hey welcome home brother,, i went over in 68 but to china but in an old diesel electric submarine, spyboat, i was involved in a runaway fairbanks morse 10 cylinder opposed crankshaft 38 ND 8 1/8, if i cudn get it shut down they were going to close the hatch on me and let it suck a hard vacuum on the engine room, scary, i threw rags and eventually put a trash can over the ibtake basket, lost a blower seal and was sucking lube oil, and those fairbanks had a lot of that,, on your little yanmar/kubota, there are only 2 ways to get runaway, a blown seal on the turbo or some failure inside the FI pump, look inside the air downstream side of the turbo, that is on the intake side, pull a hose or something, if its dry, the pull ur inj pump and put it in the injection shop, pump repair is lots cheaper than a total engine replacement, ive heard a few detroit diesels run away and they can make just an incredable amount of noise on runaway, if you are anywhere near them when they make that ahWHOOOOO NOISE YOU WILL Forever think you were waaaayyy too close, buck,, pull the hose between your turbo and the intake manifold, if its clean and relatively dry, bite the bullet and take your pump to an inj shop, buck