Best two stroke diesels ever made, I would be going with a head gasket issue here. It does take special tools to set the injector pump height and exhaust valves bridges and the pump rack would just take a screwdriver and some skill. Water in the fuel would be a dead hit or a miss in the sparkplug world. Not sure of the air cleaners used here, but I would make a good look see, the blower uses a lot of air to force out burnt air in the cylinders.
