Raw water strainer

[novice04]

I'm in need of your help - again!
I'm thinking of changing the cooling raw water strainer on my VP MD3B. However, the existing setup is somewhat strange - the ID of the inlet hose from the thru hull to strainer is considerably larger than the output from strainer to engine (roughly 3cm input - 2cm output)! I can't see if there are any "reductions" on the strainer water hose connections for sleeving the hoses up/down. The strainer looks like Vetus plastic water strainer, but is old and covered in dirt/rust.
The question is - is there any reason for this difference? Obviously, more water is coming to the strainer than going to the engine. Why?And how to proceed with replacement - available strainers have only one size of in/out connectors??
Thank you in advance!

 

[Poignard]

ASAP Supplies Ltd, of Beccles, and probably most chandlers sell a stepped plastic adaptor that gets round the problem of different diameter hoses. I think Plastimo make them.

 

[ParaHandy]

If it is a vetus you might like to consider just changing the lid. Its the lid which will fail before the body of the strainer and you can get the lid plus o ring seal quite easily.

The difference in diameter might be explained by what the outlet of the strainer is attached to?

 

[TheBoatman]

The first quetion is "why do you want to change it"?

Secondly don't worry about the hose difference because some boat builders always fitted a larger hose from the sea cock to the strainer so that there was more water available to the pump than it could handle.

If you do chamge it then reducers are available to fit.

Peter.

 

[novice04]

Thank you all! Just what I was after.
As to "why..." question, I'm tempted to say "because I can (I think)!" - which is opposite to so many things that "I can't" that it almost serves as a reason in itself.
But, seriosly, it's because the thing is so dirty and covered in rust from the bolt and the wing-nut that I can't see what's happening inside, and because I'll have to break it in case I really MUST change it. I'll get a spare one + fittings and maybe just keep it on the boat for the time being.

 

[pampas]

bigger diameters are to reduce suction pressure on pump there for making it more efficient, common practice.