Raw water pump on genset not pumping.

[Simi 60]

This is on the genset.
In December it had an auto shutdown.

I pulled the heat exchanger then, all good
I pulled the pump and impeller was all good
Strainer clean, no obstructions
Reassembled, ran for a bit and forgot about it.

Yesterday raining, auto shutdown again.
Water flow very low
Did all of the above again, all good but replaced the impeller while there
Now its simply not sucking water at all.
Any ideas?

To get us out of a pickle I plumbed in a 240v 22lpm centrifugal pump and we are away again seemingly better than ever and I will very likely set this up properly when the weather gets sunny again due to the near impossible location of the impeller pump.

. But, I would still like to know why the impeller pump was not sucking.

[Sparx]

Does the pump flow well when the pump discharge is disconnected from the heat exchanger?

Could there be air in the pump suction? Or a plastic bag stuck in the through hull?

[mvweebles]

Agree with Sparx. Check flow through thru-hull as follows. Turn off thru-hull valve, remove top of strainer (should be well below waterline), open thru-hull. You should see a healthy flow into the bilge. If not, you have some seaweed or something clogging the inlet side of the strainer. Depending on size of hose to thru-hull, you may be able to use a garden hose clamped to hose on inside of hull (either side of strainer, which ever is easiest to access a hose). Turn on garden hose and wait - pressure might blow out obstruction.

If strainer/hull is clear, keep working your way towards raw water pump to confirm not obstruction. Otherwise, recheck your impellor. If you've recently lost an impellor, make sure the exchanger has gotten clogged with lost pieces (sounds like you've already done these, so apologies if this is a dumb suggestion but I'm running out of advice ).

[Simi 60]

Plenty of through hull flow, plenty of flow through HE (I did say pulled and checked)

No pieces of impeller, old impeller fine but replaced anyway, all hoses clear.

ITS THE PUMP but what?

[MikkiDuda]

Might sound like a stupid question, but is the impeller spinning at the same rate with the pump shaft and the engine? Might be a sheared key. Also, is the cam inside the pump in the right place?

[Wotname]

Originally Posted by Simi 60

Plenty of through hull flow, plenty of flow through HE (I did say pulled and checked)

No pieces of impeller, old impeller fine but replaced anyway, all hoses clear.

ITS THE PUMP but what?

Impeller slipping on it's hub?
Worn or scored end plate / cover ?
Worn cam?
Leaking shaft seal (allowing air in)?
Incorrect gasket (i.e. too thick) on the cover?

[mvweebles]

Originally Posted by Simi 60

Plenty of through hull flow, plenty of flow through HE (I did say pulled and checked)

No pieces of impeller, old impeller fine but replaced anyway, all hoses clear.

ITS THE PUMP but what?

Although rare, I have seen shafts break. Doesn't explain why you're seeing low flow - would be zero with a broken shaft. Could be a worn pump body, but that seems very unlikely.

You've ruled out everything else. Replace the pump (I know, "captain obvious" to the rescue). Please update when fixed. I know just a generator, but this type of problem is a bit of a nightmare scenario for a guy like me with a single engine.

Good luck

Peter.

[Simi 60]

Its not the shaft, I put a blob of white paint on it through the weep hole gap, let it dry and spun it up.
Further evidence that the shaft was OK was when the engine was running, and the electric pump was working better than the on engine version ever has, the impeller now dry was squealing.
(Pours a bit of oil down outlet to shut it up)

I will not replace the on engine pump as I can get 4 electric versions for the same price and have it mounted right in front of me, easy access.
The on engine pump drew blood and caused excessive swearing and stress but probably caused me to lose a few kg in sweat so not all bad.

All I could think of was face plate gasket letting air in.
Piss poor slotted screws used to get crank on paper gasket.

Main engine had similar problem once.
Screws replaced with hex head bolts
$1000 spent on spare direct swap pump.

I should add, I had threatened to do this a while back.
Looks like now is the time.
Glad I had that green pump in reserve and half a plan in place.

http://www.cruisersforum.com/forums/...ch-204159.html

I still need to finalise that power situation in post 5

[Caliber40]

Following

[endeavour55]

try to run water thru a garden hose into the pick up hose just after the strainer after you start the geny. Mine did the same thing, just need a good prime, However be very careful to not let the hose run if the engine stops, it might back feed to engine.

[SpiritBear]

Originally Posted by MikkiDuda

Might sound like a stupid question, but is the impeller spinning at the same rate with the pump shaft and the engine? Might be a sheared key. Also, is the cam inside the pump in the right place?

Another stupid question because I’ve made this mistake myself: was the new impeller installed with the blades bent in the correct direction?

[Mr O]

Similar 60

What genset make/model? Some genders have an anode on the head that can get clogged with salt sludge. Not sure that’s what is causing your genset cooling system not to flow using the mechanical pump if flow is ok with electric pump. That said, it can’t hurt to run some scale remover thru the system and test flow with mechanical pump again.

The Fisher Panda 4K on my boat is located on the opposite side of the main engine and its raw water pump is on the far side on the bottom making it impossible to access unless I remove contents of cockpit locker, remove microwave enclosure, move microwave forward, remove locker bottom hatch and then go head-down into the engine room!��
So, I am interested in a solution to avoid the contortions and bruises. How did you find the correct size & flow rate of the pump? How did you wire the pump? Trigger relay to switch pump on? Source of the pump? Is the pump explosion proof?

Thanks for bringing up this conversation.

[Simi 60]

Originally Posted by SpiritBear

Another stupid question because I’ve made this mistake myself: was the new impeller installed with the blades bent in the correct direction?

Doesn't matter, they reset in the correct direction as soon as the motor turns over.
Try it yourself next time you change an impeller.

[Simi 60]

Originally Posted by Mr O

Similar 60

What genset make/model?.

Doesn't matter.
Its not a genset issue its a pump issue

Some genders have an anode on the head that can get clogged with salt sludge. Not sure that’s what is causing your genset cooling system not to flow using the mechanical pump if flow is ok with electric pump. That said, it can’t hurt to run some scale remover thru the system and test flow with mechanical pump again.

If you had read the post you would see I pulled off the HE in December and again a couple of days ago.
The HE is not the problem, its the pump.

How did you find the correct size & flow rate of the pump?

Pump specs and maths

How did you wire the pump? Trigger relay to switch pump on? Source of the pump? Is the pump explosion proof?

If you read the linked post you will see how it will be done.

For now in the short term while there is no sun/solar here I have ran an extension lead from the pump in the ER to a powerpoint near the genset start.
Start genset > turn on pump.
Turn off pump > shutdown genset

As soon as we get sun/solar again I will install and wire it in permantly.

[Apollo366]

How much water comes out of your genset exhaust? Small, nirn, goodly amount?

I had a similar prob & it was the exch cooling jacket & elbow being clogged with carbon buildup.

Capt Wayne