It has now seized solid with corrosion/rust/time, I guess, etc. I was thinking of replacing it with a Jabsco type, which is claimed to 'definitely' self-prime, and also be ok for moderate run-dry without damage.
Do you know of any other better pump to use in this situation, and which might be available in Australia..?
If it helps... we have had two Jabsco 18590-series macerators on board since OEM, 2002. One of those is for overboard discharge of the holding tank (where legal) and the other is our fishbox pump-out.
I'm just in the process of replacing at least one of those, the one for the fishbox... which has been used yearly, for about a month during the season I bother to fish, since we got the boat in 2005. This one needs to self-prime, and it has done that fine up until recently. Actually, that pump still works, but the symptom is a worn impeller. Not unexpected, over time. There's a re-build kit available, but my approach will be to replace, and then afterwards see about re-building the original, to keep onboard as a spare.
The OEM parts were 18590-0090 12V units. Replacement with Jabsco's current 18590-2092 12V unit is not hugely expensive, $145 from Amazon, and there were some slightly less expensive options.
Our other pump hasn't been working well for a couple years, I suspect primary because we're usually 99% inshore where overboard discharge isn't permitted. IOW, lack of use. The symptom for this one was at first that I had to manually spin the impeller shaft first, to unfreeze the mechanism. More recently, that hasn't worked. I suspect it's either really crapped out (
) or possibly equally likely, just seriously frozen with uric acid build-up.
I can perhaps replace it with the rebuilt unit from the fishbox application, replace it with new, replace it with a treatment system (e.g., Purasan), or maybe even just try to free it up with something liquid (Raritan's CH, muriatic acid, or some such. Of those, the treatment approach would give us best usage, but at highest cost. If the liquid wrench approach works, that'd be least expensive, but then we're just back to our original state, not using the thing inshore.
Anyway, mostly my point is that I feel like I've gotten my money's worth from these particular units.
For OP: George, I'd suggest you examine treatment options (e.g., Purasan, etc.). You may find those alternatives useful for comparison to a composting (dessicating, gentlemen must sit) approach.
I've read that holding tanks rarely contribute to "head" odors in a boat, that usually it's something about the various fittings... or sometimes the hoses themselves... that are the culprits. There's a way to combine your holding tank with a treatment system.
-Chris