*

[justgary]

5 minutes ago, BillyChinookVLX said:

The way lock washers work is by applying tension to the threads and creating a friction point on the nut edge and mating surface.

Since a cut washer will compress as you tighten the bolt, it applies a longitudinal preload to the threads.  In other words, the tension is along the bolt length, not rotational.  This preload keeps the threads from vibrating loose by increasing the friction on the threads.  Any rotational friction is a bonus.  I don't have a problem with stacking a cut washer on a flat washer and tightening them until the cut washer is flat.

For a star washer, I would agree that it is best to leave the flat washer off since they actually do cut into the bolt or nut head and the base material.

You could always use drilled nuts and add safety wire if your engine mount nuts are coming loose.  This is standard practice in aircraft, since everything tends to vibrate any time an engine is running.

[tedshred]

21 minutes ago, justgary said:

Since a cut washer will compress as you tighten the bolt, it applies a longitudinal preload to the threads.  In other words, the tension is along the bolt length, not rotational.  This preload keeps the threads from vibrating loose by increasing the friction on the threads.  Any rotational friction is a bonus.  I don't have a problem with stacking a cut washer on a flat washer and tightening them until the cut washer is flat.

For a star washer, I would agree that it is best to leave the flat washer off since they actually do cut into the bolt or nut head and the base material.

You could always use drilled nuts and add safety wire if your engine mount nuts are coming loose.  This is standard practice in aircraft, since everything tends to vibrate any time an engine is running.

Thanks @BillyChinookVLX and @justgary. The current (original) setup on mine (U.S. delivery '09) is SS bolts with a single flat washer under a single brass nyloc nut. Nylon hardens over time especially when subject to heat/high temp. Hence, I would never recommend the use of nyloc nuts in engine bays. My concern with using a star washer is the galling in the surface of the Fibecs stringers. I think I'll add spring/cut washers on top of flat washers.  I guess the best option would be to line up with an annual or 50hrs check. What about torque adherence?

[oldjeep]

On 10/18/2023 at 6:32 PM, tedshred said:

Hi all,

Can anyone provide some real world experience on how regularly engine mount bolt tension/torque should be checked and the suggested vs recommended tension/torque for my 2009 VLX Indmar Monsoon. Particularly the bolts that secure the mounts to the fibecs channels?

Mine is a 2012.  Maybe I should check them some day;)

[Steve B.]

Welp, as soon as it stops raining I'm checking mine too.

[csleaver]

The Indmar scheduled maintenance chart from 2008-2009 recommends checking the shaft alignment every 300 hours or annually, so checking the engine mount hardware at the same time seems reasonable.  There is a 7/16-20 nut and flat washer on each of the trunnion pins (aka pinch bolts) for the engine stanchion mount.  The Malibu Powertrain Essentials guide recommends using blue tread lock on the nuts.  There isn't a printed torque specification that I could find, and there isn't much room for a torque wrench, but I normally get them snug at what I would guess to be at about 25 lbs/ft.  I've seen factory guys use a 3/8 air ratchet to tighten them, and mine tops out at about 35 lbs/ft. 

The engine mount top jam nut and external tooth star lock washer also doesn't have a printed torque specification that I could find, and they can be difficult to access with a torque wrench.  I get them about as tight as I can by hand with a 12" wrench which is probably around 35-45 lbs/ft.

[wakesonthesnake]

Agreed that a spindle nut and pin or wire is best but if there is room a double nut works well against vibration.  You do not have to worry about overtightening then.

[tedshred]

1 hour ago, wakesonthesnake said:

Agreed that a spindle nut and pin or wire is best but if there is room a double nut works well against vibration.  You do not have to worry about overtightening then.

The issue is access to the underside required to lock one nut against the other. However it might be sorted by inverting/flipping the bolts.

[tedshred]

Found it!

Check out these Torque values I found in the 5.7L service manual 

Edited October 22, 2023 by tedshred

[justgary]

5 hours ago, tedshred said:

Found it!

Check out these Torque values I found in the 5.7L service manual 

[Woodski]

A bolt torque chart is also a good reference guide, several options via Google search or grab a Marks handbook.

[BillyChinookVLX]

15 hours ago, tedshred said:

Thanks @BillyChinookVLX and @justgary. The current (original) setup on mine (U.S. delivery '09) is SS bolts with a single flat washer under a single brass nyloc nut. Nylon hardens over time especially when subject to heat/high temp. Hence, I would never recommend the use of nyloc nuts in engine bays. My concern with using a star washer is the galling in the surface of the Fibecs stringers. I think I'll add spring/cut washers on top of flat washers.  I guess the best option would be to line up with an annual or 50hrs check. What about torque adherence?

Valid concern with nylocks and heat. Given the position of the nuts in the engine bay, below the engine and inside the stringers, I don’t think there will be enough heat transfer to be a concern in degrading the nylon much faster than it would being somewhere in the sunlight.
 

I’m no engineer, that’s just my thought process. I have spent a fair amount of time turning wrenches on farm equipment and have seen lots of split lock washers stacked with flat washers “fail” under vibration allowing nuts to back off. Not very often have I run into Nylocks (that haven’t been used 20 times) failing under vibration conditions. I have noticed split lock washers seem to hold better with fine thread hardware compared to course thread for what that is worth.

[tedshred]

5 hours ago, justgary said:

Thanks @justgary I couldn't seem to post an image. URL was the only option. Not sure why.

[justgary]

10 hours ago, tedshred said:

Thanks @justgary I couldn't seem to post an image. URL was the only option. Not sure why.

I posted with a URL also, but I moved your image from Google, who has no concept of sharing an image in a web page.  I used Imgur, but the catch is that you have to add ".jpg" To the link.

[tedshred]

44 minutes ago, justgary said:

I posted with a URL also, but I moved your image from Google, who has no concept of sharing an image in a web page.  I used Imgur, but the catch is that you have to add ".jpg" To the link.

Ah ok. For future reference. Thank you.

[oldjeep]

On 10/21/2023 at 7:54 PM, oldjeep said:

Mine is a 2012.  Maybe I should check them some day;)

Checked them today while winterizing.  Both top nuts could be rocked, star washer keeping them from spinning.  Will deal with it in spring, it was 28f today when I went for the supplies.  Boating season is over.

 

[tedshred]

1 hour ago, oldjeep said:

Checked them today while winterizing.  Both top nuts could be rocked, star washer keeping them from spinning.  Will deal with it in spring, it was 28f today when I went for the supplies.  Boating season is over.

 

@oldjeep I am assuming you mean the top nuts were not at the spec'd tension?

[oldjeep]

13 minutes ago, tedshred said:

@oldjeep I am assuming you mean the top nuts were not at the spec'd tension?

No tension.  Only thing keeping me from spinning them off with my fingers was that the washer has dug in a little, so I could 9nly spin them back and forth a tiny bit.

[tedshred]

9 minutes ago, oldjeep said:

No tension.  Only thing keeping me from spinning them off with my fingers was that the washer has dug in a little, so I could 9nly spin them back and forth a tiny bit.

Indeed! A task for the "To do in Spring" list! What about the mount bracket to frame bolts?

[Woodski]

Loose bolts / nuts & pic of a motorcycle I assumed I was on a H-D forum 😂😱

[oldjeep]

5 minutes ago, Woodski said:

Loose bolts / nuts & pic of a motorcycle I assumed I was on a H-D forum 😂😱

Except that it isn't loud, doesn't leak oil and goes 0-60 in under 3 seconds.