A little problem with my sea strainer bowl

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rgano

rgano

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Oct 8, 2007
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USA
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FROLIC
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Mainship 30 Pilot II since 2015. GB-42 1986-2015. Former Unlimited Tonnage Master
I have been noticing a small dribble of water coming from the area of the drain plug on my generator's sea strainer whenever I shut the through hull valve while flushing the generator with shore water pressure with the boat in the lift. It did not leak while the boat was in the water. Access is restricted, and I cannot closely examine the unit. Today I connected the shore water at the tee downstream of the strainer and shut the seacock. Kapow! The photo shows the result. Apparently there was a stress crack of some sort which I finally got to show itself. New bowl on order.
 

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The strainers usual do no see high pressure but more of a vacuum that is. I would consider using a strainer that has a metal housing if you need to flush your system all the time. you are very lucky that it had happened during a water flush instead of during a cruise.
good luck,
 
Glad you caught it. Replacing the bowl will no doubt cure the problem for many years.
Always nice to have spare strainers and bowls and o’rings for the strainers on board. Save the delay time in ordering spares.
 
Do you think that crack developed from a freeze?
 
Yes, definitely not designed for 50 psi. While you could see pressures in the 1 to 3 psi range (each foot of water has about .5 psi) most installation are designed to have the strainer within a foot of sea level.

Ted
 
I can't speak to how the crack began, but the thickness of the plastic is impressive. With an alarmed bilge pump close by and the boat living in a lift when I am not running it, no real worries about it sinking the boat. Practice in the past was to leave the seacock open when flushing the genny because it was a brief time with no load which would not have given it cause to overheat. However, in recent months I have wanted to put a load on the genny while running for a half hour or more in the lift clear of the water; so I closed the seacock to ensure that too much shore water was not being lost through backflow via the through hull. I will just have to change my ways.:blush:

Yeah, the ruler came as a gift many, many years ago.
 
That's plastic ?? Good lord I wouldn't think plastic that thick would crack like that.
Maybe the drain was tightened too tight ?? Cain't imagine...
 
It looks like the crack originated at the drain penetration. Over tightening or no gasket or just an unfinished hole edge that allowed crack migration. Unless that is a tapered thread plug instead of a straight thread with gasket. That would be poor design.
 
Last edited:
Sink a boat?

I thought all the experienced guys here profess shutting seacocks at the dock and sufficient bilge pumping capacity to handle at least one major hose failure....

Certainly have heard many chime in on those safety points.

Everyone should take heed.
 
Both my generator and AC strainers are exactly the same type and they’re both somewhat below the waterline. I clean and check them carefully every fall but now I think I’ll be checking more often.

Ken
 
Rich
I had a similar occurance on one of the same ones on my 34 HT.
Crack was starting from the top flange on mine. I replaced it and carry a couple spares now. I did replace the main eng bowl also as it had the beginnings of some cracks on the top flange as well.
 
Yeah, the bowls on one of my engine strainers cracked a few years ago as well. I replaced them both and kept the intact one as a spare.

Mine didn't fail catastrophically though, just leaked. I wrapped it in rescue tape and put hose clamps around it. Got us through the trip.



Didn't think about my gen-set though.
 
This is probably going to be obvious once I see the answers, but can engine intake strainers be located above the waterline (presuming there is available "above the waterline" space in a given engine room)?

(Obviously the seacock is going to be below the waterline.)

It's been years since I've been on a boat with an inboard and that was sailing days, so we probably paid more attention to the rigging, etc. -- and just accepted the strainers the way they were installed. Plus there's heeling to consider.

Anyway, is it possible to mount engine intake strainers above the waterline on powerboats? And if so, what are the trade-offs? (Priming? Etc?)

Thanks. :hide:
 
psneeld said:
Sink a boat?

I thought all the experienced guys here profess shutting seacocks at the dock and sufficient bilge pumping capacity to handle at least one major hose failure....

Certainly have heard many chime in on those safety points.

Everyone should take heed.
Click to expand...

Remember, this particular boat lives in a lift.
 
bayview said:
It looks like the crack originated at the drain penetration. Over tightening or no gasket or just an unfinished hole edge that allowed crack migration. Unless that is a tapered thread plug instead of a straight thread with gasket. That would be poor design.
Click to expand...

No, actually the crack runs just outside the cylindrical indention of the cylindrical drain. The plastic drain plug bottoms out on an o-ring in the indention. My own initial though before close examination was the same as yours, but apparently, as indicated by others here, there are issues with cracks developing in this brand of strainer bowls in various places, and not all were pressure stressed as mine was.
 
Frosty said:
This is probably going to be obvious once I see the answers, but can engine intake strainers be located above the waterline (presuming there is available "above the waterline" space in a given engine room)?

(Obviously the seacock is going to be below the waterline.)

It's been years since I've been on a boat with an inboard and that was sailing days, so we probably paid more attention to the rigging, etc. -- and just accepted the strainers the way they were installed. Plus there's heeling to consider.

Anyway, is it possible to mount engine intake strainers above the waterline on powerboats? And if so, what are the trade-offs? (Priming? Etc?)

Thanks. :hide:
Click to expand...

Yes you can definitely locate the strainer about the waterline. My generator installation was done that way. Don't know if it was by design. Most modern diesel owner/installation manuals will give you a suction spec in inches, that they will self prime to. If I were going to do it, I would have the bottom of the bowl a couple of inches above the water line at most.

Ted
 
Rich, I had something very similar happened to my strainers as well. What I think happened was that I did not seat the metal strainer properly into the bottom slot and I tightened the cap down. That is the only thing that I can think of that would have caused it.
 
kwmeyer13 said:
Rich, I had something very similar happened to my strainers as well. What I think happened was that I did not seat the metal strainer properly into the bottom slot and I tightened the cap down. That is the only thing that I can think of that would have caused it.
Click to expand...

You are more correct than you know. As I was fastening the new bowl onto the upper portion of the strainer I did so with the strainer in place and the cap fully screwed down. I wanted to see if there was interference, and sure enough there was a gap as the six cap screws began to tighten. The stainless steel bale of the strainer basket exerts a lot of pressure on the bottom of the plastic bowl in normal tightening of the cap down to full metal on metal contact. So I cut the bale in two so that the two pieces can overlap acting as leaf springs as the cap is tightened. MUCH better. Anyway, I am back in bidness and five pounds lighter for having to squeeze down there in the tiny space available in BUZILLION percent humidity and surface of the sun heat today. The anchor windlass solenoid replacement will be a snap sitting up there on the bow in the shaded sea breeze....
 
I have had similar interference when reinstalling baskets after cleaning. I'm not sure where the problem originates but when placing the basket it sometimes takes 5-6 tries to get it to drop down fully to allow the cap to be installed without putting too much force on the bail. The difference between fully inserted and not isn't large and if the cap was started and forced down it could be the source of the breakage you experienced.
The fit inside the raised plastic ring at the bowl bottom must be tight and if not seated exactly can raise the basket ~1\4".
 
I know if I cant reseat the basket properly, I need to get the wet vac out and suck everything from the bowl. Then, the basket seats properly after moving it around a bit.
 
In this particular case, a Marine Hardware 0.75 sea strainer which I had removed from the boat in my hand, the basket was clearly aligned properly with the plastic centering tabs in the bowl. The cap will not even start threading into the body with the basket misaligned. In other cases where I have to do the best I can reaching around and into places with restricted access, getting that basket in there properly often takes a couple of tries.

This case was the first time I have ever run across a basket/bale combination actually too long to allow the cap to seat fully without having to force it, and that I feel contributed directly to the catastrophic failure of the bowl.
 
rgano said:
You are more correct than you know. As I was fastening the new bowl onto the upper portion of the strainer I did so with the strainer in place and the cap fully screwed down. I wanted to see if there was interference, and sure enough there was a gap as the six cap screws began to tighten. The stainless steel bale of the strainer basket exerts a lot of pressure on the bottom of the plastic bowl in normal tightening of the cap down to full metal on metal contact. So I cut the bale in two so that the two pieces can overlap acting as leaf springs as the cap is tightened. MUCH better. Anyway, I am back in bidness and five pounds lighter for having to squeeze down there in the tiny space available in BUZILLION percent humidity and surface of the sun heat today. The anchor windlass solenoid replacement will be a snap sitting up there on the bow in the shaded sea breeze....
Click to expand...

Even a blind squirrel finds a nut from time to time.
I had thought of cutting the handle as well but I thought it was designed that way to ensure the strainer stays seated at the bottom of the strainer basket. I do like the idea of the handle being used as a sort of spring in case the strainer does not seat completely.:thumb:
 
The strainer is a knock off of a Groco ARG series strainer. The strainer basket looks like a real Groco basket. It looks like the basket has a hole in the bottom plate that Groco uses to center it on a conical stud in the bottom of the housing. This strainer uses a different method of centering the basket.

It’s possible that the Groco basket is a little bigger than the proper Marine Hardware basket.

I’ve never seen a strainer fail like this. The usual failure mode is small cracks on the flange at the top.
 
HopCar said:
The strainer is a knock off of a Groco ARG series strainer. The strainer basket looks like a real Groco basket. It looks like the basket has a hole in the bottom plate that Groco uses to center it on a conical stud in the bottom of the housing. This strainer uses a different method of centering the basket.

It’s possible that the Groco basket is a little bigger than the proper Marine Hardware basket.

I’ve never seen a strainer fail like this. The usual failure mode is small cracks on the flange at the top.
Click to expand...

Neither have I. This bowl has a circle of four plastic segments in its bottom into which the basket must go. The bottom of the basket is a flat disk with the perforated metal of the cylinder extending a bit below the disk.
 
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