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What size spanner for Mercury Powerhead Nuts

M

murdmerc

New member
I'm about to remove ... ahem...... Try to remove ... the powerhead from my 1991 40hp 2str. 4cyl. engine. I've disconnected all the ancilliaries and have cleaned up and being WD-40'ing the hell out of the 8 x nuts for the past 48 hours. Trying desperately to avoid bolt/stud breakage. The only thing is I'm a bit unsure as to what spanner to use - I only have metric and my 10mm is too small and 11mm too loose - I guarantee it is going to round the nuts - So reckon as it's an American motor I will need to buy an imperial spanner but there doesn't seem to be much available between the 10mm and 11mm size. Is 13/32 the correct size ? Anyone know for sure ? - The Nut is officially listed as 11-64809 - NUT (5/16 IN.) at http://www.hbmmercruiserparts.co.uk/...nd=543&bid=140 I guess that 5/16th is referring to the thread size.

See Nuts at : http://flic.kr/p/bvY7Bv
See Engine Details at : http://flic.kr/p/bvY7Bn

Cheers
 
5/16"=
0.3125"=
7.9375mm
stud size

13/32" or 27/64" are between 10mm & 11mm nut size
 
Last edited:
Love those tiny nuts on large studs! I suggest you buy 6 point open end wrenches (Sears). You probably need a 7/16 " size.

Jeff
 
I'm going to guess you're in the UK. Halfords have a socket set with imperial.But you'll need the spanners as well,probably in the same box.7/16, 3/8, 5/8, 9/16, are the ones you'll need most.As Jeff says ,open end.
 
Forgot to add this: I keep a cheap set of wrenches that I grind thin on the open end end so they will fit in tight spaces. I call them "Crazy Carl Wrenches" over the guy I hold responsible.

Jeff
 
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