Jabsco 36900-1000 pressure water pump problem advice

tmjb

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Mar 13, 2012
222
Hunter 36C Glen Cove
I have the above on the fresh water system of my ‘81 Hunter 36 which I have owned since late 2014. It worked very well initially and then required replacement of the typical diaphragms that come in the service kit about two years after which it worked well again.

Having worked fine when I winterized the system last fall when I flushed the system just recently it also worked fine except that just as it completed pumping the system up to pressure it would blow the circuit breaker. This condition related each time I opened and closed a faucet, ie it otherwise functions normally.

Does this sound like it could be caused by a faulty pressure switch?

I appreciate any advice anyone can provide.
 
Nov 6, 2006
9,885
Hunter 34 Mandeville Louisiana
Might be a bad circuit breaker.. you'll need an ammeter to see what current the pump is drawing.. if less than the pump rating, the breaker is bad..
Could be that the pump motor has internal problems.. the ammeter will show that as a current bug enough to trip the breaker.
 

capta

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Jun 4, 2009
4,766
Pearson 530 Admiralty Bay, Bequia SVG
I have been using these pumps for around 50 years and don't remember having that problem unless the motor was in need of cleaning, repair or replacement. I doubt that it has anything to do with the pressure switch, but it is the cheapest and easiest part to change out. Perhaps a brush has worn down and the spring is contacting the commutator or the commutator is dirty. It is actually pretty easy to take apart these motors and clean the commutator and/or replace the brushes. When it is apart, check the bearings and lubricate before reassembly. It is the same basic motor as the Water Puppy and many other Jabsco pumps.
The hardest part is holding the brushes open to slip back on the commutator when reassembling, but if you are mechanically adept, it shouldn't be a problem. Clean the isolators between the commutator contacts with a small piece of a fine tooth hacksaw blade, but do not score the commutator contacts.
 
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tmjb

.
Mar 13, 2012
222
Hunter 36C Glen Cove
Many thanks for the speedy and informative replies.

I do have an in line filter which I checked and seemed pretty clean. I’ll fully clean next time I am aboard.

I also noticed that my battery monitor went from indicating a few amps as the pump ran normally to a steadily increasing draw as the pump slowed down and stopped following which the breaker flipped.
 
Feb 20, 2011
7,990
Island Packet 35 Tucson, AZ/San Carlos, MX
I also noticed that my battery monitor went from indicating a few amps as the pump ran normally to a steadily increasing draw as the pump slowed down and stopped following which the breaker flipped
I'd switch out the pump and see if it still happens.
 

tmjb

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Mar 13, 2012
222
Hunter 36C Glen Cove
Unfortunately these pumps, while very good (I think?), are around $600 each so switching it out is not (for me) a realistic option. Thanks for the suggestion though. Any and all input is much appreciated.
 
Nov 6, 2006
9,885
Hunter 34 Mandeville Louisiana
Increasing amperes then a trip as the pump slows is most likely a bad pressure switch..the pump sees more and more back pressure which raises the amp draw and if the pressure goes much above the pump rating, the ampere flow will get big enough to trip the breaker.. Switch is usually easy to get at to clean and check.. It is usually a piston that pushes on a microswitch .. when the piston overcomes its spring at set pressure, it trips the microswitch and shuts down the motor.. but.. it can still be a bad motor as well.. ..
EDIT: if you find a bad motor, something like this should be fine for your boat: https://shop.sailboatowners.com/pro...5+GPM+Water+Pressure+Pumps+with+By-Pass+Valve
 

tmjb

.
Mar 13, 2012
222
Hunter 36C Glen Cove
Thanks again. Given that price and amp draw range is not very significant, what GPM is most appropriate 4, 5 or 6? Is there a reason other than amp draw not to go with 6 GPM?
 
Nov 6, 2006
9,885
Hunter 34 Mandeville Louisiana
Using one faucet at a time, 4 GPM is plenty.. 6 is a lot unless you have a big accumulator.. Without the accumulator, the motor will run in short bursts and it will not last as long as a lesser GPM rated pump..
 
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Feb 14, 2014
7,400
Hunter 430 Waveland, MS
Is there a reason other than amp draw not to go with 6 GPM?
Many reasons can affect flow rate.
GPM = Amp load
Maximum GPM is affected by...
1) Consumption Valve opening...[faucet opening]
2) Size of line
3) Distances...
4) suction filter plugging
5) Pinched supply line
6) No suction filter and diaphragms have crap in them
7) etc.

But what has changed for you from above?
if answer is nothing...
Check the breaker or pressure switch.
Jim...

PS: Or clean your motor per @capta
 

SG

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Feb 11, 2017
1,670
J/Boat J/160 Annapolis
I have two heads (on the boat, not counting the ones on necks ;^))) ). I don't think pressure with a 4GPM proper pump is an issue.

We have a an accumulator tank because our boat came with the same type of "old" pump you have. When they first came out, a "new", out of the box, Surflo non-reciprocating pumps cost only a bit more than the rebuild kit on the old Jabsco's alone. Further, they lasted "a lifetime". Now the pumps are more sophisticated and you can't get a constant rpm pump, their variable speeds and have become more expensive. Shop around and buy one. They still "last a long-time". We installed one with and left our accumulator tank in. That way, at night, if you get just a little water, the pump doesn't cycle.
 
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