Jabsco Bilge Pump - Sanity Check

[Durcott]

Good evening All - a quick sanity check if I may -

I see there is a Jabsco 23680-4003 bilge pump unit in this boat I've recently bought. I've not met such a heavy duty pump before; more used to the little buzzy things with the red top...

It's on an ac MCB (I know - no dc rating etc...) which pops after a few seconds. So I wondered if it was stalled and started to investigate. It looks OK - hardly used. With the brass cover plate fully tightened, the motor runs fairly slow, making a 'pop-pop-pop-pop' noise. With the plate slackened, the motor runs much faster with more of a 'whizzzzz' like a Rule pump.

I THINK this is OK, but it could be a sign that the impellor is the wrong size and it's binding on the plate (There is loads of lube by the way).

So - are these pump motors supposed to run slowly or fast?

Jeff

 

[Graham_Wright]

Sounds like it could be a dodgy electrical connection or inadequate wiring. Check the volts at the motor when it's under load.

 

[oldmanofthehills]

AC MCBs dont like DC. I have one for my ebi and it pops randomly (but mostly ok). Additionally I cant determine what current that pump takes. So what is its load and what is the MCB rated at ?

 

[rogerthebodger]

AC MCBs dont like DC.

Nonsense MCB will handle DC with a lower voltage rating to cut down on the arcing you can get with switching DC

My whole DC distribute board used MCB as overload devices without issue for 15 years

 

[Bilgediver]

Good evening All - a quick sanity check if I may -



I THINK this is OK, but it could be a sign that the impellor is the wrong size and it's binding on the plate (There is loads of lube by the way).

So - are these pump motors supposed to run slowly or fast?

Jeff

The fact that the pump runs slow when you tighten the cover plate suggests there is something wrong with the pump and the extra friction is creating overload so blowing the MCB . If this is an impeller type pump the problem could be an aftermarket impeller slightly over size or the wrong thickness cover gasket. Chart paper makes good gaskets and I would suggest adding another layer of chart paper. The pump should run the same speed regardless of the cover being loose or tightly bolted.

 

[Boater Sam]

The impeller is either the wrong one or it has swelled ( possibly with it getting oily ) so that it is too thick for the pump chamber.
I would take it out and rub it on sandpaper to slightly reduce its thickness.

 

[oldmanofthehills]

Nonsense MCB will handle DC with a lower voltage rating to cut down on the arcing you can get with switching DC

My whole DC distribute board used MCB as overload devices without issue for 15 years

May depend on the brand, none of my recycled 32a ac one hold in reliably on 12v dc - and we are not drawing 32a. Mostly ok but sometimes several goes

 

[rogerthebodger]

May depend on the brand, none of my recycled 32a ac one hold in reliably on 12v dc - and we are not drawing 32a. Mostly ok but sometimes several goes

My brand of MCB do quote a DC rating printed on the MCB mine are merlin gerlin

What brand is yours so we can look up the spec and see what the manufacturer

 

[Boater Sam]

Merlin Gerin ( now Schreiber ) are approved for low voltage DC. I used many thousands of them in telephone switching rooms.

 

[Durcott]

The fact that the pump runs slow when you tighten the cover plate suggests there is something wrong with the pump and the extra friction is creating overload so blowing the MCB . If this is an impeller type pump the problem could be an aftermarket impeller slightly over size or the wrong thickness cover gasket. Chart paper makes good gaskets and I would suggest adding another layer of chart paper. The pump should run the same speed regardless of the cover being loose or tightly bolted.

Ahh - thankyou Bilgediver. That makes a lot of sense.

 

[Durcott]

The impeller is either the wrong one or it has swelled ( possibly with it getting oily ) so that it is too thick for the pump chamber.
I would take it out and rub it on sandpaper to slightly reduce its thickness.

There is a fair bit of oil in the bilge, so that's a good call. Thanks for the insight.

 

[Durcott]

Ahh - thankyou Bilgediver. That makes a lot of sense.

There we have it - cover gasket called up in Jabsco parts list. No cover gasket installed !