You don't need a compression nor leak down test. Is it spewing blue smoke that smells like
oil? Is it using a lot of
oil? Is it just hard to start? Blue smoke is the rings and total
rebuild but you can
DIY. Hard to start is likely
exhaust valves burnt because of a prior overheat. Easy
DIY fix just take the cylinder
head off and take it to a machine shop. They will fix the compression problem by grinding the valve seats and replacing any worn valves and
seals then you can reinstall it with a new
head gasket. This is a 1 or 2 day deal. While the head is at the machine shop you can clean your injectors and get a new
exhaust elbow and
water pump impeller.
Don't listen to anyone that tells you to go pick up the mechanic at the
dock so he can do his "magical testing". Yanmar engines don't require hocus pocus just
fuel and compression. The time it takes to do a compression test on a yanmar is the same time it takes to
rebuild the entire cylinder head so spend your
money on testing or spend it on fixing it. Your choice.