Locating seawater strainer

Michael Abramson · Post by **Michael Abramson** » Sep 13th, '07, 00:20

I am adding a sea water strainer after dealing with overheating in my Volvo MD7A. After doing the engine work, it seemed like age and corrosion were the culprits, rather than ingested matter. But the strainer will add a layer of protection in any event.

Having not had one before, I am curious where most people have these mounted. I don't really think I'll need to access it often, so I would probably locate it aft of the engine, but would then have to go through the cockpit locker and a removable panel to service it. Plenty of space for it, just hard to get to. One negative is I could not simultaneously reach the engine seacock from this position.

If I am likely to need to open and clean the strainer frequently, then I need to find a spot for it in the front of the engine bay, although this area is already crowded.

Any suggestions on placement? Thanks.

Ron M. · Post by **Ron M.** » Sep 13th, '07, 07:02

Usually installed right after the engine seawater intake. Some advise to get it above the waterline so it can be opened and cleaned without water flowing from it, but if you close the sea cock it accomplishes the same thing.
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rtbates · Post by **rtbates** » Sep 13th, '07, 09:11

Seraph, our 25D, has her strainer in the bilge. It's mounted on a board on the side toward the top. Works great as any water from taking it apart goes where it needs to, directly. Since it's below the waterline I simply close the seacock to prevent free flow.

Zeida · Post by **Zeida** » Sep 13th, '07, 21:26

[img]http://www.imagestation.com/picture/sra ... 247514.jpg[/img]
You can see my raw water strainer located at the bottom, right frame, with the white plastic cap. You do need to clean it often. The hose leading to it comes directly from the raw water seacock and from the strainer, continues up to the raw water pump. It is rather cluttered there for me too, but I had to make room for it regardless. I guess it depends where in your engine compartment you have the raw water seacock and how the hoses are routed to your raw water pump. All of them should be close together, but you need to access the strainer easily.

Michael Abramson · Post by **Michael Abramson** » Sep 14th, '07, 00:11

It does look like I need to find a way to mount it at the front of the engine, instead of a more remote location. My engine seacock is on the same location as Zeida's raw water filter, and my large cockpit drain hoses also cross in front of the engine, so my space is very congested. Perhaps alongside the engine, just behind the alternator will work. Then I can reach both the seacock and the strainer from the same access. The feedback about needing to clean it often is very helpful, that was the main thing I did not know. Thanks again.

seadawg · Post by **seadawg** » Sep 15th, '07, 09:46

You know, I installed a Groco model seawater strainer in the engine compartment all the time wondering if I did the right thing. Sense there is a strainer already outside on the hull. After five months of use there is very little in the basket, just a few flects of paint from the bottom job I did. I am considering removing it but am in no particular hurry to do so. Any experiences out there or thoughts?

Michael Abramson · Post by **Michael Abramson** » Sep 15th, '07, 10:04

If you sail where it is usually deep water, it may never pick up anything significant. I am often in shallow water with a sandy bottom, so I think I will go ahead with the install and then monitor
if it is doing anything.

Did you install yours below the water line, so it is under pressure when the seacock is open?

Off to the boat now to complete this job.

SeaBelle · Post by **SeaBelle** » Sep 15th, '07, 11:04

Mike,

Just returned from a 6 day cruise that had an unfortunate beginning. We planned to leave Sunday night after I returned from a family wedding. The crew waited, I rushed, and finally we set off. BUT before we were half out of the harbor we noticed white exhaust smoke and temp about to go into the red zone so we returned to the dock. We found quite a bit of vegetation in the strainer but cleaning it didn't solve the problem. Since our 1st leg was 160nm we were reluctant to leave and waited overnight for the yard to open.

The culprit was that the hose from the seacock to the strainer was also obstructed with vegetation. Restricted raw water flow flow caused the engine to overheat and 'boil' the raw water. The white smoke was raw water vapor.

Lessons learned:

1. Don't only look for raw water flowing; be sure the flow rate is normal.
2. Check engine temperature as if your engine's life depends on it; it does.
3. Check your raw water strainer frequently.

The 15 hour delay demanded that we replan our trip and I missed taking the captain to Rogue I., one of my favorite places. The good news is that we had a brilliant trip.

(BTW, be advised there are 2 can 5's on the approach to Matinicus Harbor. I almost scratched my head through. In Matinicus, moored next to us was a CD30 ketch with 'Just Married' on the hull, taped with each letter a different color. The newlyweds were from Brunswick, ME. It reminded me of Eric Hiscock's observation, "The only way to get a good crew is to marry one.")

seadawg · Post by **seadawg** » Sep 15th, '07, 13:01

Michael, I did install it above the water line but as rtbates mentioned it is not real important if you have a seacock. The Groco has a glass bowl and a location where you can see it from the side and get the internal basket in and out is handy. Neither of my strainers will keep fine grains of sand out however.

Ron M. · Post by **Ron M.** » Sep 15th, '07, 14:57

Seadog,
An added bit of insurance........I used the Groco also and although it has of yet not captured anything significant I'm glad I installed it.

Michael Abramson · Post by **Michael Abramson** » Sep 15th, '07, 17:27

I also have the Groco 750. I see the mfr recommends it is placed above the water line, but I don't really understand that. Perhaps so it won't flood the boat if the top is left loose while the seacock is open? Can't the high position lead to loss of water flow under some conditions? I realize I won't be heeling much if motor sailing, but I think my intake is only about a foot below the waterline. How do I tell where the WL is from inside the hull?

I had to get new fittings to revise the hose runs more cleanly, so back to the project tomorrow.

Thanks for all the contributions.

seadawg · Post by **seadawg** » Sep 15th, '07, 19:52

Michael, you can find the water line easy by connecting your hose to the seacock, open the seacock and drop the hose slowly until water begins to flow out of the end of the hose. You are right, it is very important to have good quality hoses and good clamps in the system, otherwise the engine water pump can suck air denying the engine of cooling water. If you are careful about the location of the strainer, later if need be you can disconnect the hoses and lift it off its mount to give you better access to other areas.

rtbates · Post by **rtbates** » Sep 17th, '07, 08:31

Michael Abramson wrote:I also have the Groco 750. I see the mfr recommends it is placed above the water line, but I don't really understand that. Perhaps so it won't flood the boat if the top is left loose while the seacock is open? Can't the high position lead to loss of water flow under some conditions? I realize I won't be heeling much if motor sailing, but I think my intake is only about a foot below the waterline. How do I tell where the WL is from inside the hull?

I had to get new fittings to revise the hose runs more cleanly, so back to the project tomorrow.

Thanks for all the contributions.

Michael:

Yes it can. The 'problem' is air which rises of course. Any air will have a much harder time finding a route up and out if it has to go through the filter system. Placed below the water line the water pressure will force water into the filter, displacing the air, rather than relying on the pumps suction to pull water in hence displacing the air. Those little pumps don't like to fight much head, especially if there's air in the line.

Michael Abramson · Post by **Michael Abramson** » Sep 17th, '07, 10:18

I went with the collective wisdom of those who mounted the strainer below the water line, despite Groco's suggestion to the contrary. I think having water pressure all the way to the engine's tiny pump is a good plan. I won't be servicing the strainer without the seacock being closed, so the only risk is leaving the cover of the strainer loose. That is easy to check when opening the engine seacock.

I'll add an extra one of the big o-rings in the cover to my spares selection and should be good to go.

If anyone is servicing a Volvo MD7A's water pump, I have a few suggestions that may help. I cut out some of the metal piping (which was corroding badly) and replaced it with rubber pre-shaped hoses from Pep Boys. I also replaced the 2 mounting screws with metric allen head screws for much easier future removal/replacement, the original ones were impossible.

I had very good luck finding most of the parts I needed for exhaust manifold removal, water pump rebuilding, and the Groco strainer on eBay for fractions of the market prices. The rest of what I needed I got from Marine Parts Express, who has good service and moderate pricing, and a few more things from West Marine.

Dean Abramson · Post by **Dean Abramson** » Sep 18th, '07, 07:46

Hey Bro,

Ours is in the cabinet under the sink in the head, which (the cabinet) is adjacent to the engine compartment. The engine water seacock is there too. The filter is below the water line.

Maybe Groco thinks it's safer above the WL because of the glass bowl; on the theory that you may also have left a heavy wrench or something lying in there, which could shift and crack the glass. I dunno.

Dean

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