Bolts for an outboard????

[JamesM]

Originally posted by Matt
What about stress risers the bottom of the V on the thread?

??? go on then!!!

[Matt]

What about using titanium bolts. 30% stronger than steel, 50% lighter, and 2000% price? M12x1.25x120mm=£41.99 each.
But imagine the bling.

[Captain Chaos]

@ 42 squids they aint that much more expensive than geniune merc ones!

[Jono]

You're all a bunch of useless tossers..... Nip up to B&Q... they'll have some nice M12 all-thread.. that 'n a couple of those really super nuts they sell (100 for two quid) and Bob's your Uncle.. No point spending money on any of this high tensile shit... I mean.. it's only yer engine that's being held on... not like summat important is it?

[Matt]

Boring trivia - apparently the SR-71, built for spying on russia, was also made out of russian titanium, and used almost all the titanium that the US owned at the time.

[JamesM]

I've often wondered why people don't use titanium bolts. They're stronger and longer lasting than stainless steel (aren't they?) and in the grand scheme of things the extra cost really isnt much at all.

[Matt]

I "thought" they're stonger than high tensile steel bolts, about the half the weight, and have the corrosion resistance of SS. But am not sure, hence the question.

[JamesM]

I guess it depends on the grade of titanium used but the ones I've seen on the internet are comparible if not a bit stronger in tension than grade 8 high tensile, so alot stronger than 304 or A2 stainless. They were $15 each for 1/2-20 x 3 3/4 inch UNF. As I said before I wonder why people don't use em $60 isnt alot when you've spent thousands and thousands on your outboard and boat. Anybody have any ideas?

[Matt]

That's somewhat cheaper than these mutha's!

http://www.tastynuts.com/acatalog/in...ml&CatalogBody

[JamesM]

http://www.racebolts.com/store/Titan...4-P228C55.aspx

$14 plus shipping and duty etc.

[Matt]

Yeh, I just googled that one. Some very creative pricing by the british companies.

It's almost shame I don't have any need for any new bolts. What about Chaos, he must need some more bling.

[JamesM]

3 3/4" is about 95 mm which may not quite be long enough though. That seems to be the longest they do in 1/2 inch.

[Burnett]

Originally Posted by Johnny Boat Dude

I've often wondered why people don't use titanium bolts. They're stronger and longer lasting than stainless steel (aren't they?) and in the grand scheme of things the extra cost really isnt much at all.

In the grand scheme of things then a few ounces saved by titanium bolts is of negligible benefit really.
Honda once used titanium in conrods on the NSX, but this was not only for strength, but also to reduce stress on the other engine internals when the rods are flying up and down the bores countless times a second (less weight equals less inertia) so the engine will be less stressed at high RPMs.

The problem with the SR71 (and all titanium come to that) is that it will eventually develop stress fractures if it's worked on with ordinary tools.

The SR71 had an entire tool kit specially produced for it made from steel which was 100% free of Cadmium, as apparently it's coming into contact with Cadmium that weakens the metal. Although how relevant this would be to a boat is negligible when you bear in mind that the SR71 was in service for about thirty years and was repeatedly heated and cooled to extreme temperatures every trip.

I wouldn't think it'd be worth it just for engine bolts to be perfectly honest. But then I know dick about boats! (Although I know a little about the SR71)

[$hooter]

If you guys would just buy a grade 8 bolt...I think they are 1/2" or 12.5mm in stainless...you will rip the transom off before the bolts fail. If anyone needs stainless bolts...holler at me and I will get them for you...no extra fees...just the cost of shipping and the bolts...fair?? Get the bolts and what we call over here..."fender washers". They are a large diameter washer to help distribute the load. For what you guys are doing, seriously it is not goiong to matter whether you have course or fine thread bolts...but you do want to have all stainless or black oxide grade 8. Do not mix the metals with alot of water involved.

[$hooter]

LMAO....WRONG

Originally Posted by Matt

Boring trivia - apparently the SR-71, built for spying on russia, was also made out of russian titanium, and used almost all the titanium that the US owned at the time.

[Matt]

OK. So the SR-71 wasn't made out of soviet titanium?

[Jon Fuller]

Originally Posted by $hooter

seriously it is not goiong to matter whether you have course or fine thread bolts

I totaly dissagree! And consider that bad advice.

Especialy if the motor is being bolted to a metal brcket or lifter, as apposed to a compressable timber/glass transom.

I've seen loads of course thread (metric) bolts losen in a metal to metal situation.

Why do merc, OMC, Yam etc, ALL supply fine thread motor mount bolts, if good old, easily available & cheaper, 'Course' ones are 'just as good' at the job?

You can bolt your motors on with 1/2 turn 'quick fasteners' for all I care, but I wouldn't reccomend anyone on here uses course thread bolts, 'especially' on metal to metal mounting situations (brackets) for mounting their OB's.

[BluFin]

Quite correct Johnny. Fine Threads resist vibration better & have a greater contact area.
If at some point down the road you need to cut the Ti bolt or nut...pain lots and lots of pain you have just gone and spent £100 or more on tipped blades & drills.

[Jon Fuller]

With the metal to metal joint, (Sadle to lifter/bracket) a good, fine thread, gives you a far higher mechanical advantage, thus leaning on the big spanner, induces a far higher 'pull' on the bolt, giving it a good 'stretch' and much higher clamping force. This I believe to be far more durable a location than a grotty course-er thread M12 or similar. Imagine taking the 'course' bit to the extreme, and trippling the pitch, how much pull would you achieve on the bolt with a given torque? feck all! Twood be like trying to fix a motor on a boat with a water bottle cap. And with an un forgiving metal to metal interface, it will soon all start moving, and going horribly wrong. As I say, an extreme example, but the priciple is just the same.

No contest as far as I can see.

[JamesM]

Originally Posted by Burnett

In the grand scheme of things then a few ounces saved by titanium bolts is of negligible benefit really.

Originally Posted by $hooter

If you guys would just buy a grade 8 bolt

Its not the weight saving but the extra tensile strength that I was interested in. Grade 8 high tensile isn't really an option when using them in salt water, so alot of people run two sets (4 bolts) of the standard 1/2 UNF 304 stainless bolts as they seem to think 1 set won't be strong enough, especially with a lifter/bracket and/or in a big sea. I only run one set and haven't had any problems as yet but if I could get a bolt that was twice as strong and didn't rust I'd happily pay say £15 to £20 a bolt as a single bolt failure could cost me a whole lot more than that.

As far as I know/remember:

304 stainless has a tensile strength of 70,000 PSI
Grade 8 high tensile steel has a tensile strength of 150,000 PSI
And the titanium bolts that I posted a link to have a tensile strength of 170,000 PSI

The only thing that has stoped me ordering any is simply that I haven't seen any evidence that anyone else is using this apparently 'ideal solution', so it leaves me wondering why? The link I posted is at the top of the list when you google 'titanium bolts' so its not as if it was hard to find.

So:

1. Is there a fundemental reason why using titanium bolts in this application is a no no?

or...

2. Are lots of people using them and I just didn't know?

or...

3. Is the 70,000 PSI thats afforded by 304 stainless far more than you will ever need even with lots of setback in a heavy sea?

or last but by no means least...

4. Are me and Matt world leaders in the arena of 'engine to boat attachment thinking'?