To properly test a GC it must meet two measurements one involves pressurizing the GC with an air pump. ( this confirms oil will not leak out during operation .. egress) The drained of oil GC should retain about 10-12 PSI for a few minutes. IF the pressure drops spray soapy water on the drive, shift and prop seal areas to identify the culprit. Prop shaft seal are the usual bad ones due to monofilament spooling in the GC and destroying the seal. Pull the propr and check!!
The second test is a vacum test to measure the GC capacity NOT TO LET IN any water when the GC cools off after long runs. Cooling reduces the inside pressure and tends to suck in water (ingress)
Here is a good video explaining it. But don’t let that discourage you.. That Ob looks pristine. JUst check out the wiring in case it is brittle and crumbling… it may not be of course
worst case scenario some folks just dump the GC oil mid season and refill with fresh. ….saving the cost of a reseal job.. Oil is cheap!
I purchased that pump in the video on Amazon ..wors fine… the real thing is $100+ the pumps checks pressure and vavum
Joining AOMCI has priviledges 🙂