Raw Water (After the Pump) Strainer

[a64pilot]

There has been on and off discussion of installing a strainer after the water pump">raw water pump, it’s primary purpose is to catch bits and pieces of a pump impeller should one come apart. I’ve always been meaning to but never got a round tuit. Anyway on our way to the Bahamas on our crossing I had a pump come apart, which of course ended up requiring disassembly of the heat exchanger to get the bits and pieces out, luckily I did not have one of the bits clog an exhaust elbow where the water flows into the exhaust, I’ve heard of that happening but by luck it didn’t to me.
Anyway I removed the stock Yanmar hose on my 4JHE which as it was 32 years old it tore on removal, it was age hardened. There are three deep threaded bosses on the side of the heat ex to mount something I’m sure that aren’t used in my installation, I bought an SS angle off of Amazon and a strainer on Amazon and mounted it there. Stock there is a tube that mounts on the water exhaust hose and routes water to the oil cooler, it has no other function and nothing taps into it, it’s held to the heat ex with one 8 mm bolt. I could have used this bolt to mount the strainer, it’s the perfect size.
I had to remove this tube to get the hoses in without them kinking.
It works fine so far, and the next impeller failure all I will have to do is unscrew the strainer cup and remove the pieces, of course I’ll have to put a new impeller in the pump too.

[Compass790]

I did the same thing as I was prompted to do it by finding impeller bits in our raw water cooled engines cooling passages when I rebuilt it.
Good mod I reckon
I did find however the mesh screen was too fine & had to drill ( frm memory) 6mm holes in it as it it got clogged with little jellys & various forms of marine life.

As a bonus the impeller doesn't want to fail now

[a64pilot]

The screen is a lot finer than I wanted, but it was all I could find.
I can as you did always drill it full of holes. I guess I could bend a piece of screen wire to fit too.

[HopCar]

Nice job!

I think Groco might make a basket out of plastic that will fit that strainer. It would have larger openings. It would be for their WSB-P series strainer. Several companies seem to sell that same strainer under their name.
Sherwood, Shurflo and Groco all sell strainers that look like that. I suspect they all come out of the same factory in China.

[model 10]

We have been cruising for a while and I have not seen much more than some sea weed in the primary strainer and it was a total pain in the ass to clean from the bronze 19'th century water strainer. I've switched to a strainer for a big boat gen set that has a fine screen and is easy to clean.
I've never lost an impeller vane. I've seen cracks but never a total failure.

[Jetx]

Originally Posted by HopCar

Several companies seem to sell that same strainer under their name. Sherwood, Shurflo and Groco all sell strainers that look like that. I suspect they all come out of the same factory in China.

Agreed. In the aircon strainers on our previous boat, I used (coarser) Sherwood 20-mesh stainless strainer screens... although the strainer bodies were Shurflo and Forespar branded. Dimensions of the Sherwood screens were identical to the original (finer) Shurflo and Forespar screens, so of course they fit perfectly.

For these small strainers, they're cheap enough to just buy a few different brands/types and try them to see if they fit your strainer.

[deblen]

Originally Posted by HopCar

Nice job!

I think Groco might make a basket out of plastic that will fit that strainer. It would have larger openings. It would be for their WSB-P series strainer. Several companies seem to sell that same strainer under their name.
Sherwood, Shurflo and Groco all sell strainers that look like that. I suspect they all come out of the same factory in China.

I installed one of the above (brand?) plastic strainers between pump outlet & heat exchanger several years ago after having to clean impeller bits & other fines out of HX. In a rush & left strainer laying with hoses along edge of eng. space.Still there.I think I checked the filter a couple times after install & pristine. Just put it on this fall's todo list.
I also have a bronze Groco pre-RW pump filter,so I doubt if any "seawater" crap makes it to this second filter.

Cleaning a Volvo 2003 HX once was all it took to convince me this second filter is well worth the $50-$75 cost of it.. Highly recommended/ Len

[Sandydog]

This is a very good topic. I believe I have seen responses in the past. My boat only has a clam shell type strainer on the hull exterior. The boat has been operated many years this way with no issues. I think if you change your impeller regularly, then having a mesh screen could really be problematic. The system is designed to chew up and spit up the small organisms, etc. that make it through the clam shell.

[a64pilot]

This is the strainer, think a groco plastic strainer will fit?
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[a64pilot]

Originally Posted by Ecos

I've never lost an impeller vane. I've seen cracks but never a total failure.

I never have either, however I tried an off brand impeller, cool pumps or something, and less than 10 hours I could tell the exhaust note had changed and water flow drastically reduced, motor didn’t overheat, but I run at less than 2000 usually though.
Stopped at anchor for the night and pulled the impeller and all but one vane was gone I believe. Put in an OEM impeller and water flow got better but you could tell there was restriction still, took heat ex cap off and all the missing canes were there in the cap right where there was a sharp turn, that caught the blades.

I had heard here of people installing a filter downstream of the pump and I decided to then.

[andrzej0nl1ne]

I did something similar on my yanmar 3gm30f few years ago, and it has been effective for me.

I was concerned about water pressure so I used a bronze in line bypass strainer. It is robust but I cannot see strainer content. I have to open the bypass to check.

This year I also added quick connects between the strainer and the pump to simplify pump disconnect when charging the impeller. For the uninitiated, on the 3gm, the pump backplate is rear facing which complicates things. The connection hoses are also short, so each impeller check introduces radical bends in the hoses at common points. Good news is that the quick connects have held.

I'm curious if my pressure concerns are unwarranted, which would open the strainer to many more options.

[model 10]

[QUOTE=a64pilot;
I had heard here of people installing a filter downstream of the pump and I decided to then.[/QUOTE]

Makes great sense. I needed a pre filter and the only choice was a big filter kind of like yours. I found it at a store that sells stuff for big motor boats. I have rationalized that it's better for the pump than a strainer. 2 of them would be pretty cool, but the one was 850Q.

[Sandydog]

No filter needed. It will clog at the worst time. Boats for years had only the exterior filter. Maintain the intake system properly and you will have no issues.