Engine mount studs (M16) - What to use? Anything special?

[dankilb]

Seems like you really want to make things though!

Yes! …but, I need to make spacer blocks anyway (not sure that’s the correct term, but the space between the bearers and the AV mounts is maybe 20mm).

Following Moodysailors’s inspiration, my point is that - if I get the blocks the right sort of height - the only adjustability I need might be a washer or two.

Watched one of the old boys in the yard aligning the hard mounted lump on his ex- commercial shrimper the other day using only shims and went from ‘how do you do that??’ to ‘doesn’t look too hard!’ having seen it.

Off to the boat today so I’ll have another look and measure.

I need the mounts I have either way, as the old ones and most of their studs are cactus.

 

[Tamar]

I had a M16 stud fail on the Thursday before the Easter holidays a few years ago. The boat is a charter boat and everywhere was closed for the weekend. I happened to have some M16 stainless stud bar on the boat, cut down to fit, fast forward 3 years and it is still in situ. I ordered 4 spare which are still in the spare locker. Sometimes these studs are inferior quality.

 

[CassoIoW]

Just received four smart new engine mounts from the helpful folks at AV Industrial (who I think manufacture themselves and advised on the right model for our Beta 50):

Question is, what do I stud them with (M16)? Is regular (mild) threaded rod okay? Do I need HT/8.8? And I'm assuming (hoping?!) stainless not required/worth it?

TIA

No problem using studding but whatever you use I would reccomend using stainless. Your using them in the marine environment so anything that avoids corrosion is better and when you come to change them they wont be rusted up

 

[Moodysailor]

Sorry, but I really don't see what you are trying to improve. Studs are the standard way of mounting this size engine and almost universally used by engine manufacturers. my first re-engine was replacing a Stuart Turner with a Yanmar 1GM. The ST was adjusted with shims cut out of roofing lead - what a PITA. The method I described earlier was a doddle. I built a jig using a 1" broom stick for a dummy shaft down the stern tube and Ply sections to represent the mounting brackets to scale. Built up the hardwood beds to the right height and angle. Dropped the engine in connected to the shaft, lined it all up and bored the pilot holes for the fastening on the mounts to the beds. Replaced that with a Nanni which a different bracket heights and spacing so dropped the engine in, connected it up with temporary spacers to get the bed height right, lifted the engine and fitted full length spacers to the beds and dropped the engine back in, drilling for the hold down fastening as before.

If you get the mounts at the right height as in your earlier diagram you have enough for fine adjustment. Lock it all up and it is idiot proof. What are you hoping to achieve over and above that with your complicated spacers and shims?

This is exactly the type of commercial pressure that lead to studs being used in this application in the first place.

Please don't misunderstand me, I agree that it's a faster way of doing it - that's the point. But studs are not the technically best solution. There is a reason why we do not use them in the commercial marine world.

 

[PetiteFleur]

I would just get the studs from the supplier and fit as before - we replaced the mounts on a friends Nanni 14hp last year as a couple of mounts had sheared, and the supplier in Norwich threw in the studs as well - which was just as well as when we eventually removed the mounts ALL the studs had sheared! And it had obviously been like this for some time... Now running nicely.

 

[Tranona]

This is exactly the type of commercial pressure that lead to studs being used in this application in the first place.

Please don't misunderstand me, I agree that it's a faster way of doing it - that's the point. But studs are not the technically best solution. There is a reason why we do not use them in the commercial marine world.

They are absolutely fine for the OPs usage. There are many products where higher specification solutions are required for more demanding applications - this is just not one of them. Fail to see anything about commercial pressures in my post and nothing unusual in the description of my method.

The downside of the OPs proposal as far as I can see is that he has to get his spacers absolutely right with the engine properly aligned before he bolts it down as he has no easy way of making adjustments without lifting the engine and fitting shims. Who wants do do that. Get the mounts at the correct height (which may need spacers depending on the height of the beds) and minimal adjustment on the studs is necessary - but it is there. Makes no difference to the performance of the mount and will last the life of the engine (or at least the mounts!).

 

[Moodysailor]

They are absolutely fine for the OPs usage. There are many products where higher specification solutions are required for more demanding applications - this is just not one of them. Fail to see anything about commercial pressures in my post and nothing unusual in the description of my method.

The downside of the OPs proposal as far as I can see is that he has to get his spacers absolutely right with the engine properly aligned before he bolts it down as he has no easy way of making adjustments without lifting the engine and fitting shims. Who wants do do that. Get the mounts at the correct height (which may need spacers depending on the height of the beds) and minimal adjustment on the studs is necessary - but it is there. Makes no difference to the performance of the mount and will last the life of the engine (or at least the mounts!).

As always, individual opinions vary. I for one have seen hundreds of mount studs snapped over my time as a marine engineer - we used to keep them on stock at our dealership as a high turnover item. There are several references to this within this thread too. So stating "fine" is subjective as my experience is not the same as yours.

Personally, I don't see it being an issue, nor particularly difficult to shim the mounts. When I started out in my first job we used to provide shim packs with bolted mounts, so you can say I cut my teeth on that method, and I know from my work in the marine industry that using studs on mounts is accepted - not preferred.

The fact that studs are quick and simple to adjust is what created the commercial pressure, it's the voice of the customer that manufacturers listen to, and if fitting studs mean they can sell more engines then they do this. You have alluded to this fact in your post. This cynic in me also says the increased spare parts sales is also a benefit

What I am saying has to be taken in the context of the OP's question - I am not suggesting that every small engine manufacturer should stop selling engines with studs on the mounts - I'd be laughed out of any office for the suggestion. What I am saying is that if I had a set of mounts with no hardware, I would go with the best possible engineering solution, not the second best. Having a set of shims cut on a waterjet, 3D printed (with the correct filament), or made from GRP or hardwood does not cost that much. It is also possible to use something like chockfast, which is used in the marine commercial world - but that is an extreme solution and overkill for this application.

There are downside to both choices. It takes a bit more time with shims, and they are more fiddly. However, I have seen plenty of engines installed badly with studs - either uneven mount loading, misaligned mount to feet and engines mounted too high.

If you speak to the mount manufacturers (Trellborg, Vulkan, et al), they will advise to place the equipment directly to the AV mount if at all possible. The reason is that these mounts have to resist load in 3 planes and when the engine is mounted higher up this has the effect of increasing the lateral loads on the mount, this can have undesirable consequences (mounts don't work within their designed range, premature failure of mount or hardware, etc). I've done some work with these on a couple of bespoke projects, and the calculations that go into the mount specification is quite detailed at this level.

 

[dankilb]

The current installation is ‘jacked up’ pretty high off the bearers, especially the aft ones (shown here - needing a clean after nearby grinding):

Specifically, I made it around 30mm for the block and about the same taken up by the stud (30mm between the AV mount and the Beta mount). So 60mm total.

I might need to find something cheaper than alu flat bar to make a thick enough block/spacer. Assuming around 50-55mm, to allow for shimming, or a bit thinner if using stud adjuster. Still undecided.

 

[earlybird]

The current installation is ‘jacked up’ pretty high off the bearers, especially the aft ones (shown here - needing a clean after nearby grinding):

Specifically, I made it around 30mm for the block and about the same taken up by the stud (30mm between the AV mount and the Beta mount). So 60mm total.

I might need to find something cheaper than alu flat bar to make a thick enough block/spacer. Assuming around 50-55mm, to allow for shimming, or a bit thinner if using stud adjuster. Still undecided.

What actually holds that wooden spacer block in position on the bearer? Does the hexagon headed fastener go all the way through or is it something else not visible in the photo?

 

[dankilb]

Having a set of shims cut on a waterjet, 3D printed (with the correct filament), or made from GRP or hardwood does not cost that much. It is also possible to use something like chockfast

This is what I’m pondering now… and iroko does seem a lot cheaper than other options, so far (various flat bar or chocking compound).

I could lay them up out of glass, but could do without the faff. I’ve kept some scrap flat Jen factory laminate I removed during the refit. That could be laminated and machined into something of the right size (and for free!).

 

[dankilb]

What actually holds that wooden spacer block in position on the bearer? Does the hexagon headed fastener go all the way through or is it something else not visible in the photo?

Yup. The two hex bolts have nuts and washers below the aluminium bearer extrusion.

The existing bolt holes don’t match the new (slightly larger) mounts anyway, so that can all be redone.

 

[BabaYaga]

I might need to find something cheaper than alu flat bar to make a thick enough block/spacer. Assuming around 50-55mm, to allow for shimming, or a bit thinner if using stud adjuster. Still undecided.

Just to throw another idea into the pot…
This photo is from my installation. Instead of a solid block of something as a spacer, I used pieces of rectangular tube, from memory 120 x 50 mm, material thickness 5 mm. Stainless steel, so would have been expensive if I hadn’t picked them from the scrap yard. Obviously mild steel would be fine if painted. Just a matter of finding the right dimensions.

 

[dankilb]

Update - the new AV mounts are 8-10mm taller (may compress a bit under load, presumably), so taking that into account I’ve priced the following for blocks:

• 45mm iroko - around £40 (plus a few £s for fasteners and washers to shim)
• 3” x 1.1/2” aluminium flat bar - at least £80 (but plenty of local scrappies to try for - hopefully - much cheaper
• 3" x 1.1/2" x 10 swg rectangular box/tube - surprisingly reasonable at <£40 (but that’s quite thin-walled, 3mm, so it’d presumably need some reinforcement inside - again, maybe local scrappy might have thicker/stronger)
• Pourable chocking compound - seems to be in region of >£80 (couldn’t gain access to make them in place, so that probably offsets the gain in ease)
• Epoxy layup - free, as I already have plenty of glass, resin and also good quality, flat, scrap polyester grp (but a fair amount of messy work)

So far, no options really stand out. I think the best bet may be to visit some scrap metal merchants for further inspiration. It’s not that I’m determined to pinch the pennies - but anything pushing £100 just to support the lump seems questionable.

The original studs question won’t help here, yet, as new spacers are needed anyway. I would struggle to run studs without much thinner spacers foreward than aft. This is off putting for me because it makes sourcing/machining material harder still.

Btw, the original motor was a Perkins ‘Prima’ M50 - current is 2012 Beta 50.

Judging from @BabaYaga’s post #32, a similar ‘lift’ is required for other Beta installations.

 

[Moodysailor]

Update - the new AV mounts are 8-10mm taller (may compress a bit under load, presumably), so taking that into account I’ve priced the following for blocks:

• 45mm iroko - around £40 (plus a few £s for fasteners and washers to shim)
• 3” x 1.1/2” aluminium flat bar - at least £80 (but plenty of local scrappies to try for - hopefully - much cheaper
• 3" x 1.1/2" x 10 swg rectangular box/tube - surprisingly reasonable at <£40 (but that’s quite thin-walled, 3mm, so it’d presumably need some reinforcement inside - again, maybe local scrappy might have thicker/stronger)
• Pourable chocking compound - seems to be in region of >£80 (couldn’t gain access to make them in place, so that probably offsets the gain in ease)
• Epoxy layup - free, as I already have plenty of glass, resin and also good quality, flat, scrap polyester grp (but a fair amount of messy work)

So far, no options really stand out. I think the best bet may be to visit some scrap metal merchants for further inspiration. It’s not that I’m determined to pinch the pennies - but anything pushing £100 just to support the lump seems questionable.

The original studs question won’t help here, yet, as new spacers are needed anyway. I would struggle to run studs without much thinner spacers foreward than aft. This is off putting for me because it makes sourcing/machining material harder still.

Btw, the original motor was a Perkins ‘Prima’ M50 - current is 2012 Beta 50.

Judging from @BabaYaga’s post #32, a similar ‘lift’ is required for other Beta installations.

I'm not sure if this will work, and it would certainly require checking with the engine manufacturer, but could you unbolt and invert the engine feet?

 

[penberth3]

I had a M16 stud fail on the Thursday before the Easter holidays a few years ago. The boat is a charter boat and everywhere was closed for the weekend. I happened to have some M16 stainless stud bar on the boat, cut down to fit, fast forward 3 years and it is still in situ. I ordered 4 spare which are still in the spare locker. Sometimes these studs are inferior quality.

I bought some threaded bar from Toolstation and the thread form was very poor. Might have been OK for an odd job but not for anything structural. Lesson learnt - go to a proper nut and bolt supplier for quality.

 

[Tamar]

I bought some threaded bar from Toolstation and the thread form was very poor. Might have been OK for an odd job but not for anything structural. Lesson learnt - go to a proper nut and bolt supplier for quality.

They are basically threaded bar with a notch on the top for a spanner, you could use a long bolt I would imagine

 

[dankilb]

So long as the fastener is of a decent quality - at M16 size it shouldn’t really matter whether stud/bolt/etc…

I just remain unconvinced by the design of the ‘adjusters’, especially the need for locking and adjusting nuts.

We do enjoy relatively good engine access and it should be easy to jack up fore/aft/port/stbd to adjust without adjusters. Plus we have a floating shaft log with no cutlass bearing, so there is no running adjustment possible once the lip seal is fitted. It’s a ‘one and done’ job - using a ‘top hat’ bearing I machined out of brass to hold the shaft centrally in the shaft log.

It’s now just a question of whether I can (or would want/need to?) use anything other than hardwood to space under the AV mounts/feet?