Replacing engine raw water intake thru-hulls

[markrsimon]

Looking for suggestions on what setup to use for replacing my engine raw water intake thru-hulls.

Currently there is a scoop style thru-hull, with a seacock (w/ flange) threaded directly on top. The seacock is sitting off the inside hull by about an inch, and thus is not screwed in place. Removing the 4 tiny screws holding the outside scoop in place, and the entire assembly came loose quite easily.

Q: What’s the preferred configuration, and should I continue to use a scoop pickup?

This seems to be a good setup, and If needed I can add a scoop over the thru-hull. Thoughts?
https://marinehowto.com/seacock-backing-plates/

 

[Korkie]

My first thought is- unless you were having issues, replace it with the configuration that is currently there.

 

[Lazy Daze]

Somebody, somewhere along the line messed with that thru-hull. The triangular flange should be securely mounted to the hull bottom - typically with a glassed-in piece of wood so you're not screwing directly into the hull. Looking at that picture, it appears at one time it WAS secured. Currently, you're relying only on the actual thru-hull's nut. Every time that seacock is opened/closed it's torquing that nut. It's not a "the sky is falling" thing, but it would be worrisome to me... and 'could' result in a 'the boat is sinking' thing.

 

[markrsimon]

well, thats it - there is no thru hull nut.. just the thru hull and the seacock. so aside from those four little screws on the scoop and some sealant - I have an issue that needs fixed.

Looking to understand either what the original setup should be, or what to put in place. Mainly, do I need a scoop intake or not?

 

[Lazy Daze]

Holly mackerel... that's all that was holding that together?!?! Play the lottery tonight!

A scoop with strainer (slots) would help to keep bigger stuff out of your filter (onboard strainer).

 

[b_arrington]

My original through hull has the integrated scoop on the outside, like this.


It worked fine but I replaced it because the scoop was not removable for maintenance and cleaning out barnacles. It got clogged up and I had to break a couple slots to clean it out.

I replaced it with a straight through hull and a Grocco strainer with an access door. Much easier to maintain and I can get some anti fouling in there.


IIRC, I didn’t have to remove the factory seacock. I was able to unscrew the old scoop and screw in the new through hull. Using the lugs inside the fittings.

 

[markrsimon]

Thanks for the info. Was trying to avoid the fixed scoop given zebra mussels and the like, but also worried about potential overheating with a regular thru hull. Gonna give the regular thru hull a try, and if I run into water intake issues, Ill add the strainer afterwards. Going to glass in a backer for the flange as well, to get everything structurally sound.

 

[b_arrington]

Thanks for the info. Was trying to avoid the fixed scoop given zebra mussels and the like, but also worried about potential overheating with a regular thru hull. Gonna give the regular thru hull a try, and if I run into water intake issues, Ill add the strainer afterwards. Going to glass in a backer for the flange as well, to get everything structurally sound.

I would be concerned about cavitation and resulting overheat with a plain through hull. A scoop will force water into the supply hoses, where you make get air pockets from the lip of the plain thru hull. There’s likely a reason that scoops are standard equipment.

You might want to consider adding the strainer now to avoid having the pull the boat out later.

 

[Lazy Daze]

I'd be hesitant to go without a scoop, as well. Get the trap door like Brad mentioned and it will make it easier to get rid of those little buggers - or, as he mentioned - paint the inside.