Strainer empty, is this normal?

[RichardS]

The only place where that can be is the top cover of the strainer, as that is the only bit above the waterline.

Therefore examine the cover for any cracks etc, replace the seal (and the seal on the retaining nut if it's the type with a retaining nut), coating the seal(s) with Vaseline or similar.

Avoid over tightening the cover, or its retaining nut, as that is a well known cause of leaks.

I would normally agree ..... but the OP has bought a brand new strainer, lid and rubber ring so surely that one can't have a leak as well.

However, as I said this morning, the air must be getting in at the strainer or upstream of it so a clear tube from strainer to seacock has to be the obvious next diagnostic stage to see if air is being sucked in through or around the seacock. I know that sounds ridiculous if there is no water leak when the engine in not running but, getting desperate now, perhaps some kind of leak on the seacock which is covered by a flap of sealant which is acting like a one-way valve!

Richard

 

[Jokani]

Strange.It stands to reason that if you had a vacuum in the strainer it would be filled by seawater.Maybe what you have is positive pressure that's not allowing water to come in?

Yes, you and Vic were both right on this one , it cannot be a vacuum.

 

[Jokani]

I would normally agree ..... but the OP has bought a brand new strainer, lid and rubber ring so surely that one can't have a leak as well.

However, as I said this morning, the air must be getting in at the strainer or upstream of it so a clear tube from strainer to seacock has to be the obvious next diagnostic stage to see if air is being sucked in through or around the seacock. I know that sounds ridiculous if there is no water leak when the engine in not running but, getting desperate now, perhaps some kind of leak on the seacock which is covered by a flap of sealant which is acting like a one-way valve!

Richard

Thanks Richard, I have some clear reinforced suction tubing (cheaper than the current sanitation pipe I am using) on order and will try this at the weekend.

 

[Kylora]

But the OP's strainer is full until he starts the engine so he doesn't need the kettle trick.

Richard

I was responding to the comments made by Pagetslady, rather than the Op.

Ash

 

[Jokani]

Many thanks for all the helpful comments.

I had already fitted fitted a new clear strainer lid and seal, so I was not expecting the vaseline solution to work.

But as it was the simplest of the list of possible solutions I had, I thought I would try that first.

Happy to say, I think it worked.

Before starting the strainer was empty and the seacock closed, when I removed the strainer lid, the strainer filled from the pump side which I thought was strange as I thought the pump formed a seal at that end?

Any way, open seacock, a liberal smear of vaseline around the seal and started her up. Full throttle alongside the pontoon for 25 to 30 minutes, strainer still full!

One happy camper!

When I left the strainer was still full, hoping that is still the case when I go this weekend.

Thanks for all your help!

 

[RichardS]

Many thanks for all the helpful comments.

I had already fitted fitted a new clear strainer lid and seal, so I was not expecting the vaseline solution to work.

But as it was the simplest of the list of possible solutions I had, I thought I would try that first.

Happy to say, I think it worked.

Before starting the strainer was empty and the seacock closed, when I removed the strainer lid, the strainer filled from the pump side which I thought was strange as I thought the pump formed a seal at that end?

Any way, open seacock, a liberal smear of vaseline around the seal and started her up. Full throttle alongside the pontoon for 25 to 30 minutes, strainer still full!

One happy camper!

When I left the strainer was still full, hoping that is still the case when I go this weekend.

Thanks for all your help!

As ensuring that the strainer lid was properly sealed was the first advice given I still don't understand why that didn't work with the old strainer?

Richard

 

[Jokani]

Hi Richard, yep my fault, I replaced the strainer lid and seal and couldn't see how that could leak, and it was only when I was running out of options that I tried the vaseline, just to be 100% on the seal. It is true if I had tried this originally I could have save some time, money and posts.

 

[RichardS]

Hi Richard, yep my fault, I replaced the strainer lid and seal and couldn't see how that could leak, and it was only when I was running out of options that I tried the vaseline, just to be 100% on the seal. It is true if I had tried this originally I could have save some time, money and posts.

Don't worry about it. Hopefully these threads will be available for many years so you can be sure that your thread will help many others over the years.

A small point but vaseline is not the best solution although it is cheap so it's useful for isolating the problem. However, now you know what the problem is, you would be advised to wipe off the vaseline and replace it with silicone grease. Not only does vaseline dry out and stop sealing after a while but it also degrades some kinds of synthetic rubber over time.

Richard

 

[30boat]

Don't worry about it. Hopefully these threads will be available for many years so you can be sure that your thread will help many others over the years.

A small point but vaseline is not the best solution although it is cheap so it's useful for isolating the problem. However, now you know what the problem is, you would be advised to wipe off the vaseline and replace it with silicone grease. Not only does vaseline dry out and stop sealing after a while but it also degrades some kinds of synthetic rubber over time.

Richard

That's a good tip.A strainer in good shape shouldn't need grease though.

 

[Jokani]

A small point but vaseline is not the best solution although it is cheap so it's useful for isolating the problem. However, now you know what the problem is, you would be advised to wipe off the vaseline and replace it with silicone grease. Not only does vaseline dry out and stop sealing after a while but it also degrades some kinds of synthetic rubber over time.

Richard

Thanks again For the advice, will get that swap the vaseliens for silicone grease over this weekend. I agree with 30boat, it shouldn't need it, the strainer was new in June 2014, but is seems to have done the job, and I'm not keen on spending another £70 on a new strainer just yet.

 

[WF36]

A similar issue with my VP D1-30, ever since I have changed the impeller I have to backfeed the strainer with water and start the engine with the seacock closed to get it to pump water, once running is fine.

However after the boat has healed over I am back to square one again.
No leaks etc. Any thoughts?

 

[RichardS]

A similar issue with my VP D1-30, ever since I have changed the impeller I have to backfeed the strainer with water and start the engine with the seacock closed to get it to pump water, once running is fine.

However after the boat has healed over I am back to square one again.
No leaks etc. Any thoughts?

Non-self priming problems with an impeller pump can usually only be attributable to the fact that the impeller cannot pump water quickly enough. This is nearly always due to a) the pump itself not working efficiently enough due to too much clearance in the impeller or pump body or b) air getting into the system somewhere in the pump or upstream of it which means that the pump cannot develop sufficient "suction" to draw water up from sea level.

If the problems only started when you changed the impeller and you're sure that it is the correct impeller, then remove it and liberally smear it and the inside of the pump housing including the cam with silicone grease. If it then starts self-priming properly, the answer is within the pump itself. in that event, I would start by reinstalling the old impeller and if that works OK then something is not right with the new impeller or its fitment.

Richard

 

[WF36]

Non-self priming problems with an impeller pump can usually only be attributable to the fact that the impeller cannot pump water quickly enough. This is nearly always due to a) the pump itself not working efficiently enough due to too much clearance in the impeller or pump body or b) air getting into the system somewhere in the pump or upstream of it which means that the pump cannot develop sufficient "suction" to draw water up from sea level.

If the problems only started when you changed the impeller and you're sure that it is the correct impeller, then remove it and liberally smear it and the inside of the pump housing including the cam with silicone grease. If it then starts self-priming properly, the answer is within the pump itself. in that event, I would start by reinstalling the old impeller and if that works OK then something is not right with the new impeller or its fitment.

Richard

Thanks Richard, it wasn’t an OEM one. I have just reinstalled the old OEM one and will report back with my findings when I next go for a sail!

 

[KAM]

I'm having similar issues again this season. The new impeller doesent seem to work as well as the old one which had done at least 500 hours. It was purchased from a reputable supplier and appears to be genuine. Pump manufacturers spec says " a dry pump can lift water up to as much as 3 metres". There are mentions of impeller material changes in the manufacturers spec but seem to remember coming across this several years ago last time I had problems. Been through all the above checks. The only conclusion I can come to is it's a bit of a tall order to expect a moulded plastic housing and cover to provide a decent seal with an O ring. O rings shouldn't need grease to seal. I suspect the grease is acting on the threads and improving the clamping force on the ring.

 

[Jamie Dundee]

The new impeller doesent seem to work as well as the old one which had done at least 500 hours.

That sounds as if the old impeller has worn to a good fit with a worn pump.

 

[KAM]

Not possible. Pump housing is good it's been dimensionally checked several times. Cover plates seem to be the weak point so I carry a spare. These are polished flat each season and O ring replaced. Yanmar quote a life of 1000 hours or 4 years for the impeller. Thinking back several years installing a new impeller has previously caused problems. Dimensional checks didn't reveal any measurable differences between the old and new impeller at the time. Seemed worse this year. Took a washing up bowl full of water instead of a mug full to get it primed. Its almost as if the properties of the impeller change once its been in service for some time. The last great boating mystery!