Can't find the intake water strainer

May 19, 2021
5
Hunter 33.5 Burlington Bay
Hello all - I have a 1988 Hunter 33.5 which has begun overheating. I'm pretty sure it's the fresh water intake clogged somewhere, since we are in pretty contaminated water. Prior to getting in said contaminated water to clear out the intake screen on the bottom of the boat, I'd like to try blowing it out from inside the boat. Only problem is... I can't find the darn water strainer! Can anyone clue me in on where it is in this boat?

Thank you!
 
Feb 26, 2004
21,950
Catalina 34 224 Maple Bay, BC, Canada
I'd like to try blowing it out from inside the boat. Only problem is... I can't find the darn water strainer!
You don't need to. Take the intake off the inlet to the rw pump on the engine.
Some boats actually came without intake strainers - believe it or not, but it's true. That did eventually end though.
to clear out the intake screen on the bottom of the boat
You should seriously reconsider this thing.
Why External Strainers are a Bad Idea 101 (Maine Sail) Why I Dislike Like External Strainers
 
May 19, 2021
5
Hunter 33.5 Burlington Bay
Ok, I found the filter strainer, and the seacock where it comes through the hull. It's under the rear berth floorboards on the port side of the boat. The hose between the seacock and the strainer has an outlet, looks like where a previous owner put a spot to blow the external strainer out without disconnecting anything. I opened that outlet, and water is flowing freely, so that's not it. Then I closed the seacock - visually I can see the water in the strainer (clear sides) and then I started the engine. I expected the engine to suck the remaining water out of the strainer body, but absolutely nothing happened. I then disconnected the intake hose from the engine side, and there was a random piece of rubber stick in the intake side of the pump body. Not *blocking* the intake per se, just kind of partially blocking it. I removed that piece of rubber, and blew out the intake hose from the engine side. Nothing came out of that but water. I reconnected the hose and tried again, but still no suction from the engine. I believe I may have a damaged / non-working pump / busted impeller. Thoughts?
 
May 17, 2004
3,469
Beneteau Oceanis 37 LE Havre de Grace
Strange that there would be a piece of rubber on the intake side of the pump - usually the impeller breaks down and rubber bits go downstream from there. I’d definitely open the impeller cover and have a look. Impellers don’t last forever anyway so unless it’s been changed recently it’s probably due. Once you have a look at whether the impeller is intact you can figure out if you need to look further downstream, like at the heat exchanger or exhaust elbow.
 
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Feb 26, 2004
21,950
Catalina 34 224 Maple Bay, BC, Canada
I reconnected the hose and tried again, but still no suction from the engine.
The engine doesn't suck the water, the pump does.
You MUST prime that pump with water before it will work. Why? Because pumps are made to move water and will NOT move air. To do that, open the seacock and suck on the hose until water comes in, then connect it to the pump.
Good luck, it's a pretty easy thing to do. Of course, check the impeller first.
 
Apr 5, 2009
1,616
Catalina '88 C30 tr/bs Oak Harbor, WA
While it is true that a Centrifugal pumps pump will not self prime, the same is not true for a positive displacement pump such as a vane, gear, diaphragm or screw pump. the raw water pump is a rubber bladed vane impeller pump so it will self prime up to about 2/3 atmosphere (20')

.
 
May 17, 2004
3,469
Beneteau Oceanis 37 LE Havre de Grace
While it is true that a Centrifugal pumps pump will not self prime, the same is not true for a positive displacement pump such as a vane, gear, diaphragm or screw pump. the raw water pump is a rubber bladed vane impeller pump so it will self prime up to about 2/3 atmosphere (20')

.
That matches my experience too. I’ve never had to prime my raw water pump. Once out of many years I’ve had to pour a little water in the strainer bucket, but otherwise it’s always self-primed.
 
Apr 5, 2009
1,616
Catalina '88 C30 tr/bs Oak Harbor, WA
That matches my experience too. I’ve never had to prime my raw water pump. Once out of many years I’ve had to pour a little water in the strainer bucket, but otherwise it’s always self-primed.
If your raw water pump does not pull water through the strainer, you might think about changing the seal in the strainer because that would be a sign of an air leak someplace.
 
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Ward H

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Nov 7, 2011
3,123
Catalina 30 Mk II Barnegat, NJ
My raw water pump would stop pumping water after a day sail.. Turned out a bad o ring seal for the pump cover was the culprit.
So, yes they do not need a prime but an air leak will prevent them from doing so.
Good point from @Hayden Watson about checking the strainer seal.
 
May 19, 2021
5
Hunter 33.5 Burlington Bay
It was the impeller - what I thought was the pump was the exchanger, which explains the rubber on the supply side - that's after the pump :). I've attached some pics of the pump taken off, then apart. The impeller seemed like it hasn't been changed in a long while - it was amazingly hard to pull - I ended up modifying a small gear puller to get it out. Thanks for all your advice on this! Pics are: a piece of impeller I found in the hose, front of the engine, location of the strainer filter and seacock, the pump itself, back of pump, impeller cover, ruined impeller exposed. I'll be picking up a replacement plus gasket tomorrow and re-installing. Should I prime this? or does this type of pump not need it? Edit: Just read the short thread here on priming - I've got less than 6' of hose, so I'll try it unprimed, then prime it if that doesn't work.
 

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May 17, 2004
3,469
Beneteau Oceanis 37 LE Havre de Grace
I usually put just a little soapy water in the pump housing after installing the impeller, just to give it a little lubrication until the water gets to it. Doesn’t need to be full or anything, just a little coating around the dry rubber. Don’t forget to open the seacock again before you start the engine. If you don’t see water out the exhaust after maybe 15 seconds I would stop and reinvestigate.
 
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Apr 5, 2009
1,616
Catalina '88 C30 tr/bs Oak Harbor, WA
Wow, that is one sad impeller. I have seen them with 1 or 2 broken vanes but never all of them. As Davidasailor26 said, a bit of dish soap and it should self prime. If it does not you still have a problem somewhere.
 
Oct 2, 2008
3,584
Pearson/ 530 Strafford, NH
I use a zip tie on new impellers to squeeze the rubber vanes in one direction. Then I use the glycerin to lube the shaft and all the vanes before assembly. The zip tie slides off as I guide the impeller on to the shaft, that makes the exchange so much easier.
 
Jan 7, 2011
2,908
Oday 322 East Chicago, IN
There must be a lot of rubber bits in your cooling system looking at that old impeller… make sure you check the hose and HX if you don’t know where all of the pieces are, or if you aren’t getting good flow out the exhaust.

Is that a 2GM20F or similar? The backwards water pump is the same as my 2GM20F. A pain to have to pull the pump to get to the impeller, but necessary.

Greg