2001 Yamaha 200 OX66 low compression

[Dudefishsn]

Howdy Y’all,
I am a new member as of today. I have a 2001 Yamaha 200 OX66 that had sat for about 4 years. Someone had tried to idle the engine with bad fuel for about 2 minutes before properly it finally stopped running. The VST was full of fuel and water, and is now shot, as well.
The compression now is 150 in four cylinders, and 130 and 90 in another cylinder. The motor is at a shop now. I had heard shooting oil down cylinders can sometimes (in rare cases) loosen stuck rings which can possibly free stuck rings improving compression. Mechanic states VST needs to be functioning (??). I am thinking that I should just replace motor with a used motor, and have looked at a 2001 Yamaha 250 OX66 (450 hrs $4000) or a 2005 Mercury 200 Optimax (750 hrs $3000 with rigging and throttle control)
Any thoughts, especially experienced ones can help out a huge amount. Due to disabilities, this is not something I can do myself or easily buy a brand new motor.

[TownsendsFJR1300]

I'd do a leak down test (with the bad cylinder at TDC) to rule out a bad head gasket first.

Pulling the head (or at least "scoping") would also help let you know what direction to go,
IE is the low cylinder scored, etc? Inspection of the head gasket too..

Possible broken head bolts are possible down falls as well (especially on an old motor) and of course labor...

Depending on what cylinder is super low, I see no reason why, with the head removed, remove the reed assembly which will
give you access to the connecting rods bolts. If there's room (lower cowl), you can pull that piston out, re-ring, etc.. The rods, (per the parts diagram
do have roller bearing but appear to be "caged")...


.