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T

thornbury

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"Could someone please tell me

"Could someone please tell me what threads are used on a 1988 Evinrude. Are they UNC? Here in the UK our old, pre metric threads are BSW, BSF etc. I've seen mention in postings of bolts such as No. 8 1/4-20, is this a grade for the "8" 1/4 inch at 20 tpi and is this UNC/UNF. I hope someone can enlighten me. Have the more modern Evinrudes gone over to metric?"
 
"Almost certainly 1n 1988 it w

"Almost certainly 1n 1988 it was all UNC and UNF

UNC threads are mostly the same pitch as BSW although the thread form is different. 1/4" UNC and 1/4" BSW are for example both 20 tpi.

UNF threads are finer than BSF. 1/4" UNF is 28 tpi, 1/4" BSF is 26 tpi.

I would not know if later engines have gone metric, doubtful, still use feet, inches, pints, gallons (and those are not real Imperial gallons) etc. over there. I don't think they know what a millimetre is!

An easy way to check is from the head size. UNC and UNF are a whole number 1/16" across the flats, unlike our old BSW and BSF while metric (Fine and coarse) are a whole number of mm."
 
"Thanks very much for that Vic

"Thanks very much for that VicS, at least it gives me a start with the rebuild - various snapped bolts."
 
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