Trick for Plugged Raw Water Through-Hull

[Sailing Steve]

Last week I was leaving the harbour when I noticed that the engine water temp was quickly climbing past 190F, and water was no longer coming out of the exhaust, so I killed the engine and coasted.  A quick cleaning of the raw water strainer failed to resolve the problem.  Leaving the strainer cap off, I re-opened the seacock, and no water flowed telling me there was a complete blockage in the through-hull.  I ultimately dropped anchour, removed the hose between the seacock and the strainer allowing me to repeatedly shove a large flat-bladed screwdriver through the open seacock/through-hull, clearing the blockage; Blowing into it was totally ineffective (I believe you can only produce about 2 - 4 PSI with your lungs, despite the red face, broken blood vessels in the eyes etc. suggesting otherwise).

In wishing to prove out the rest of the cooling system (impeller, HX etc.) flow before getting back underway, I discovered that placing the head sink/shower head into the water strainer via the removed cap, and turning on the sink/shower head tap partially, easily supplied enough water to keep the strainer full, very effectively cooling the engine.  Not only did this prove out that there were no other cooling system issues, but I realized that a person could keep the engine running to motor to a safe location, if required.  Of course, this would only work as long as there was water in the tanks 

[Ken Juul]

Steve,
Great idea about using the sink hose. 

Couple of thoughts.  Using your dingy pump to blow the plug clear is probably a better idea than your lungs.  Plus if it does clear you won't get a face full of water when you stop to take a breath 

Check your impeller.  It does not take long with no water flowing to damage the blades.  Even though all looked normal on your return trip, if they are cracked they will fail in the near future.  Trust me, Mr Murphy will ensure it will happen at the worst possible time.

There is a project that adds a "t" to the intake.  The strainer is feed from the foot of the T.  One end of the cross is capped, the other is attached to the thru hull.  If you do get a plug you can unscrew the capped side and clean the plug out with a peice of dowel (3/8" I think) that is handily stored next to the thru hull.

[Stu Jackson]

Good thinking.  Also try reply #2 here:  http://c34.org/bbs/index.php/topic,4458.0.html

[Sailing Steve]

Good points Ken and Stu - Thanks.

[Roland Gendreau]

I experienced the exact same issue recently...and I cleared the blocked thru hull by placing the outlet of an air horn against the open strainer body (it fit almost perfectly) and the air pressure cleared the debris with 1 quick blast. After which,  raw water flowed nicely out of the strainer.

Roland Gendreau
Gratitude #1183

[Stu Jackson]

I think the real TRICK to this is to avoid always suspecting that EITHER the HX or the impeller on the rw pump are the culprits.  Step-by-step examination has many, many times, led to the clogged thru hull, 'cuz that's where the H2O comes from, but since it's outta sight, it's...

[Ron Hill]

Guys : Look at reply #3 that I posted in the site Stu references.  Ms. DeWinchel came up with the dingy pump idea (to blow out a stoppage) that I posted in the Mainsheet Tech notes back in 1997/98? !!!

As I mentioned there is NO Substitute for a strainer on the outside of the raw water engine thru hull.  Great info in those 15 to 20 year old owner fixes to problems that still plague owners today!!!
A few thought.   

[lucky]

I've had my engine water flow stop up and I took the hose off engine sea cock and put it on the sea cock for the head,worked fine until I got the proper repair.
Al Landry
Lucky #13
c34

[chuck53]

The thru hull for my A/C water pump got clogged a few weeks ago with a stinging nettle and after a failed attempt to back flush with a water hose, a buddy suggested the air horn method to me.  I never would have thought of it, but it worked.  An air horn has a lot of pressure to put on a blockage.

I experienced the exact same issue recently...and I cleared the blocked thru hull by placing the outlet of an air horn against the open strainer body (it fit almost perfectly) and the air pressure cleared the debris with 1 quick blast. After which,  raw water flowed nicely out of the strainer.

Roland Gendreau
Gratitude #1183

[Stephen Butler]

We used to use an air horn to blow out the holding tank vent every year.  We store the boat on the hard in Florida and despite taping over the vent, we always seemed to loose the tape to weather and then end up with a few mud-wasps in the vent.   We have since place a ss hose clamped over the vent when storing, but an air horn is a great blockage clearer.