Engine inlet thru-hull

[PaulJacobs]

For the third time in the past four years our engine is overheating.  I will check the water pump impeller, but I suspect it is fine.  The past two events were the result of sea grass clogging the sea water engine inlet.  On Pleiades there are three through hulls almost in an athwartships line: (1) The engine inlet, (2) the head sink outlet, and (3) the head inlet. All three thru hull inlets are relatively small (1/2" diameter ???) and are even somewhat smaller due to the build-up of bottom paint on the insides of the thru hull. Thus, they can readily become clogged with sea grass.  I removed the in-line water filter and found a wad of sea grass, which I cleared out, but the engine still overheated afterward.

Pleiades is still in the water.  I am thinking that I might: (a) close the raw water inlet sea cock, (b) remove the hose from  the (upper) water filter end, (c) hold the upper end of the hose ABOVE the water line, (d) open the sea cock, (e) push a thin rod down the inside of the hose to push accumulated sea grass out, (f) check that the opening is clear by gradually lowering the upper end of the hose until it is just below the waterline and assuring that water indeed streams in, (g) once clear, re-connect the upper end of the hose to the water filter.

Has anyone else ever done this?  Did it work?  The previous two times a dear friend - who is much younger than I - kindly held his breath, swam under the hull, and poked a screwdriver into the raw water thru-hull and voila, a wad of sea grass came out, and the engine ran fine.  Unfortunately, he is no longer available, and at 83 I cannot swim under the hull and hold my breath long enough to clear any blockage.

Finally, about 4 years ago I read an article that indicated that when microscopic organisms in saltwater die, they emit nasty odors.  Previously, we used saltwater to flush Pleiades head.  Since then, we use fresh water, and the head has worked perfectly and smells better.  The sea cock for the head inlet has been closed for four years!  I am thinking that over the winter I will re-plumb this hose to a "Y" diverter valve in the head locker. When - not if - the raw water engine inlet eventually gets clogged again, I would then be able to simply switch the diverter valve to provide raw water for the engine.  I could then disconnect one hose and repeat the process noted above to clear the clog.  Any thoughts or suggestions?

Dr. Paul F. Jacobs
Pleiades
1990 C-34 MK1.5 #1068
Wickford, RI

[Patches]

Paul:

Very easy, I do this a few times a year.  I keep a piece of wooden dowel about 16 inches long in the cabinet above the head.  I typically:

1.  Close the engine inlet thru-hull

2.  Remove the hose from the thru-hull

3.  have the dowel at the ready

4.  open the engine thru-hull  (water ingress is minimal, and goes straight to the bilge)

5.  push the dowel down through the thru-hull to clear the obstruction.

6.  close the thru-hull and reconnect hose.

I have changed out my strainer to a Vetus which I find much better to access and view.  I mounted mine just below the secondary Racor fuel filter, but I have the original "R24" type filter so it fits.  I am changing out to the Racor 500fg over the winter, which will require me to move the Vetus strainer over to the fiberglass wall inside and to the right of the sink cabinet door opening.  I already installed an RV-type plastic fuel door just below the shower sump pump switch to make accessing the strainer easier once I complete the installation.

Patches

[PaulJacobs]

Hi Patches,

Thank you for your very excellent response.  Three questions:

1.  What diameter dowel do you use?

2.  During the brief interval AFTER you have cleared the blockage how high is the resulting "water fountain"?

3.  It surely takes some amount of time to re-close the inlet thru-hull while the water is coming in.  Very roughly, how much sea water do you think comes in?  Hopefully only a few gallons - which the bilge pump can easily handle.

Thanks again for your wonderful response.

Dr. Paul F. Jacobs
Pleiades
1990 MK 1.5 #1068
Wickford, RI.

[KWKloeber]

Paul

Clearing blockages as you describe is common.  Yes a hose above the waterline works but makes it more difficult. For that reason I've had some customers replace w/ 3/4 hose so pushing a down thru it is easier.
But if your dowel is close to the ID of the thru hull barb there's little leakage past it for the short duration you're pushing out the wad.  It's a non issue because you're going to close the valve right after the dowel passes up through the ball.
I don't know the ID of the thru hull barb and/or the ball valve hole so you might experiment to get the appropriate dowel diameter.
If you have access to compressed air at the dock that's another way that I've used.

[Stu Jackson]

In 25 years I have only had ONE indication of that thru hull being blocked.  I removed the inlet to the raw water pump and used my dinghy foot pump to back-pressure the hose.  It cleared immediately.  There's more than one way to deal with this issue.

[mark_53]

There's more than one way to deal with this issue.

Yes, I used a 3' piece of 3 wire 14 gauge Romex. Open the thru hull, if water comes gushing out, it's not blocked. Close quickly.

[ErikN]

For what it's worth, I recently did this for the first time while out cruising. I didn't have a tool that was just the right size to prevent a gusher--it spurted two or three inches above the thru hull after I cleared the blockage, but the whole process probably let less than one gallon into the bilge. If I weren't so clumsy it would have been considerably less.

I tried using the dinghy pump first, but it didn't help. Maybe there were some barnacles growing in there? Needless to say, I will be cleaning that thru hull more frequently in the future.

Erik

[Ron Hill]

Paul : I had the same problem twice and poked it out with a 3/8" wooden dowel both times.  Then I lightly caulked a bronze round strainer to the outside of the hull over the thru hull inlet.  25+ years later I have NEVER had a clog again.

I caulked a dab in 4 places - I did that so if I found out that the strainer was a problem then I could poke it off with that dowel!!

A fthought

[PaulJacobs]

Nothing is ever as simple as one might hope!  I got to Pleiades yesterday intending to use a dowel to clear the raw water inlet thru-hull blockage only to find that the present installation includes a 90 degree nylon elbow coming directly out of the thru-hull.  This precludes using a dowel to clear the blockage.  This winter, when on the hard I will look into removing the 90 degree elbow and connecting the hose from that thru-hull to the raw water strainer.

In the meantime I came up with an alternative plan.  I will remove the upper end of the head sink drain and connect it to the strainer.  This fitting is a straight one, so I could use a 3/8" diameter dowel to clear blockage - WHEN, not if - it eventually gets clogged.  We hardly ever use the head sink, and I believe its thru-hull is identical to the one currently being used for the engine raw water inlet, so this should work well.

Paul

Pleiades
C-34, MK 1.5 # 1068
Wickford, RI

[KWKloeber]

Paul

So you're saying the 90 is hard piped to the strainer, not a 90 hose barb?
Careful bout old fittings - Catalina was notorious for using pvc and nylon not approved or appropriate for below waterline use!

You could try Stu's foot pump method?

[ErikN]

One of our dock neighbors swore by a modification he had made. He added a Y between the thru hull and the raw water strainer, and he attached a short piece of hose with a plug fitting on the end. He could then unscrew the plug and insert his dinghy pump hose to blow out the thru hull without undoing any clamps. It seems like a fairly regular blow-out might help prevent some of the harder clogs that require a rod. Are there any potential problems with this setup?

[KWKloeber]

Are there any potential problems with this setup?

Not particularly except if the pump doesn't do the trick.  It would be dual purpose if it were set up to periodically flus but be able to dowel the thru hole if needed.

In Paul's case (if I picture it correctly) IIWMB I'd have a tee w/ a plug atop the valve; then it could be cleared thru the tee w/o disturbing any plumbing/clamps/hoses.
(naturally using all approved materials.)

[waughoo]

The T sounds like the best Idea I have seen yet for this semi regular problem.  Makes for a quick solution to clearing a plugged thruhull fitting.

[PaulJacobs]

DONE!  I switched the sink drain thru-hull with the engine raw water inlet thru-hull, by simply taking the hose from the bottom of the head sink and moving it to the connection at the raw water strainer, and conversely replacing the hose from the 90 degree nylon coupling on the engine raw water inlet, (the old hose was not quite long enough), up to the bottom of the head sink.

With all thru-hulls shut not a drop of water entered the boat!  By far the hardest part was removing hoses from barbed connectors.  Once everything was re-connected I double 316 SS hose clamped all connections, opened all thru-hull valves, crossed my fingers, started the engine, and it ran beautifully.  Nancy and I then went on a little overnight "mini-cruise" from Wickford to the bight near Potter's Cove on Prudence Island.  Yesterday, on returning to Wickford the winds were extremely light (< 3 knots) until almost 5 pm, so we wound up powering for over two hours.  The engine ran beautifully with no tendency to overheat, and I could see abundant cooling water exiting the exhaust - after kneeling down on the transom, holding onto a pushpit stanchion and bending far over!  That is one of the very few things I do NOT love about the C-34; it is NOT easy to see exhaust water exiting from the hull.

Finally, with a straight entry on the former head sink drain thru-hull - now the engine raw water inlet thru-hull - I can now use a dowel to clear any future blockages! .

Paul Jacobs
Pleiades
1990 C34 #1068

[KWKloeber]

Paul



Schmear a bit of SuperLube gel or tef-gel or lanokote inside the hoses and on the barbs - they will be easy to remove when needed!

Once again if you missed it, nylon and pvc fittings are NOT approved for below waterline hoses and should NOT be used. YBYC!