raw water blockage

[HalcyonS]

hi everyone,
I haven't been here for a while - all sorts of life complications.
So Today, I started the engine - having accidentally left the raw water intake open for a week - ran nicely with cooling water, then no cooling water. Took the water pump cover off - good impeller.
I've got a big bronze thru hull and valve, and as I recall - it been a while - a perforated plate over the intake. Nav le goes via about 4' of 1" hose to a big bronze strainer - ~ 10" x 4" original Wilcox Crittenden. So I'm guessing the blockage is in the thru-hull or in the line between valve and strainer.
How should I test? Thinking aloud here - I guess I'll disconnect the strainer to valve hose at the valve and drain back from strainer into bilge, and I can open valve to see flow from outside. If the blockage in in the thru-hull, I guess I need to dive, right?
That should isolate blockage location - unless the blockage is in the block, or the v-drive. Does this happen? How would I diagnose/cure?
Any suggestions much appreciated.

[JOHN COOKSON]

You could try disconnecting a cooling system hose somewhere at the midpoint of the water flow inlet -> to final outlet them start at that point and work back to the inlet or forward to the outlet until you find the blockage. The alternative is to start at one end of the cooling system and work from that end to the other end until you find the problem.
Manifolds have a nasty habit of becoming blocked.
This would be a good time to plumb for the Thatch Modification if you don't have it already.
You're RWC I presume?

ex TRUE GRIT

[Peter]

I was warming up my engine one day when the exhaust stopped spitting water. Took the cap off my winterizing tee and no water with thruhull open so must be plugged thruhull. Removed hose from winterizing tee and tried to blow it clear. No luck.

Thought about going to get an air compressor to blow it out but then it occurred to me to try connecting the bilge pump outlet to the hose and pumping water back through it. Had to dump a few pails of water in the bilge but it did the trick. A large jelly fish came up once it cleared

No diving required

Hope that helps

Peter

[Dave Neptune]

I was motoring across the Catalina Channel one winters day with my dog. About half way across the engine temp began to spike, no water! I spent the next hour or so trying to get the offending obstruction out of the intake without diving. When I finally decided I needed to dive I sat down below looking at the engine and took a shot in preparation for the dive. Well I got another idea and with some duct-tape and a fire extinguisher I managed to blow it out. However the extinguisher popped loose on the second "ga-dush" and blew water and powder all over the cabin. Popped the hose back on and was underway. I had a bit of a mess but was running cool. As I was cleaning up I noticed an outline of me that was clean against the starboard bunk and overhead.

Dave Neptune

[edwardc]

Another old trick: If you have an open thru-hull (not one with a slotted cover), you can ream it open from the inside with a small piece of rebar.

[Al Schober]

I've never been a fan of external strainers on the water inlet. I've had blockages in the past, and been able to clear them by removing the inlet hose and pushing a piece of dowel down through the ball valve and the hull fitting. Close the ball valve while you reconnect the hose, then you're good to go.

[HalcyonS]

Originally Posted by edwardc

Another old trick: If you have an open thru-hull (not one with a slotted cover), you can ream it open from the inside with a small piece of rebar.

yeah but - boat is in the water ....

[Ando]

Originally Posted by Peter

Thought about going to get an air compressor to blow it out but then it occurred to me to try connecting the bilge pump outlet to the hose and pumping water back through it. Had to dump a few pails of water in the bilge but it did the trick. A large jelly fish came up once it cleared

No diving required

Hope that helps

Peter

What’s the size of your pump?

[Peter]

Pump is a Rule LP900S LoPro 900 GPH

Which seems like a pretty small gph if a “ A one-inch hole 12 inches below the waterline will flood the boat at a rate of 19 gallons per minute”

However it did the trick for clearing the thru hull

Had to flood the bilge about three times to fully clear the jellyfish though.

Peter

[Administrator]

Originally Posted by Peter

Pump is a Rule LP900S LoPro 900 GPH

Which seems like a pretty small gph if a “ A one-inch hole 12 inches below the waterline will flood the boat at a rate of 19 gallons per minute”

However it did the trick for clearing the thru hull

Had to flood the bilge about three times to fully clear the jellyfish though.

Peter

I think the success here may have had more to do with pressure than volume.

Bill