Is a sea water filter essential?

[Captain Crisp]

Hi, my raw water intake for cooling the engine doesn't have a filter... There is a grid on the outside of the sea-cock, but its apertures are much larger than a filter's would be.
Should I install one?
Thanks!
Crisp

 

[PCUK]

Yes, Yes, Yes!

 

[Easticks28]

YES YES YES !

 

[Old Harry]

And remove the grid too

 

[Clancy Moped]

As above, yes.

 

[Captain Crisp]

I'll take that as a 'Yes' then!
Many thanks,
Crisp

 

[bedouin]

I have a fine grid (well slots actually) outside and a filter on the intake.

I have never had to clean the filter so I assume it isn't doing much good.

 

[fisherman]

One day I cleaned the inlet seacock and forgot to replace the filter. Porthleven is particularly weedy after any weather and I sometimes had to clean it twice before getting outside.
The water didn't just slow, it stopped completely. Dry exhaust so the outlet showed instantly any shortfall. I had to strip the pipework, attached the two branch deckwash, one through the engine, the other backwards through the first oil cooler. When I got it running I briefly folded the hose going to the engine, to get a good squirt through the cooler.
For the next week I was cleaning up stinking finely chopped weed from the back of beyond in the engine room.
I was never able to decide between having an external grid and being able to rod the seacock through.

 

[vyv_cox]

It is a rule of thumb that all pumps should be protected by an upstream suction strainer. The strainer is a maintainable item, which rules out the grids on the outside of the seacock.

 

[michael_w]

All the grill does is provide a home for little wrigglers.

 

[vyv_cox]

This pic of a non-maintainable 'witches hat' strainer illustrates what can happen. OK, much bigger than we are talking about but quite amusing. When plant is commissioned strainers are inserted upstream of pumps and compressors as 'bolt catchers' in case debris has been inadvertently left in the pipework. Sometimes these strainers are inadvertently left in place, gradually blocking and eventually breaking up. I know of several cases in which the filter medium broke off completely, wrecking the equipment downstream.

 

[Allergy]

I'll take that as a 'Yes' then!
Many thanks,
Crisp

I have a Vetus raw water filter which does the job. But check similar types available on the market.

 

[Refueler]

My Perkins has the old typical sea intake ... with lever valve. The valve body extends vertically and inside is a mesh tube that provides rudimentary filtering before water passes up to system (raw water cooled). This seacock is a left over from the previous engine that had indirect heat exchanger. The mesh is not fine - in fact quite coarse.

I often have to pass through weed and grass in / out of my channel ... The mesh stops all weed and grass and in fact can reduce water flow seriously ...

Its dead easy clean .. close valve .. unscrew cap - lift out mesh ... slosh about in a bucket ... put back in screw cap backl on ... open valve ...

In over 20yrs I've had the boat - this has never been a problem and I have not experienced anything on the boat to convince fitting a finer filter system ..

I do admit though - I do not regulate my water flow .. its full on .. so any small stuff that might get through doesn't stand much chance !!

This is just after starting and fast idle throttle :

I let it stay high flow to ensure engine temps stays low to avoid creating crystaline formations in the passages ......... Perkins specifically warn about this and advise running raw systems cooler than indirect with the 4 series.

 

[alahol2]

Well worth trying to arrange the filter to be directly above the seacock. That way you can open the filter and rod straight through the seacock... as long as you haven't got a grid on the outside. I've been thankful for that arrangement on several occasions.

 

[Tandem]

michael_w's 'little wrigglers' cost me a couple of hours yesterday resolving lack of water flow. So, that external strainer's going to lose a bar or two when she comes out. But you definitely should have a maintainable strainer as per vyv_cox.

 

[fisherman]

In spite of all the regs on new FV construction they recently allowed a fit up which had a 90 deg bend on top of the inlet, before the valve, with all the expected consequences.

 

[prv]

My Perkins has the old typical sea intake ... with lever valve. The valve body extends vertically and inside is a mesh tube that provides rudimentary filtering before water passes up to system (raw water cooled). This seacock is a left over from the previous engine that had indirect heat exchanger. The mesh is not fine - in fact quite coarse.

In over 20yrs I've had the boat - this has never been a problem and I have not experienced anything on the boat to convince fitting a finer filter system ..

I know the type, I'd consider it a perfectly adequate strainer. I don't think anyone's advocating fitting some kind of very fine filter.

Our boat originally had no internal strainer, relying on just the size of the holes in the front of the saildrive leg. Each winter I tip a few small shells and scraps of weed out of the strainer basket I fitted - nowhere near a blockage, but I'm still glad they're not getting into the heat exchanger.

I have once had the toilet intake block completely within a few pumps, necessitating dismantling to remove quantities of weed, so there's always the possibility of sucking in more than the tiny scraps I normally find in the engine basket.

Pete

 

[Refueler]

I would think any finer strainer could lead to more problems than it cures ?

 

[pvb]

It's certainly worth having a strainer. One advantage of the remote-mounted Vetus/Volvo/Allpa strainers is that they retain some water to help prime the raw water pump.