1954 mark 20 spark plug

Jimmygreentop · Apr 28, 2013

what kind of spark plug should be used for this motor

Fun Times · Apr 29, 2013

Do you know if you have a mark 20 or a mark 20H as they both have different spark plug numbers.

http://www.mercruiserparts.com/selectModels3.asp?type_id=MARK

Mark 20, see item number 43,
http://www.mercruiserparts.com/Show...=1712&bnbr=50&bdesc=MAGNETO+ASSEMBLY+(KH,+MK)

Mark 20 H, see item number 46,
http://www.mercruiserparts.com/Show....png&inbr=1711&bnbr=50&bdesc=MAGNETO+ASSEMBLY

If it an 20 H, good luck with cross referencing the part number 33-20982.

Jimmygreentop · Apr 29, 2013

I am not quit sure it says K mark 20 on front cover serial # 804808

fastjeff · Apr 29, 2013

It's probably not a Mark 20H--they're gold (in more ways than one).

Use Autolite 303 plugs or the equivalent. Gap at .025 ".

Jeff