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Old 07-04-2006, 10:17 AM   #1
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Bolts for an outboard????

ok I went to buy some bolts before I found this site and have been questioning the idea that they might not be right for it. I bought some course threaded stainless bolts that fit nicely, but I was wondering whether a fine thread would be better. I am unsure as I thought the course thread would have a stronger hold, but alas I do not know....Help. I also only have 4 of these bolts holding the 275 on too should I have more???? I am not racing so I wont be giving it grief its only for recreation :P
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Old 07-04-2006, 11:09 AM   #2
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should be half inch UNF I beleive

Genuine merc ones are about £100 a set!
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Old 07-04-2006, 11:40 AM   #3
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hmmm my set was about £10 :P The nuts and bolts ppl said it would be strong/ fine (questionable), but then my question is that why do merc sell theres for £100 and I bought some from a marine nuts and bolts place for 10. Sheesh Its just a jungle out there.

and whats half inch UNF? I am new to all this milarky :P and where can I get them cheap??
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Old 07-04-2006, 12:54 PM   #4
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Quote:
Originally posted by divertom


and whats half inch UNF?
It is an imperial size fine thread
1/2" is approx 12.5mm in todays money so i suspect the ones you have purchased are normal M12 s/s nuts and bolts. The fine thread simply allows more threads to be in the nut thus making it stronger. Unfortunatly no one seems to stock the 1/2" unf bolts in the length you require so you have 6 options
1. Run the M12's (I do on the bottom lift bolts on mine but i wouldn't risk it on the top bolts)

2. Buy some 1/2" UNF threaded bar and make some bolts by welding nuts onto one end of it. ( again ok ish but you don't get any land on the bolts so they are again slightly weaker.

3. Run with M14 nuts and bolts. ( i've heard of a few people doing this but haven't tried it myself.

4. Bite the bullet and purchase some genuine mercury s/s bolts with brass nuts.

5. Find someone in the states that can send you some as they are common over there.

6. Someone on this forum will see this thread and have some you can buy
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Old 07-04-2006, 01:26 PM   #5
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6. Someone on this forum will see this thread and have some you can buy
My ears are burning. What length does sir require, and how many?
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Old 07-04-2006, 01:41 PM   #6
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Da dah dah da da da daaaaaaah


TD Comes to the rescue!
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Old 07-04-2006, 04:02 PM   #7
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from what I remember the threaded bit is like almost 12mm diameter, then the head is a 17mm. The engine did come with some good top bolts I assume there the bomb as they are stainless M17 fine threaded. So i'll keep them. The bottom ones are a length of 80mm from what I remember. I assume I just need two good ones for the bottom. What ya got??? how much? and do you have any?

This site rules too
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Old 07-04-2006, 04:05 PM   #8
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P.S as you can tell my knowledge with bolts is not that good :P but I suppose thats what this forums for right
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Old 07-04-2006, 04:06 PM   #9
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correct.

and the occaisional bit of piss takin
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Old 07-04-2006, 04:46 PM   #10
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yeah ,wheres my graphics ................every chance i get
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Old 07-04-2006, 05:02 PM   #11
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you've not quite got the message have you nobby
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Old 07-04-2006, 05:05 PM   #12
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right thats it im going to send you some really tasteless pics now
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Old 07-04-2006, 05:07 PM   #13
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I do hope they arent 'Action' shots.......... I'm not so sure I need to be seing 'Mini Carly'.................................. I'm still scared from 'Mini Gav'!!!!!!
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Old 07-04-2006, 05:08 PM   #14
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you've just given my client a fkin ceasure!

you great purple dildo
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Old 07-04-2006, 05:11 PM   #15
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do you want me to stop because theres more,i only want a blue stripe and a black chequered flag
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Old 07-04-2006, 05:12 PM   #16
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I'm retired!
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Old 07-04-2006, 06:24 PM   #17
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you guys are crazy
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Old 07-04-2006, 10:21 PM   #18
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When in tension a bolts strength is proportional to its minor diameter. The minor diameter is the diameter at the bolts narrowest point, which is between the valleys (as oposed to the peaks) of the threaded part.

So, land on the bolt doesn't really make a difference to tensile strength.

A fine threaded bolt has shallower valleys and thus a larger minor diameter than its equivalent sized coarse threaded bolt. Thus it has greater tensile strength.

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Old 07-04-2006, 11:50 PM   #19
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geek
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Old 08-04-2006, 10:13 AM   #20
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What about stress risers the bottom of the V on the thread?

Quote:
Originally posted by Johnny Boat Dude
When in tension a bolts strength is proportional to its minor diameter. The minor diameter is the diameter at the bolts narrowest point, which is between the valleys (as oposed to the peaks) of the threaded part.

So, land on the bolt doesn't really make a difference to tensile strength.

A fine threaded bolt has shallower valleys and thus a larger minor diameter than its equivalent sized coarse threaded bolt. Thus it has greater tensile strength.

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