The piston had the first ring 1/8 inch from top of piston and used compression to keep it seal against cylinder. These failed due to carbon build up and rolling ring and damaging cylinder. I rebuilt over 2 dozen 55hp for high ring damages as factory would foot the bill in 1978-79
IMO Boyesen are junk and will last about 2 yrs tops. Will last 30 seconds if it ever sneezes. I only use the above, mostly Chris's reeds. If motor is new to you the intake may be crossed drilled which will effect idle a tad.
If seller can test and show bias circuit is good and box functions it might be worth a try. Might end up with one that dont work and no refund on used parts
Only use OEM, WSM, Serria or EMP switchboxes..The cheap Chinesem junk on Amazom can damage your engine. I have seen several posts on other sites where cheap boxes damaged motors
Engine block is considered engine ground and lower and upper cowl and brackets are cowl grounds. They the grounding straps from brackets to cowls to engine block
