|Knut had 99 problems, but a stuffing box wasn't one of them|
Unless your name is Pardey, or perhaps you are a Viking longboat re-enactor, if you are a sailor, you will eventually encounter the problem facing most boats: their hulls are full of holes.
|The Platonic ideal of getting stuffed.|
There are right ways to address this necessary, if counter-intuitive, state of affairs. Standpipes, for instance, are centralized inlets from which the various water needs (head flushing, engine cooling, seawater for washing, etc.) are "teed-off". If something clogs the inlet, crack open the top of the standpipe, which is above the waterline, and plunge with vigour. Packless or dripless shaft seals keep the water necessary for cooling a turning prop shaft inside the shaft log...and outside of the boat's interior.
|Photo copyright S/V Sarah: You can imagine accessing this rudder post stuffing box on a wild night offshore if you found water pouring in back here.|
Other, similar types of stuffing boxes are found in rudder posts. Thanks to the craze for aft cabins, this can be a hard place to even find, never mind effectively service. You need to swing a wrench or two.
|Rain ingress from Alchemy's companionway, not (I suspect) from the dripless stuffing box|
There are no perfect solutions, and some solutions actually require some imperfection. Such is the still-ubiquitous stuffing box, which keeps water not entirely out.
|A fairly typical "conventional" stuffing box, which is designed to cool via dripping, which is why engine compartment bilges slosh around small amounts of oily water and look filthy. Photo (c) alberg30.org|
|Fairly representative diagram of the heart of the matter: Alchemy's former stuffing box was set up like this.|
Tightening Valiente's stuffing box did nothing except express some grey thready goop out the front face of the stuffing box (actually a sort of hollowed out nut). Clearly, the increased use of the motor, or a sub-par installation the last time (about four years ago, on the hard) had worn out the packing.
|Packing rings on a very clean stuffing box. Photo (c) Compass Marine How-to|
As it turns out, a close examination revealed both wear and the incorrect installation of the wrong-sized packing, alas, by your humble correspondent.
|Convenient, if not cheap|
|Our youngest crew takes the drying-out opportunity to de-weed the shaft and prop.|
|Looks like a Scout project, doesn't it?|
|Not thrilled with the VC-17 performance this year. Son, however, has improved.|
Stuffing boxes are really about finding the sweet spot between dripping and cooling. Some experts apparently like to screw the stuffing box nut tightly, because the compressed and lubed packing needs to "settle in" or compress to its final shape. The "settling in" part is correct, but not without adequate water flow. The customary process is to leave the box loose enough (and yet secured with the locking nut, of course) to have some arbitrary number of water drops per minute coursing through the packing.
Then you run the engine in gear. You feel or use a temperature gauge to determine that the water flow is adequate to cool the stuffing box.
Only then do you tighten down the box incrementally, until the flow is low enough to keep you happy about your bilges, but high enough so that the box never gets warmer than you can touch.
It's tricky and it's individual based on the water flow inside the log, the engine speed, the type of packing and lube and even the water temperature. The goal is (usually) about one or two drips per minute, maybe a few more under power. No drips or "too warm to touch" is burning up your packing and even damaging your shaft.
|Nice day for lighting up the back of the engine compartment, crap day for actual sailing...no wind|
|Needs a scrub, yes, but no longer a bucket.|