Whale MK5 pump - advice ?

[Delfini]

The boat has been ashore for most of 2020 having a new deck fitted and Im now slowly going through the various systems and fixing things that stopped working (I believe mostly as a result of being ashore for so long) as I go - a few days ago I noticed the alarm on my Holding tank was showing 3/4 full and having checked the diverter valve in the aft heads I noticed the waste had been diverted to the tank rather than is usual, to sea - I tried the manual Whale pump to reduce the level but although the handle was moving fine it didn’t seem there was any liquid involved - even though this pump is self priming it sounded like it was pumping air so I thought it best to fill the tank and then pump from there - I put a load of sea water down the toilet and sure enough the theory worked but instead of the manually pumped waste water going to sea it started coming out of the front of the pump mounted behind a bulkhead in the aft heads - seemed like from where the handle locates in the pump

I haven’t started to take it apart yet but all the exploded views I can find online don’t show how the handle socket locates and how it then pumps the diaphragm and how liquid might escape through the handle socket - the service kits offer a diaphragm and inlet and outlet valves but is that what I am likely to need ?

Any advice appreciated

 

[earlybird]

Seems like the diaphragm is split. A service kit is needed. Best if the pump is dismounted.

 

[Gary Fox]

Get a rebuild kit, as above ^^ you have to remove the pump, scrape off all the dubious corrosion and crusty 'matter', so the new rubber can make a good seal on clean alloy.
Enjoy

 

[Delfini]

Seems like the diaphragm is split. A service kit is needed. Best if the pump is dismounted.

.. thanks - are you saying there is a path from the pump diaphragm chamber through the pump handle socket which would explain the symptoms - if that’s the case I believe its possible to replace the diaphragm by removing the top plate only

 

[earlybird]

Yes it will leak past the handle. When dismantled you will find the pump internals coated in hard scale. Dismantling the pump on the bench is best IMO.

 

[VicS]

The boat has been a
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I haven’t started to take it apart yet but all the exploded views I can find online don’t show how the handle socket locates and how it then pumps the diaphragm and how liquid might escape through the handle socket - the service kits offer a diaphragm and inlet and outlet valves but is that what I am likely to need ?

Any advice appreciated

Perhaps the diagram here helps

https://www.whalepumps.com/marine/s...ce-library/ExplodedView/MBP_Mk5_Universal.pdf

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[Delfini]

Perhaps the diagram here helps

https://www.whalepumps.com/marine/s...ce-library/ExplodedView/MBP_Mk5_Universal.pdf

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Thanks for that - looks like the pump handle attaches to the pivot arm in the picture - in which case if the diaphragm is split there would be a path through - Ill get the kit and brace myself for the nastiness within !

 

[rogerthebodger]

I've had the same issue with my Henderson pump. I found build up on the inlet flap valve preventing the NRV closing correctly.

I stripped it down and cleared the calcium buildup by dunking in vinegar for a day or 3

I did have the diaphragm centre screw nut break then allowed leakage replacing the nut solved that issue.

 

[Topcat47]

The kit should come with replacements for the inlet and outlet "Valves". It really is easier to do the job on the bench. You can replace the diaphragm in situ in an emergency but it really is best to have the whole thing apart, thoroughly clean it, then replace the "consumables". While it's not essential, I always run a small bead of silicone around the diaphragm where it mates with the pump body (Fernox LSX from my local plumber's merchant:- it's a small tube and not requiring a gun to apply). No problems with ether my double acting Henderson or my Whale Mk5 since last done, but I do always keep a complete set for the Henderson on board (the whale pump is a single acting so in an emergency, I can do either).

 

[Delfini]

Today I bought the kit and proceeded to remove the 8 x screws holding the top plate to the main body - as predicted the diaphragm was split. The top section contains the inlet and outlet valves so I left the main body attached to the boat and cleaned everything before replacing the crusty valves and the diaphragm - thanks to all

 

[doug748]

I bought a new Mk5 two years ago and the diaphragm split in no time at all, so keep an eye on it. As I pointed out to them, the one in the heads is going strong at 25 years!