Bolt grade

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bke

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I have to take my motor off to mount my talon on. I need to buy longer bolts. Was just wondering what grade of bolts should I buy?
 
Bondo

Bondo

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Re: Bolt grade

Ayuh,.... Longer bolts for Where,..??

How big a motor,..??
 
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agallant80

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Re: Bolt grade

Drywall screws will work fine.... JK

The last time I was at West Marine I saw they had a collection of stainless bolts in all dementions. I would just avoid Nickle or Zink plated.
 
greenbush future

greenbush future

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Re: Bolt grade

Fastenall may be a better choice for getting your hardware once you figure out what sizes you need. I would think stainless steel would be a great choice. What is in there now?
 
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pevaguy

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Re: Bolt grade

It depends on where you boat, if in salt water, I would suggest stainless steel, if in fresh water, grade 8 nickel plated would work. For maximum strength, grade 8 fine thread. You can always use a grade 8 where a grade 2 will work, but not a grade 2 where you need a grade 8. When I had my truck repair business I only stocked grade 8 for that reason.
 
dingbat

dingbat

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Re: Bolt grade

As noted above, dry wall screws would probably work.....:lol:
The fiberglass would break and crumble long before even the softest bolt would even reach 1/4 load.
 
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bke

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Re: Bolt grade

I was thinking about getting ss bolts. I don't know what grade of bolts are holding the boat. since my boat is put away for the winter. My motor is 150 Yamaha. The boat is a fiberglass boat.
 
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Chris1956

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Re: Bolt grade

Normally SS bolts are about grade 2. If you are using four 1/2" bolts, Stainless steel is plenty strong. Fine thread with nylon locknuts and washers are a real good idea.
 
Scott Danforth

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Re: Bolt grade

I recommend flourocoated grade 8 fasteners for anything load bearing. that way you get the strength and the 2000 hour salt spray protrection. however if you can live with 1000 hour salt-spray protection, there are the ultra-coated fasteners. you can even get them delivered to your house if you order from mcmaster carr McMaster-Carr

if you want stainless, look for 17-4ph fasteners. it does have carbon and will eventually patina, however they are comparable to a grade 5
the stainless hardware from west marine and other places is either 304 or 18-8. 316L would be better, however that is not common. both the 18-8 and 304 fasteners have the strength of a grade 2.
 
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Chris1956

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Re: Bolt grade

You sweetwater types can indulge yourselves with coated steel bolts. It is much better to use Stainless Steel here on the salty coast. 4 SS 1/2" bolts are much stronger than the transom bracket of the outboard.
 
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H20Rat

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Re: Bolt grade

pevaguy said:
You can always use a grade 8 where a grade 2 will work, but not a grade 2 where you need a grade 8.
Click to expand...

No... Bolt grades aren't interchangeable. A grade 8 will require 2x to 3x as much torque to fasten it to the proper spec compared to a grade 2. The underlying material (wood) may not be able to support that much compressive force. So what you end up with is a properly fastened/torqued grade 2, or a grade 8 that isn't torqued to spec, and will work its way loose eventually. (again, not saying it will, just hypothetical, and also assuming you aren't using nylocs or loctite.)

Also, lock washers can not be used on high grade bolts, as they don't bite into the metal.

Overkill isn't always best... its better to match the material/tool to the requirements.
 
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gm280

gm280

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Re: Bolt grade

smokingcrater said:
No... Bolt grades aren't interchangeable. A grade 8 will require 2x to 3x as much torque to fasten it to the proper spec compared to a grade 2. The underlying material (wood) may not be able to support that much compressive force. So what you end up with is a properly fastened/torqued grade 2, or a grade 8 that isn't torqued to spec, and will work its way loose eventually. (again, not saying it will, just hypothetical, and also assuming you aren't using nylocs or loctite.)

Also, lock washers can not be used on high grade bolts, as they don't bite into the metal.

Overkill isn't always best... its better to match the material/tool to the requirements.
Click to expand...

Okay smokingcrater, I'll admit I am not a forensic metallurist and didn't stay at a Holiday Inn last night either, but could you explain to me exactly what you stated about torque numbers again. I honestly don't understand your thoughts. 80lbs of torque applied to a 1/2" x 20 TPI grade 2 bolt is the same as 80lbs of torque applied to a 1/2" x 20 TPI grade 8 bolt. Please explain and educate me...I'm listening.
 
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pevaguy

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Re: Bolt grade

The grade 8 bolt dosen't need to be tightened to "yield" crushing the material it is clamping, only to the needed tightness. As far as "Overkill isn't always best... its better to match the material/tool to the requirements.", Let's imagine you are working on a 5,000 lb. boat, it slips and you are being crushed under it. There is a 10,000 lb capacity forklift there, are you going to tell the rescuers "Wait, you need to go get a smaller forklift"?
 
Scott Danforth

Scott Danforth

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Re: Bolt grade

Chris1956 said:
You sweetwater types can indulge yourselves with coated steel bolts. It is much better to use Stainless Steel here on the salty coast. 4 SS 1/2" bolts are much stronger than the transom bracket of the outboard.
Click to expand...

we use coated steel boats for naval, military, and yacht products at work. call me what you want, I actually understand bolted joint theory, metallurgy, and corrosion. SS bolts are about as strong as aluminum
 
dingbat

dingbat

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Re: Bolt grade

smokingcrater said:
Overkill isn't always best... its better to match the material/tool to the requirements.
Click to expand...
+1
Apparently people don't understand the difference between shear and tensile force. If they did, they would understand why you don't need #50,000 tensile strength, grade 8 hardware to mount an #250 outboard to a #18,000 tensile strength fiberglass and wood transom.

These is a positive, you wouldn't have to look for new bolts when the transom was ripped off the boat. :lol:
 
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Chris1956

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Re: Bolt grade

Scott, If you think SS bolts are as strong as aluminum bolts, you need to do some more research.
 
Scott Danforth

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dingbat

dingbat

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Re: Bolt grade

note, the 7075-T6 aluminum has a higher tensile and yield than the 304SS does.
Click to expand...
Good luck finding 7075 bolts......lol
 
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