Chuck - Check this too ..
I bought my '85 H31 four years ago in St. Pete, Florida. On the run up to Oriental, NC, I ended up with a drip that I couldn't stop. I found out later, that someone had put teflon packing in the stuffing box. Repeated adjustments to stop the drip had caused the teflon to "score" the driveshaft. I ended up replacing the shaft & the stuffing box. It's a good idea to have your yard check the packing & check the shaft too. Once you have gone this far, consider replacing the cutlass bearing too. A note of warning is in order if you end up disturbing the engine/shaft alignment. On early H31s, the clearance between the shaft & the tube that it exits from the boat is a very close fit. Proper engine to shaft alignment is critical. If it's not aligned properly, the shaft will "thump" intermittently at different rpm ranges depending on Yanmar vibration. I am told that Hunter "opened up" this clearance on later H31s. My H31 is back in Florida now - in Charlotte Harbor. The diesel performed flawless on the 1000 mile trip down here. Hope this helps.