Transom bolts - what kind to use?

[medicineman]

I have read the threads on here but am confused.

No Zinc plated bolts on transoms? What kind of bolts will not react with aluminum transom? SS 316 and a dab of 3M 5200?

 

[Axhammer]

Yup, SS bolts & 5200 sealant.

 

[Crazyboat]

When I beefed up my transom as a kid, we first used whatever we had laying around. As a kid all you want is to be on the water, all else be damned. 2 years later when the bolts were showing obvious signs of rust, we swapped them out for SS bolts and whatever kind of sealant there was in the late 70's.

 

[airshot]

Take a magnet when you buy your bolts, if it attracts don't use them.

 

[jethro]

If you use your boat in the salt, stainless will still cause galvanic corrosion. It may not be an issue with freshwater, but I have all stainless fasteners on the bow of my boat and 20 years of striper fishing has caused a whole bunch of galvanic corrosion. See this link: https://www.albanycountyfasteners.com/blog/stainless-steel-and-aluminum/

This is why structural aluminum rivets are the way to go.

 

[thill]

Yes, 316 stainless and sealant. Not 304 or 308, but 316. It will be non-magnetic as mentioned above.

 

[jethro]

Why do I even try.

 

[LDUBS]

Why do I even try.

For some reason I thought we were talking about bolts used to mount the outboard. Now I think I was jumping to the wrong conclusion.

 

[airshot]

If you use your boat in the salt, stainless will still cause galvanic corrosion. It may not be an issue with freshwater, but I have all stainless fasteners on the bow of my boat and 20 years of striper fishing has caused a whole bunch of galvanic corrosion. See this link: https://www.albanycountyfasteners.com/blog/stainless-steel-and-aluminum/

This is why structural aluminum rivets are the way to go.

The salt itself will react to the aluminum over time, so you still loose.

 

[LaqueRatt]

You know, I'm sure you guys are right about all these chemical reactions and how vulnerable the alum is to deterioration when certain materials are in contact with it. Maybe because I'm 1,000 miles away from the salt, but I'm not seeing any of this. Even though I've had tinnies that had regular nuts and screws and treated lumber as well. In fact, virtually every piece of hardware I'm seeing that has been added by someone is just normal crap and yes, it eventually rusts, but not for quite a while. Not to be contrary, but I'm thinking it would take years for this to be an issue. Am I wrong?

 

[medicineman]

Thanks all. Here in MN heard a lot about corrosion from treated lumber, zinc hardware, etc.

I am going to try to rivet the transom with 1" grip rivets, and will be sealing the wood with Steelflex (in addition to painting the whole boat, every inch, with Steelflex). May put 5200 to lock the transom in, too.

No treated lumber either, sealing the ply with Steelflex then riveting that down too.

Will share pics... About $1k in on the project so far.

 

[Tin Man]

OP...please provide additional details....salt or fresh water, engine mounting bolts?

If salt...beware...salt, alum, and SS = corrosion.

If motor mounting bolts:

If fresh, SS 316 is good. OEM bolts are typically 1/2" fine thread (or metric equivalent) with nylocs.

 

[Crazyboat]

You know, I'm sure you guys are right about all these chemical reactions and how vulnerable the alum is to deterioration when certain materials are in contact with it. Maybe because I'm 1,000 miles away from the salt, but I'm not seeing any of this. Even though I've had tinnies that had regular nuts and screws and treated lumber as well. In fact, virtually every piece of hardware I'm seeing that has been added by someone is just normal crap and yes, it eventually rusts, but not for quite a while. Not to be contrary, but I'm thinking it would take years for this to be an issue. Am I wrong?

What do you mean by years? 1-2 years or 10-20 years? I would not want to leave a tin boat in the salt day and night untreated for a few years straight. When I had my tin, it was all of 80 pounds and I took the engine off every Sunday and pulled the boat up onto the dock. Next Friday it went back in for 48 hours or so. After a few years 2-3) you could see light damage. Bear in mind this was a cheaper Sears 12' tin, was build pretty poorly as tin boats go.

 

[LDUBS]

You know, I'm sure you guys are right about all these chemical reactions and how vulnerable the alum is to deterioration when certain materials are in contact with it. Maybe because I'm 1,000 miles away from the salt, but I'm not seeing any of this. Even though I've had tinnies that had regular nuts and screws and treated lumber as well. In fact, virtually every piece of hardware I'm seeing that has been added by someone is just normal crap and yes, it eventually rusts, but not for quite a while. Not to be contrary, but I'm thinking it would take years for this to be an issue. Am I wrong?

I guess my perspective is to use the best practice to avoid corrosion down the road. Hopefully I'll still be using it years down the road. If not, maybe the next guy will say something nice about the previous owner taking care of the boat.

 

[airshot]

Certain metals like brass react with aluminum quickly, like a year or two and it will corrode right thru. Good SS and alum will take near a life time. Even steel on alum will take longer than most folks keep their boat..
Treated lumber has changed the chemicals used a couple decades back. The warly stuff was really vad for aluminum, but the newer chemicals are so weak, it takes a long time to react to aluminum! In fact todays treated lumber is pretty useless on the ground or even outside. Most all the treated lumber today doesn't last much longer than regular lumber...I would no longer fear using todays treated lumber on aluminum. I have some alum trim attached to treated lumber for almost 20 yrs on my home, no sign of corrosion and the treated wood is worse off than the regular boards. Todays treated lumber means you just pay more for nothing...

 

[airshot]

You know, I'm sure you guys are right about all these chemical reactions and how vulnerable the alum is to deterioration when certain materials are in contact with it. Maybe because I'm 1,000 miles away from the salt, but I'm not seeing any of this. Even though I've had tinnies that had regular nuts and screws and treated lumber as well. In fact, virtually every piece of hardware I'm seeing that has been added by someone is just normal crap and yes, it eventually rusts, but not for quite a while. Not to be contrary, but I'm thinking it would take years for this to be an issue. Am I wrong?

Steel is relatively slow, but things like brass and copper corrode really fast ! In my youth I mounted a bow light with brass screws on an aluminum deck, in just one year, the bolts ate away the aluminum and pulled thru, the bow light came back and slammed me in the head while running up the river !! Learned my lesson!!!