Clam Shell Orientation

[Steve A.]

I hate to ask a stupid question except it has been a topic of intense discussion between power boat and sailboat owners at lunch. What is the correct orientation of a through hull clamshell for raw water intake? The power boaters say the slots should be facing forward and the sailboaters say the slots should be facing aft. Can I get some feedback from sailors? (the picture attachment didn't seem to work, sorry).

 

[CaptDanS]

ABYC says

The reason the orientation is different is because when a powerboat is underway the engine is always running but in a sailboat under sail you do not want water to be forced into the raw water intake. Generator intakes should also face aft for the same reason. In some engines on sailboats or generators on powerboats, facing the strainer forward has caused water ingestion into the engine when the engine was not running but the boat was underway. Dan Sheehan

 

[Ed Schenck]

That's affirmative.

When Dan responds you can take it to the bank. And if you are the sailor in the group then you will take in a lot less filter clogging "stuff" with the clamshell facing aft.

 

[Don12364]

Dubious Reasons

Yachtsmen want to have their clamshells facing aft so the intake doesn't block and overheat the engine.It is for this very reason that yachtsmen want power boaters to have theirs facing forward ;D

 

[Paul Akers]

Let Me Know!

This is an age-old conflict. I have alays oriented it aft for the exact easons that have been specified. I ran into the same problem when I wanted to install one on my boat. Hunter's don't have them, but I nreeded one when I took my boat to Maine one summer. There was so much weed up there, I clogged 5 times. I oriented it facing AFT and have not had any problems!

 

[Steve A.]

Thanks for the input!

I keep my 1992 H28 in Boothbay Maine during the summer and sail down to Newburyport, MA to lay up for the winter. I recently installed a integrated thru hull clamshell with the slots oriented aft. Thanks for your responses and confirming that I installed it correctly. I launch on 1 May and sail North to Maine the same day. During the several years that I have been sailing in Maine without a clamshell, I have clogged several times (hopefully those days are over now).

 

[Dan Johnson]

For those of you...

that have had a clogging problem, carry a 12 volt tire inflator and a hose the same size as the inlet hose barb with a tire valve clamped into the opposite end of a short piece. Close the thru hull, pull off the hose, clamp on the valved hose, pump it to about 40 PSI, and "Fire One" (quickly open the thru hull valve) or two or three, however many it takes to blow the clogging material out.

 

[Fred Ficarra7897]

All Hunter had to do was to provide a screen over the inlet.

Wonder why they didn't (or don't). When our boat was new we had several weed-clogs. The Perko strainer did NOTHING to stop them. During the first haul-out I installed one of those colander style baskets over the inlet. Not one more clog. Works on the watermaker inlet too.

 

[Steve A.]

Perko?

What did the Perko strainer look like? The one I installed is a bronze thru hull that has an integrated clamshell with the forward end being solid rounded and the aft end being slotted. There is lots of weed up in Maine (Sheepscott River) so I finally decided to try a strainer. However, it doesn't look like a colander.

 

[Paul Akers]

What I Did!

When I clogged up in Maine, here is what I did to relieve the problem. I would shut off the raw water intake valve (after shutting down the engine, of course). Remove the intake hose from the thru-hull. Then I would take my Avon foot-inflator and place it over the intake nipple. And press the inflator just as I opened the valve. The back-pressure was enough to clear the clog. I'd reassemble, restart and be on my way. It is said that an airhorn will, also, provife the necessary pressure. I know a person from Maine who regularly uses one and, it too, performs wonderfully.I'm relocating my boat up to Maine in June. If the problem recurrs after installing the integrated thru-hull w/clamshell, I'll let you know.Steve, check us out. See the related link.