Thanks for posting them blog. I recently had mine tightened/adjusted by the local diesel service company. It was a simple job if you have the wrenches and knowledge on how tight it should be. They did some other work at the boat, but marine services are still expensive... ferrari repair prices for 50’s technology - reminds of the aviation business. I think I will do it myself next time.
This is definitely something you can do yourself!
For a stuffing box with conventional packing, just adjust it so that it drips slightly with the engine in gear. Indeed, one way to see that it's right is to look right where the shaft exits the stuffing box nut/gland on its way forward to the transmission. If you can see a glistening of water right where the shaft protrudes from the nut, that's good enough. It doesn't need a lot of water to cool it but it does need some--and that goes for the "virtually dripless" packing as well.
Run the engine in gear (the boat can be tied to the dock) and, being careful not to get in the way of any of the engine's moving parts, feel the stuffing box nut. It should be anywhere from cool to warm to the touch. It should not become so hot that you can't keep your finger on it.
Remember that it's better to let it drip just a bit than to run it bone dry. You can always sneak up on the adjustment in small increments. That is, run it maybe a bit on the loose side for a while and then tighten it just a bit and run it some more, checking temps.
Having the right wrenches makes the job much easier. Some people use those adjustable plumbing wrenches from Home Depot, but they are wretched. Buy dedicated open-end wrenches that fit the stuffing box nut as well as the retaining nut. On my little stuffing box on my E26, those happen to be 1-7/16". Yours may be (probably will be) different. It makes the job so much easier. Realize that those nuts are not necessarily precision made, so I have found that, depending upon how the wrench is oriented with respect to the nut, the fit may be either kind of tight or a bit sloppy.
If you do need to apply a penetrant (e.g., PB Blaster) to free the lock nut, just be sure that you don't spray it on any rubber parts. So avoid getting it on the stuffing box hose as well as the rear oil seal for the transmission.
Anyway, since this is a job you will need to do from time to time, you don't want to be at the mercy of a "local diesel service company"--certainly not for a job like this.
You can do it!