# Question for gurus on a large hinge bolt on a saltwater trailer



## Backwater (Dec 14, 2014)

Ok, like the drilling 1/4" steel thread I just posted, I have another post for opinions on a large bold I need for a hinge bolt on a galvanize trailer project I'm re-doing for use in saltwater.

This trailer is to be used for a light skiff (think Wingmaster Sandpiper 15, only it's 17ft with a 30hp OB) in rough conditions. The reason I went with this used trailer is it tilts and I need that for some of the shallow sand and gravel ramps I will be using, off the side of the road (not to mention ramps that are just spots where I push the trailer thru some weeds, ledges, oysters, rocks and crap, tilt the trailer and drop it over the side). So it's very non-conventional launching in spots where ramps just don't exist.

It's a galvanized steel trailer that I'm re-finishing to be more durable and corrosion resistant. So it tilts by the frame and main tongue beam hinging or pivoting on one single 5/8" bolt. The tongue beam is basically 3" x 2" rectangle steel tubing (1/4" steel) and the trailer frame has basically 2 - 1/4" thick bar side plates, mounted such so the steel tubing tongue goes in between the 2 side plates (with 5/8" holes) and gets 1 bolt thru them (5/8" bolt with about a 2 3/4"" solid shank on a 4" long bolt). Basically, the outside width of the 2 plates are 2 3/4" and the bolt will get a washer, lock washer and nut. So everything past the tongue beam on that trailer hinges on that 1 bolt. When I first took it off, I think it was a zinc coated bolt that rusted badly where I couldn't get the nut off and it had to be cut off. Not sure if it was a regular grade 5 or grade 8 bolt.

So here's the question. I'm imagining the 1/4" steel will wear thru any finish on any bolt, except thru stainless steel (since they are made solid SS). I am wondering if I went to an all hot dipped galvanized bolt (they are made with normal grade 5 steel, like normal zinc plated bolts), will the finish hold up with the friction and wear, even if I add more finish to it, or will it wear thru and start to rush and therefore might cause a break. Also, will it also have enough sheer strength or do I need to go to a grade 8 bolt. And if the grade 8 bolt, will it rust out fast as normal zinc coated grade 5, even if it's treated with Corrosion X or something like that? Then I have the option of going with a stainless steel bolt. If so, being a softer metal than grade 5 (more like grade 3), will it have enough sheer strength to hold up to that, even tho it will be good to fight off rust and corrosion good?

I know I'm over thinking it and I also know I can change out that bolt periodically, but looking for more of a permanent solution.

What's your thoughts or experience?

Ted


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## firecat1981 (Nov 27, 2007)

Holy cow man, you are over thinking this. I have a tilt trailer and can tell you the hinge point will never be submerged, as long as you rinse the trailer after each dip and grease the bolt on occasion a galvanized bolt will last a long time, like decades.

On a side note, try to condense your thoughts a bit, not trying to stop you from posting, but many times if a post is long for a simple purpose people will lose interest before finishing and you won't get many answers.


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## LowHydrogen (Dec 31, 2015)

Tensile strength and toughness are two different things, gr8 is high in tensile strength but brittle, it doesn't do well with vibration or shock loading. 
Toughness is a metals ability to absorb energy (deform) and retain strength without breaking.

I would go with stainless. It has lower tensile priorities but incredible toughness. Make sure to use Never-sieze on the threads because they're prone to galling.

jmho good luck


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## Backwater (Dec 14, 2014)

firecat1981 said:


> Holy cow man, you are over thinking this. I have a tilt trailer and can tell you the hinge point will never be submerged, as long as you rinse the trailer after each dip and grease the bolt on occasion a galvanized bolt will last a long time, like decades.
> 
> On a side note, try to condense your thoughts a bit, not trying to stop you from posting, but many times if a post is long for a simple purpose people will lose interest before finishing and you won't get many answers.


I know it wouldn't be submerged. But the boat will drip on it and there may be times where I can't wash it on long trips.

YEa I will try to get more concise on the subjects!  Thanks!


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## Backwater (Dec 14, 2014)

LowHydrogen said:


> Tensile strength and toughness are two different things, gr8 is high in tensile strength but brittle, it doesn't do well with vibration or shock loading.
> Toughness is a metals ability to absorb energy (deform) and retain strength without breaking.
> 
> I would go with stainless. It has lower tensile priorities but incredible toughness. Make sure to use Never-sieze on the threads because they're prone to galling.
> ...


I was thinking sheer strenght when I thought of gr8, but never thot it wouldn't hold up to vibration. Never considered toughness as you described, but it makes sense. But I figured a galv bolt would be tougher than a SS bolt. But then I can see it holding up to corrosion and rust better and it absorbing impact and bending before it breaks. But worried about sheering off, due to getting banged around. I figured that 1 bolt suffers the most pounding than any other thing on the trailer.


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## Jason Cooper (Dec 6, 2016)

Hitch pin and done.


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## MooreMiller (Sep 10, 2016)

I believe the shear strength of a grade 5 5/8" bolt is around 20,000 lbs. I wouldn't worry about that. 

I've pulled galvanized bolts off trailers that started to rust because the zinc coating had been eaten through just by torquing down the bolt against the trailer. I don't feel hot dipped galvanize is a very durable coating. 

I think the galvanized bolts you buy at the hardware store have a thinner zinc coating than what you would find at the boat trailer parts store. I would love to hear some incite on this.


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## LowHydrogen (Dec 31, 2015)

Backwater said:


> I was thinking sheer strenght when I thought of gr8, but never thot it wouldn't hold up to vibration. Never considered toughness as you described, but it makes sense. But I figured a galv bolt would be tougher than a SS bolt. But then I can see it holding up to corrosion and rust better and it absorbing impact and bending before it breaks. But worried about sheering off, due to getting banged around. I figured that 1 bolt suffers the most pounding than any other thing on the trailer.


Can you put a pic up? I'm having trouble picturing the bolt location. I have a tilt trailer under my 13' hawk. Is it in the same location here, but just through bolted?
View attachment 6667


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## Backwater (Dec 14, 2014)

I copies these pics from one of the most well know members on this site, Brett!

http://www.microskiff.com/threads/boat-trailer-modification.3028/



















Of course, this is not my trailer, but it is a simular action, except it doesn't have the front locking pin, just the top latch, like you have there. Btw, notice the rust on your latch pin. I'm sure you don't dunk that under water when you launch. Still, it rusted. Maybe from the dripping boat over it.


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## LowHydrogen (Dec 31, 2015)

I'm certain SS would be fine in that location. A lot of the stress is distributed along the tongue. Also most everything is designed with a 3:1 safety factor. SS is more than 1/3 the strength of steel if you wanted to think of it that way.

Honestly I don't think the pin was ever galvanized on my trailer. Trailer is just in really good shape for its age. Born in April of 84!!! It doesn't see much salt water but when it does I back the whole thing in the lake by my house.


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## DuckNut (Apr 3, 2009)

Backwater said:


> Of course, this is not my trailer, but it is a simular action, except it doesn't have the front locking pin, just the top latch, like you have there. Btw, notice the rust on your latch pin. I'm sure you don't dunk that under water when you launch. Still, it rusted. Maybe from the dripping boat over it.


Ted, Make the trailer resemble the pics with a spring loaded latch up front.

The latch pin WILL rust no matter what you do because they are not a treated steel, just steel.

But you also need to understand that the boat has to be on the trailer far enough forward so that when you pull the latch you don't get knocked out and when you are loading the trailer comes down and latches by itself. If you set it up for dry launch, you will grow aggravated real quick and often.


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