What size and grade bolts?

[Skydog]

To bolt a 280 to the transom?

Thank you Skydog

 

[K.Kiser]

1/2" x 13 stainless or grade 8 steel... The hardness of the grade 8 isn't necessary, but they stand up against corrosion a little better than the standard grade 5... If you go stainles, don't forget to go back a few times over the course of a month or so and check the torque and be sure to use anti-seize when you install... If you re-torque, be sure to spin the nut only and not the bolt to keep your seal... They'll stretch a little with the initial torque, but they'll eventually find a happy spot... The grade 8's won't need torqing but once, and 45-50 ft. lbs. of torque should be plenty on either fastener... You might have known all of this already, so I'll shut up..

 

[Skydog]

No no THANK YOU !!!!!!!!!!!!!!!!!!!!!!

Skydog

 

[hack02]

Fine threads if you can find them.

 

[Skydog]

Thank you

How long? Do you get the bottom ones longer than the top? No jack plates right to the boat.

Skydog

 

[GFinch]

As K.Kiser said "sure to use anti-seize when you install... "

I had the pleasure of one gaulling and had to take a die grinder with a cut off wheel to it. It was going on the first time and stopped short of tight by a 1/16", it was ugly!
Also never use an air tool to run them up.

 

[John Richied]

When you figure out how long of bolts you need you might want to get them a tad longer so you can double nut them. It might be over kill but I double nut my jackplate to engine bolts.

I like the stainless steel bolts and brass nylon lock nuts.

 

[K.Kiser]

If you use SAE( fine thread ), try to use a fine wire wheel to buff the threads a little... Fine threads gaul easily, even a "feather" can make them wedge to a stop... Also, fine threads clamp harder than coarse threads at a given torque, so you won't need as much as muscle on the wrench... This almost certainly won't be a problem with bolt sinking in an Allison, but use a little caution on a wood boat...