3gm30f water pump plan.

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IanCC

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In view of the ludicrous replacement price of these pumps at what point does one rebuild on a preventative basis?
Mine isn't pretty but doesn't leak. Will it ruin a fortnight pottering around the Scottish west coast if i don't carry a spare.? I would like to think you could let them drip for a few hours before they sieze or self destruct. Thoughts?
 
If something is obviously failing, I'd always repair/replace it before it causes a problem. In your situation, I'd replace the seals and bearings either with new ones from ASAP or better still with generic ones from a local supplier if you have one. Remember to use seals with stainless springs or you'll be doing it again quite soon.
The replacement process is straightforward using a suitable sized socket and large hammer if you haven't got a decent vice.
Hopefully you won't find the shaft excessively worn as a replacement is costly.
 
Best carry a whole spare
And the drifts, vice , seals and bearings to change out the failed parts in the cockpit , having spent 12minutes swapping out the failed pump from its slightly awkward reversed location . But all perfectly doable for a cruising boat
But does the OP want to carry tools , spares AND a £300 Worth of spare pump that might never be used ?
Decisions decisions
( for the record I’ve repaired mine once on board without undue difficulty having nursed it dripping for a few hours , would have preferred to carry a rebuilt s/h pump as well)
Sorry, long winded response ?
 
Having had two raw water pumps and two coolant pumps fail I now carry a spare of each for my 3YM 30
Experiance says don’t over tighten the drive belts and if there is any leak then sort it promptly. If it doesn’t slip the belt is tight enough.
 
I refurbished mine a few years ago with bearings and a seal from Polar Bearings in Colchester. I thought I had to repeat the exercise last year when it leaked again. When removing the pump I found that the lower jubilee clip had failed so replaced both.???
 
ghostlymoron said:
If something is obviously failing, I'd always repair/replace it before it causes a problem. In your situation, I'd replace the seals and bearings either with new ones from ASAP or better still with generic ones from a local supplier if you have one. Remember to use seals with stainless springs or you'll be doing it again quite soon.
The replacement process is straightforward using a suitable sized socket and large hammer if you haven't got a decent vice.
Hopefully you won't find the shaft excessively worn as a replacement is costly.
Click to expand...
How do you use a vice for this? I am sure it is a dumb question.
 
It looks old and tatty. But it probably did 5 years ago. You say the telltale hole gives warning as opposed to telling you it's finished. I guess that is what i am asking really. How much notice do you get, how long from drip to failure?Hopefully off for fortnight sailing next weekend and don't want to rebuild next week and don't want to buy spare if a few drips, if they occur, don't matter. Haven't rebuilt in previous weeks as have been concentrating on getting engine reliable and my learning curve hadn't quite reached the water pump.
 
If it ain’t broke don’t fix it. I have the same Johnson pump on a 3gm on the sunny (is today) west coast. When mine started to leak a good few years ago, I had a good priced option of a new one. Still have the old one fixed with stainless seals and bearings from an Ayrshire branch of a company, £25 odd inc postage if I remember for the three seals and bearings and not too difficult a job. Can email pics and details of bearings if needed..

As to the leak, it was there for a while before I fixed it. It will pump but just leak a tiny bit.
 
ctva said:
If it ain’t broke don’t fix it. I have the same Johnson pump on a 3gm on the sunny (is today) west coast. When mine started to leak a good few years ago, I had a good priced option of a new one. Still have the old one fixed with stainless seals and bearings from an Ayrshire branch of a company, £25 odd inc postage if I remember for the three seals and bearings and not too difficult a job. Can email pics and details of bearings if needed..

As to the leak, it was there for a while before I fixed it. It will pump but just leak a tiny bit.
Click to expand...
You are a star. Thank you. Pics and details would be fabulous. No worries if you can't find them.
 
Will do from the home pc but not today as the G&T is going down well in the Black Isles… ?
 
It will not fail precipitously. When the seal starts to leak as indicated by the weep-hole drip, water will tend to weep along the shaft towards the bearings. There should be a slinger disk on the shaft that will fling most of the water off, but eventually some water will get to the bearings which will then gradually be affected over a period of months, not days or weeks. What you might notice before actual bearing failure is occasional difficulty in priming the pump due to the worn seal allowing air to be sucked in. This showed up on mine when motor-sailing in conditions which caused the CW through-hull to be repeatedly out of the water, eventually leading to the engine temperature alarm going off. After dropping the sail to keep the boat flatter, it took quite a while for the pump to prime and resume pumping even with a new impeller put in. But I got home ok.

It's quite straightforward to reco the pump. Don't fret about wear marks on the shaft from the seal lip - you can easily polish them out with emery paper. Start with coarse and work up to a mirror finish with progressively finer grades.
If you do it yourself you'll save heaps of money and gain the confidence of understanding how it works and how to fix it. Mine is going strong over 500 hours run time since my DIY refurb.

Cheers, Graeme
 
Last edited:
zulloboy said:
It will not fail precipitously. When the seal starts to leak as indicated by the weep-hole drip, water will tend to weep along the shaft towards the bearings. There should be a slinger disk on the shaft that will fling most of the water off, but eventually some water will get to the bearings which will then gradually be affected over a period of months, not days or weeks. What you might notice before actual bearing failure is occasional difficulty in priming the pump due to the worn seal allowing air to be sucked in. This showed up on mine when motor-sailing in conditions which caused the CW through-hull to be repeatedly out of the water, eventually leading to the engine temperature alarm going off. After dropping the sail to keep the boat flatter, it took quite a while for the pump to prime and resume pumping even with a new impeller put in. But I got home ok.

It's quite straightforward to reco the pump. Don't fret about wear marks on the shaft from the seal lip - you can easily polish them out with emery paper. Start with coarse and work up to a mirror finish with progressively finer grades.
If you do it yourself you'll save heaps of money and gain the confidence of understanding how it works and how to fix it. Mine is going strong over 500 hours run time since my DIY refurb.

Cheers, Graeme
Click to expand...
Thank you for taking the time to reply to my thread. That is great. I will keep an eye on it and refurb it later in the year.
 
No. If the pump is not leaking, then it'll likely survive your planned cruise even if it begins to drip on day one. We were once obliged to travel from the north Caribbean to the USA in that situation, I'd guess we put 100+ hours on that dripping pump. The drip had become a dribble by the time we could fix it, but no show stopping problem
 
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