Bolt grade

[bruceb58]

Re: Bolt grade

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.

This is a good explanation:
Proper Bolt Torque - by Zero Fasteners

A properly tightened bolt is one that is stretched such that it acts like a very ridged spring pulling mating surfaces together

In order to get that same tension in a grade 8 bolt vs a grade 5 bolt, the torque is more because the yield strength is more on the grade 8 bolt.

 

[Fun Times]

Re: Bolt grade

To try and help cut through some of the confusion due to it seems that cabin fever may have plagued some of iboats top performing forum members this year! :faint2:, Below is the information for the Yamaha OEM recommended bolts for 115 up to 300 HP and F115 up to F350 HP engine models.

Select the transom mount bolt due to the boat transom thickness.
Boat transom thickness (T), Mount bolt size, Bolt P/N,
55 ? 65 mm(2.17 ? 2.56 in.) M12 ?115 mm 90101-12M03
65 ? 75 mm(2.56 ? 2.95 in.) M12 ?130 mm 90101-12M05
75 ? 95 mm(2.95 ? 3.74 in.) M12 ?150 mm 90101-12M77
75 ? 95 mm(2.95 ? 3.74 in.) M12 ?150 mm[High tension bolt] 90101-12031
95 ? 115 mm(3.74 ? 4.53 in.) M12 ?170 mm[High tension bolt] 90101-12036
*High tension bolt is recommended to F300 (V8)/F350.

Bolt Torque reference:
M8:18 Nm, 1.8 kgfm, 13 lb?ft
M10:36 Nm, 3.6 kgf?m, 27 lb?ft
M12:52 Nm, 5.2 kgf?m, 38 lb?ft

4. Apply a sealant to the mount holes, and se-cure the motor with supplied mount hard-ware. For tightening procedure, first tighten the in-side nut, then the double nuts each other.
*Tighten the mounting bolts/ nuts by suitable torque due to boat transom structure, material, design, etc.

Page 1-8, Rigging Guide - Yamaha Outboard Motors 2011