Where can I source a 3/4" scoop intake strainer

[Ammonite]

I'm looking for one in DZR or Bronze and I'm not keen on the type that asap-supplies supply that requires you to drill extra holes in the hull to attach the strainer

Vetus do one but it's around £70. I can find loads in brass around the £20 mark (no good as the boat is in salt water) and also plenty in bronze in the US but it seems daft I can't find one here. Maybe I'm using the wrong search terms in Google ;-) Thanks

 

[David2452]

3/4" is a bit small for one of the one piece bronze ones but here's a suggestion, consider the smallest Gudi bronze one at 1" and fit a reducer, part # 2-70273 from Aquafax at about £35 retail, reducer part # 1-72152 in bronze about £8 retail.

 

[Tranona]

Why do you want an external strainer? It is not common to fit them these days as they are prone to blocking and restrict waterflow. That is the main reason why you are unable to find one. Normal practice now is to fit a strainer above the waterline, and if possible immediately above the seacock. This allows you both to clear away any weed etc in the cooling water - it gets trapped in the strainer basket, and to be able to clear any obstruction in the intake itself by rodding. The Vetus catalogue has a schematic of the common layout for engine water intakes.

 

[PCUK]

We use ASAP and don't drill any additional holes.

 

[Ammonite]

Thanks for the replies

Tranona - looking at page 60 in the online Vetus catalogue (typical installation) it looks like they use a scoop strainer as well as the basket type strainer (which is the setup I have). It definitely doesn't look like a ordinary skin fitting

What diagram are you referring to?

PCUK - having not seen the asap (Perco) version in the flesh I thought the strainer part will simply fall off if it wasn't screwed to the hull (on the basis that they also sell the strainer part separately). How is it attached to the threaded section of the fitting?

Thanks

 

[Pasarell]

Force 4 at Bursledon had them 3 weeks ago, but all their fittings seemed to be marked randomly as bronze or brass, many with hand written labels. I didn't feel at all comfortable they knew what they had, compounded when one of their long standing staff assured me brass was fine below water as "it is the most popular". Ended up buying Vetus parts.
I agree with the point about fitting a good water strainer internally rather than externally incidentally. Part of what I did was to change the old and inaccessible bronze strainer directly on the seacock to a new Vetus one that I could get at, fed by a clear reinforced 1m pipe from the seacock.

 

[Tranona]

Thanks for the replies

Tranona - looking at page 60 in the online Vetus catalogue (typical installation) it looks like they use a scoop strainer as well as the basket type strainer (which is the setup I have). It definitely doesn't look like a ordinary skin fitting

What diagram are you referring to?

That is the diagram. The skin fitting is just a schematic - it does not have to be a water scoop. That is redundant if you have a water strainer. Think you will find the recommendation from engine manufacturers now is a straight inlet (usually 3/4" for under 40hp engines) and an above waterline strainer. That is what is fitted as original equipment on most new boats.

Have a wander round boatyards now boats are out of the water and count the number that have external strainers! Don't think you will find many, particularly boats built in the last 20 years or so.

 

[David2452]

This is how I understand it, the strainer / scoop is more of a scoop than a strainer and just there to keep larger stuff out, the internal weed strainer does the job of filtering out the smaller stuff, most new boats at shows that I have seen have scoops, and mine, a large volume manufacturer only five years old certainly does. What I also understand (and certainly technically it makes sense) a plain flat type skin fitting with or without some kind of external strainer is subject to a venturi effect at anything over about 6 knots, making it harder for the water pump to prime and work.

 

[LadyInBed]

ASAP

 

[BabaYaga]

I have one of these:

http://www.seasea.se/Vatten/Vatten_Tillbehör/Rördetaljer/BORDSGENOMFÖRING_3_4_M_SIL

DZR brass through-hull and nylon strainer, which is held by two small s/s bolts to threaded holes in the external flange (= no extra holes in the hull).
May not be available in the UK, but by mail order from here.

As already pointed out: Does not replace internal strainer.

 

[Blue_mischief]

Sorry for a ...

... bit of thread drift. My boat has a an external scoop only and never had any problem with blockage. The strain slots face aft - I have been told this is the wrong way round. Can find nothing in any literature which supports or negates this. Anybody know?

 

[Leighb]

... bit of thread drift. My boat has a an external scoop only and never had any problem with blockage. The strain slots face aft - I have been told this is the wrong way round. Can find nothing in any literature which supports or negates this. Anybody know?

I have read somewhere, probably on this forum?, that they should definitely face aft.

The reason being that you don't want water to be forced into the intake when sailing, in theory it could pass through the pump and flood the engine.

I don't know if this is correct but it sort of makes sense.

Looked at another way, what reason might there be to have them face ahead. When the engine is running it is going to suck the water in fine anyway.

 

[pampas]

There are two types of external

(a) those that the slots face Aft

(B) those that the slots face Fwd.

In case (B) these have an internal protruding curved cast pipe and hence act as a true scoop. Hope that I have explained (Construction of "B") clearly.

 

[pappaecho]

That explains it! My internal strainer is never blocked. I have got an external strainer as well!
Different owners at different times