nuts on engine feet

[BabaYaga]

After 18 years I am replacing the engine feet on my 20 hp Beta engine.
The original feet were made by Trelleborg, the replacements (bought from a Beta representative) are by AMC Mecanocaucho and slightly higher.
As can be seen in the photo, in my installation there is very little thread left on the height adjuster pin under the adjustment nut, in other words the engine bracket sits very low on the pin.
The replacement foot (to the right in the photo for comparison) has nyloc nuts both for height adjustment and for locking (so on both sides of the engine bracket), unlike the original, that has a nyloc nut only on the upper side of the bracket, for locking.
In order to be able to use the replacement feet, I am thinking of doing away with the lower, height adjusting nyloc nut, replacing it with a thinner, plain nut, similar the the one that is used to lock the pin to the anti vibration unit. The thread on the pin is M16 and a low profile nut would be 7-8mm thick.
Does anyone see any problem with this approach?
TIA

 

[rogerthebodger]

No need to nylock nuts in the height adjustment under the engine mounting. I have recently refitted an engine with similar M16 mountings and only have a nyloc nut on the top of the engine mounting.

I would use a thin nut to lock the M16 stud to the rubber mounting and a thin nut above to help engine height adjustment

Nyloc on to to lock it all togethr

 

[Tranona]

The engine beds are too high for the recommended mount heights. See the installation instructions pages 19 and 20.
betamarine.co.uk/resources/Operators_Manuals/10-115T-HE-OM/#page=21

However the instructions do say to mount as low as possible on the stud so the question is really about the security of the new nut compared with the nyloc. It looks like there may be little clearance between the 2 nuts, rather like the existing mounts. Are the spacings of the holes on the lower plates the same?

 

[penfold]

The engine beds are too high for the recommended mount heights. See the installation instructions pages 19 and 20.
betamarine.co.uk/resources/Operators_Manuals/10-115T-HE-OM/#page=21

However the instructions do say to mount as low as possible on the stud so the question is really about the security of the new nut compared with the nyloc. It looks like there may be little clearance between the 2 nuts, rather like the existing mounts. Are the spacings of the holes on the lower plates the same?

What he said. I'd adjust the height of the box section, or make new lower box sections from plate.

 

[wingcommander]

Ile wager originally the feet were a similar height. Your 18 years of squishing has done that. These are off my Bukh 24 , exactly the same make and firmness rating

 

[doug748]

I can't see any problem with your locknut idea, the engine is very light and not hugely powerful. If the thread and foot spacing presents further difficulties I might consider exchanging those feet.

I fitted some a couple of years ago, the feet supplied by Beta are unchanged in spec, but the Trelleborg part number has gone from RA 60 to something like RA70.....
Your local agent may have given you what he has but the original feet are out there and Beta can supply them.

.

 

[Alex_Blackwood]

Ile wager originally the feet were a similar height. Your 18 years of squishing has done that. These are off my Bukh 24 , exactly the same make and firmness rating

+1 for that. With the wear shown in the OPs photo I think I would check alignment as well!

 

[Tranona]

+1 for that. With the wear shown in the OPs photo I think I would check alignment as well!

That would suggest 15mm or so (looking at the photos) drop in height of the engine relative to the shaft and stern tube. I think there would be noisy sounds from that amount of misalignment if all feet were the same.

 

[Alex_Blackwood]

That would suggest 15mm or so (looking at the photos) drop in height of the engine relative to the shaft and stern tube. I think there would be noisy sounds from that amount of misalignment if all feet were the same.

There may be! I bet they are all a bit "Wobbly" after 18 years

 

[wingcommander]

They don't fail at the same rate either. This was my forward port foot, surveyor had pointed out surface corrosion ( from raw water pump weep) . Suggested changing . The rear portside is the previous picture, by far the worst . Obviously all four were swapped out .

 

[Stemar]

No need to nylock nuts in the height adjustment under the engine mounting.

Not sure about that. I had a nut on a VP2003 come undone and ended up with a bent prop shaft. It had been fine for over 10 years, then, for no apparent reason, it wasn't. I reckon nylock or similar is a good idea if you've got the space.

 

[LittleSister]

Not sure about that. I had a nut on a VP2003 come undone and ended up with a bent prop shaft. It had been fine for over 10 years, then, for no apparent reason, it wasn't. I reckon nylock or similar is a good idea if you've got the space.

Would a high-strength thread lock (Loctite Red?) suffice, perhaps?

Alternatively, file or machine down a full nut (on nuts), or place a sequence of washers, to make a spacer of the required depth that bears on the lower nut/mount, rather than the thread?

 

[Lightwave395]

I had a similar problem when replacing my 3YM30 Yanmar engine mounts, went with half nuts and it's been fine for past 3 years

 

[scottie]

The change in part number look very similar to rubber hardness and it is not uncommon to have different hardness front and rear depending on engine weights
purely from the photos it would almost seem that the box section is not required???????

 

[IanCC]

After 18 years I am replacing the engine feet on my 20 hp Beta engine.
The original feet were made by Trelleborg, the replacements (bought from a Beta representative) are by AMC Mecanocaucho and slightly higher.
As can be seen in the photo, in my installation there is very little thread left on the height adjuster pin under the adjustment nut, in other words the engine bracket sits very low on the pin.
The replacement foot (to the right in the photo for comparison) has nyloc nuts both for height adjustment and for locking (so on both sides of the engine bracket), unlike the original, that has a nyloc nut only on the upper side of the bracket, for locking.
In order to be able to use the replacement feet, I am thinking of doing away with the lower, height adjusting nyloc nut, replacing it with a thinner, plain nut, similar the the one that is used to lock the pin to the anti vibration unit. The thread on the pin is M16 and a low profile nut would be 7-8mm thick.
Does anyone see any problem with this approach?
TIA

View attachment 167410

Whatever you do, they are nuts to keep an eye on. Monthly checks for me, particularly the ones underneath which seem to be the ones that slack off. Torque properly and a little dob of white paint across the nut and adjoining so can easily see movement is my pennyworth.

 

[BabaYaga]

Thanks all for your replies so far.
A few comments:
I agree that the stainless steel box section used to raise the engine beds ideally could have been a bit lower than the present 50mm, but this is what I could find at the time of installation (from the scrap yard, at a very reasonable cost). So I measured carefully and found that I would have a mm or two between the two nuts. Which proved to be correct. The engine is indeed mounted 'as low as possible' on the stud, as per the installation instructions linked in post #3.
The replacement foot is almost identical to the original (hole spacing etc), but when I compare them the replacement is about 4mm higher. (Looks like more in the photo). That said, when measuring the original is 18 years old and loaded by the engine weight while the replacement is new and unloaded. So maybe the difference is smaller in practice.
I do not think the engine is seriously out of alignment, I have checked it a few times over the years and there are no such symptoms. Also, my prop shaft is very short, so the tolerance for misalignment is small. I will certainly check the alignment again after installing the replacement feet.
My two main concerns are 1) has current thinking changed so that a nyloc nut for height adjustment is now considered necessary? From the replies this does not seem to be the case. 2) will a thinner (7-8mm) adjustment nut be sufficient? Probably, as I read the replies.
Another question is should the adjustment nut be loctited? I'm not too keen on that... shim/washer below the nut might be better I think.
One advantage of having the engine bracket mounted very low on the stud is that if that nut works loose, the engine will only sink a mm or two.

 

[Pye_End]

Thanks all for your replies so far.
A few comments:
I agree that the stainless steel box section used to raise the engine beds ideally could have been a bit lower than the present 50mm, but this is what I could find at the time of installation (from the scrap yard, at a very reasonable cost). So I measured carefully and found that I would have a mm or two between the two nuts. Which proved to be correct. The engine is indeed mounted 'as low as possible' on the stud, as per the installation instructions linked in post #3.
The replacement foot is almost identical to the original (hole spacing etc), but when I compare them the replacement is about 4mm higher. (Looks like more in the photo). That said, when measuring the original is 18 years old and loaded by the engine weight while the replacement is new and unloaded. So maybe the difference is smaller in practice.
I do not think the engine is seriously out of alignment, I have checked it a few times over the years and there are no such symptoms. Also, my prop shaft is very short, so the tolerance for misalignment is small. I will certainly check the alignment again after installing the replacement feet.
My two main concerns are 1) has current thinking changed so that a nyloc nut for height adjustment is now considered necessary? From the replies this does not seem to be the case. 2) will a thinner (7-8mm) adjustment nut be sufficient? Probably, as I read the replies.
Another question is should the adjustment nut be loctited? I'm not to keen on that... shim/washer below the nut might be better I think.
One advantage of having the engine bracket mounted very low on the stud is that if that nut works loose, the engine will only sink a mm or two.

Doing the same as you this winter - got a set of Beta mounts a couple of weeks ago and they do not have nylocs as adjustment nuts. Bottom nut width 12mm. Not much less than the nyloc at the top.

The adjustment nuts on mine aren't loctited. Hasn't been a problem so far.

The drawings in the back of the manual show max and min heights on the stem rather than the text comment that it needs to be a low as possible.

 

[Alex_Blackwood]

Thanks all for your replies so far.
A few comments:
I agree that the stainless steel box section used to raise the engine beds ideally could have been a bit lower than the present 50mm, but this is what I could find at the time of installation (from the scrap yard, at a very reasonable cost). So I measured carefully and found that I would have a mm or two between the two nuts. Which proved to be correct. The engine is indeed mounted 'as low as possible' on the stud, as per the installation instructions linked in post #3.
The replacement foot is almost identical to the original (hole spacing etc), but when I compare them the replacement is about 4mm higher. (Looks like more in the photo). That said, when measuring the original is 18 years old and loaded by the engine weight while the replacement is new and unloaded. So maybe the difference is smaller in practice.
I do not think the engine is seriously out of alignment, I have checked it a few times over the years and there are no such symptoms. Also, my prop shaft is very short, so the tolerance for misalignment is small. I will certainly check the alignment again after installing the replacement feet.
My two main concerns are 1) has current thinking changed so that a nyloc nut for height adjustment is now considered necessary? From the replies this does not seem to be the case. 2) will a thinner (7-8mm) adjustment nut be sufficient? Probably, as I read the replies.
Another question is should the adjustment nut be loctited? I'm not to keen on that... shim/washer below the nut might be better I think.
One advantage of having the engine bracket mounted very low on the stud is that if that nut works loose, the engine will only sink a mm or two.

Remember it will compress a bit with engine weight on!

 

[B27]

Other solutions might include getting an aerotite nut machined down to fit, a thin nut drilled and lock wired, getting some sort of bespoke nut made with some sort of locking fixture.
If you used an upmarket washer like Schnorr above the nut, and tighten the nuts above the feet properly, I doubt it will come undone.
Do you have good access to torque the top nuts properly? M16 is going to want more than a toy spanner.
It's mostly the tension from the nut above the foot which stops the nut under the foot from rattling loose.

 

[BabaYaga]

Do you have good access to torque the top nuts properly? M16 is going to want more than a toy spanner.
It's mostly the tension from the nut above the foot which stops the nut under the foot from rattling loose.

Yes, pretty good access.
There is also a split washer that I suppose will help to provide torque.