Engine Mount Hold Down Bolts

[Winf]

Hi all

Need to replace the engine mounts on our Yanmar 3HM30. Total engine weight is approx. 160kg

Going with Isoflex engine mount units. Will need to do them one at a time then do engine/shaft realignment.

Existing bolts holding engine mount to the stringer are 2 x 8mm x 75mm bronze hanger style with a stainless nut and oversize flat/spring washer.

Hold down bolt hole size in the old mounts (and the new mounts) will fit a 12mm bolt.

At least one of the hold down bolts was not solidly locked into the stringer - suspect maybe some water intrusion and possibly some rot in there - but the bronze bolts are still A1 condition.

So:

Do i reuse the bronze bolts and fix them into the stringer with epoxy? I like this option due to the use of bronze but would prefer the size to be increased to 12mm - can't locate any of these bronze bolts in Oz.

If i go with stainless 12mm, do I epoxy them in or not?

Thanks

Winf

[coopec43]

Would it be wrong to use M12 316 SS?

I wonder if you are looking for the right type of bolt? I think you better get expert opinion because I am no expert.

What is cupro nickel used for?
Copper-nickel (also known as cupronickel) alloys are widely used for marine applications due to their excellent resistance to seawater corrosion, low macrofouling rates, and good fabricability.

https://www.copper.org/applications/marine/cuni/

[coopec43]

I did a search on "Silicon Bronze" and got quite a few Australian links.



FASTENERS 101™
Fastener Grades, Strength & Materials

https://www.albanycountyfasteners.co...als-s/1129.htm

[Wotname]

Winf, I would be very surprised if you can source bronze hanger bolts in Australia. I tried recently and gave up after many phone calls, emails and google searches. I could get them in the USA but the freight was killer.

You can source bronze lag bolts (coach screws) from a few places in Australia and most people suggested to simply cut the head of a suitable lag bolts and tap the required thread onto the shank.

Presumably you would use bronze nuts.

[oleman]

Mastercarr.com has bronze SAE bolts in all popular sizes and lengths. A casual search of their website did not find any metric bronze bolts. Mcmastercarr ships world wide. Great old company out of Chicago Il but moved to Atalanta Ga years ago. Never purchased anything from them to be shipped out of the USA but they are probably the best hardware provider in the US. Their website tells it all and a great technical resource.
7/16" bolts would be 11.1125 MM.
I would use silicon bronze in every bolt position where it is strong enough. Actually I use SB bolts on all water related connections and the exhaust connections on the diesel.

[sailingchiro]

For soft decks and engine mounts, I use Git-Rot because it will "soak"into the old soft wood and make it solid. Right or wrong, it is the way for me. It can be found on-line for $50/quart or West Marine for $89/quart. Easy to mix and let is soak into the stringer. I keep filling it until there is pressure (deck with syringes) or topped off at the stringer. It soaks up quite a bit, more than you would expect especially into dry balsa core. Dries overnight then redrill to the size you need.
In fact, I found a bolt loose last time out and will need to do next week.

Experts out there, I know you would never do this. But I am not an expert. I know nothing!!!!

[Stu Jackson]

Why not use lag bolts?

[a64pilot]

I don’t like lag boats because they can allow water intrusion, even if they are installed with 5200 or similar.
I like the idea of using lag bolts with the head cut off and threaded to make them into studs, they can be permanently bedded in with epoxy.
Wotname’s method

[coopec43]

Like Wotname says you can't buy hanger bolts in Australia.

I think this listing of suppliers may all be in the US of A (but they may have outlets in Australia?). Of course the cost of having anything posted from the US is hideous.

Hanger Bolts Suppliers

Displaying 1 to 25 out of 175 suppliers
Search Within

https://www.thomasnet.com/products/h...6551204-1.html

[Reefmagnet]

I'd use coach bolts and butyl or even lanolin grease as the sealant. It's a pain in the neck lifting a mount over projecting studs if it's a squeezy fit. If the woods rotted it must be from fresh water? Not that 316 coach bolts are hard to come buy, but I'd probably favour hot dipped galvanised simply because they will reveal their condition more honestly as time progresses and, let's face it, the engine manufacturers and marinisers don't exactly splurge on exotic materials.


Another option is to install a plate that overlaps the rot area so it bolts to solid wood and then screw studs or bolts into tapped holes in it.

[Alan Mighty]

Originally Posted by Wotname

I would be very surprised if you can source bronze hanger bolts in Australia. I tried recently and gave up after many phone calls, emails and google searches.

Yair. You may not be able to get "bronze hanger bolts" in Aus. But you can buy such fastenings off the shelf in 304 stainless steel. And some other materials.

Just that they're not always called "hanger bolts". That name is a little bizarre. The wise head who idles on the dock at the marina reckons that name started in the railway car building business in the US in the early 20th century, for bolts used to mount the "brake hanger carrier".

In Aus, you're more likely to find such a bolt - with a lag screw or wood screw thread on one end and a machine thread on the other - under name such as "stair bolt", "wood screw stud", "dowel screw", or "dual thread lag screw". Of course, sometimes "hanger bolt" will be used.

See, for interest: https://www.allfasteners.com.au/dual...tainless-steel

[coopec43]

You are on the ball Alan!


Hanger Bolts manufacturers|Dowel Screws suppliers in india at best price

TorqBolt

Hanger bolts are also known as: couch bolts, headless hanger bolts, and hanger screws. Being headless, a little ingenuity is needed to drive them into wood.

https://www.torqboltinc.com/steel-fa...manufacturers/


I did a search on "threaded screw" and came up with this.

https://www.google.com.au/search?q=t...P0SU5tdF0E7sM:


https://www.theoutdoorshop.com.au/Du...tainless-Steel

[Wotname]

To be clear, in Oz, you can get hanger bolts (insert favourite name here) in a variety of materials but not in silicon bronze.

Freight from the USA was quoted at $75 USD - ouch! Probably could have found a cheaper freight option but didn't pursue it.

[Alan Mighty]

Originally Posted by Wotname

To be clear, in Oz, you can get hanger bolts (insert favourite name here) in a variety of materials but not in silicon bronze.

Of course, an enterprising young lass might instead buy:

* threaded silicon bronze rod (see: https://shop.classic-boat-supplies.c...c-thread-90cm/) and cut the lag screw thread; or

* plain silicon bronze rod (see: https://shop.classic-boat-supplies.c...od-plain-90cm/) and cut both threads.

[GordMay]

Silicon Bronze fasteners (‘Everdur’ are one brand) are often used (North America) on electrical pole line hardware. Perhaps an electrical distributor could help you source them, even in Australia.
If Australians don't use silicon bronze in this application, I would expect their preferred material to likely be an adequate substitute.