Re: oil transfer line?
Are you talking about item 23 in this link?
Mercury, Mercruiser, Force, etc. - CYLINDER BLOCK AND CRANKCASE ASSEMBLY - 40 HP30 JET
If so, from the manual:
NOTE: The bleed check valve allows excess crankcase
lubricant to flow one way, from the bottom of the
crankcase to the top end cap bearing to provide additional
lubrication. Inspect check valve for proper operation
by applying vacuum to outlet side of check
valve (barbed end). No restriction to flow should be
felt. Apply vacuum to threaded side of check valve.
A restriction to flow should be felt indicating check
ball is seating properly. If these test results are not
obtained, check valve must be replaced.
If you would like a copy of the service manual, send me a PM with your engine s/n and an email address.
Gerry