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I need to know a spec for engine mount bolts, when using solid mounts !!!!!

I would like to buy new bolts for the engine mounts both top and bottom as I have made solid mounts.
The bolts are not in bad condition, but someone mentioned to use the best grade bolts as the original top mounting
Bolts could break when using a solid mount ? is this true ?

the original bolts have cleaned up fine, so not sure about using these now.

The bottoms are fine as I will be getting stainless for these as only under high pressure when reversing (not very often).

bolts from steering arm to top mount have also cleaned up nice and would need new nyloc nuts, but again have a slight problem.

not knowing exactly what the spec was would simple grade 8.8 be good enough or do I need a higher grade.

I would of liked to use stainless steel, but it seems that stainless bolts are a lot weaker than even 8.8 ?

any thoughts on this, or any ideas how to stop corrosion on steel bolts would be good.


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Stainless reacts with aluminum, grade 8 bolts is what you want

cheers sharpeye mike.
didn't think about the stainless and reacting.
grade 8 I can get so will do.

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there has been a lot of discussion on various forums about this subject.
Now - I'm no "expert" but this connection is obviously very important and is under a lot of stress, especially for a performance boat.
Lots of folks will go with the "this should work" thought process, but if you want to be sure, I would get a set of bolts from a dealer.
I know here they go for about $50.00 and up. If your paying less, then I would try somewhere else.
The ones I use are the mercury ones, and they are about 1/2" fine thread stainless with a brass looking nylock nut. I don't think it's actually brass, but some other metal.
Don't over tighten those bolts, as you can crack your transom and weaken it.
I'm glad too see you are asking about this instead of just throwing some "good enough" bolts onto your boat.
Cheers

Sorry wildcat, but your talking about the wrong bolts. easy mistake to make.
I am talking about actual engine mounts to the brackets, NOT engine bracket to transom.
The mounts you cannot see unless the powerhead is taken off the midsection.

I know about proper transom bolts, but the ones I needed to know about are when stripping the engine down and
replacing the rubber bushes with solid mounts.

but you are correct in that using proper transom bolts is a must, and need to be around 60ft pounds or what ever the bolts
torque settings can take.
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Oh - ya - I know the ones you mean. Sorry. They some Big A$$ bolts. Not sure on the spec?