Replacing a thru-hull with a scoop strainer

[scboy]

I have searched the web, and asked a few folks, but I have not found any good info on substituting a scoop strainer for a mushroomhead thru-hull. I know that Maine Sail has done some good articles on replacing seacocks, thru-hulls, alternate backing plates, etc...., but it seems that no one has done much with scoops.

The main purpose for my scoop is to provide positive pressure for the baitwell pump while running. I had also hoped that it might provide enough water through the baitwell pump to avoid having to run it while under way.

The picture below shows what is installed in the boat right now. I bought the boat this way and know that it is installed without a proper seacock. I do not want to install a seacock, but want to add a strainer scoop in lieu of the thru-hull with a reinforced flange on top of a backer plate. I perfer keeping the ball vavle that I have now for easy change out if it is needed at a later date.

(I tried posing a pic but my post count has to be two or greater.)

The biggest problem that I am trying to work out in my head, is how to install the reinforced flange after the scoop is attached to the hull. The scoop really does not allow for screwing it into the flange after the flange is mounted, since the scoop has to be facing towards the bow in the end. I'm afraid that if I try to screw it in the whole assembly will get tight when the scoop is not facing the bow.

OK everyone fire away. I hope I have explained the problem well enough.

[scboy]

Building up my posts so I can post a picture

[scboy]

Picture for the above post.

[danielgoldberg]

I don't have an answer to your specific question (sorry), but this setup looks pretty scary. You don't have a valve on the through hull, so if that elbow fails for whatever reason (maybe someone stepping or dropping something on it) you have no way to close the hole. I'm not really sure why you don't want a true seacock, but the valve should go directly on the throughhull, and the elbow come after the valve, FWIW.

[scboy]

I agree the setup is scary, that is why I started researching how to fix it. A flange adapter plate is like the sea **** without the valve. You add the ball valve to the top of it. It allows for change out of the ball valve if you need to without changing distrubing the thru-hull.

Maine Sail gave me the idea. See the below links.

Replacing Thru-Hulls and Seacocks Photo Gallery by Compass Marine at pbase.com

Seacock & Thru-Hull Primer/Pre Information Photo Gallery by Compass Marine at pbase.com

[danielgoldberg]

I'm familiar with that product (and I actually have one on my boat). IMHO, they too are a compromise, albeit a lot better than just screwing a ball valve onto a through hull.

But that said, now I think I understand a little better what you're thinking of doing. If you are determined to go that way, be sure to put the flange adaptor to the through hull, the ball valve to the flange adaptor, and then screw an elbow into the ball valve. In this application, however, I think you would be better off with a traditional seacock, and then just screw the elbow directly into the seacock. Less complicated, more robust, and it will not protrude as high. And if you use a true Marelon seacock and elbow, it will cost a lot less too, not to mention avoiding any concern about corrosion. Just one dope's opinion.

[Maine Sail]

Originally Posted by danielgoldberg

I'm familiar with that product (and I actually have one on my boat). IMHO, they too are a compromise, albeit a lot better than just screwing a ball valve onto a through hull.

What do you consider a compromise about the flanged adapter? I have measured the wall thickness of many seacocks and the flanged adapter is as thick or thicker than most. I am helping a friend replace some Apollo seacocks that are about ten years old. They have zero corrosion yet the ball seats are done and opening and closing them is a bear even after trying to clean and lube them. Had a flanged adapter been used this replacement would have taken ten minues not ten hours and involved patching barrier coat etc. ect..

Originally Posted by danielgoldberg

If you are determined to go that way, be sure to put the flange adaptor to the through hull, the ball valve to the flange adaptor, and then screw an elbow into the ball valve. In this application, however, I think you would be better off with a traditional seacock, and then just screw the elbow directly into the seacock. Less complicated, more robust, and it will not protrude as high.

In this application I agree 100% with coming off the flange with the valve then elbow, but in many applications you simply do not have the height to do so and there are thousands of boats out there with elbows off the thru-hull. While certainly less than ideal it can work in a protected area of the vessel and there are many boats where you have no choice unless you want to re-locate a thru-hull. The OP clearly has the height and the ability to put the elbow after the seacock. This also looks like an open area that is not well protected and the lever arm of that set up becomes more dangerous when in an un-protected spot..

Originally Posted by danielgoldberg

And if you use a true Marelon seacock and elbow, it will cost a lot less too, not to mention avoiding any concern about corrosion. Just one dope's opinion.

I'll give you the corrosion piece but the price of Marelon is not less, at least where I shop..

3/4" Flanged adapter = $24.99
3/4" Groco valve = $18.80
TOTAL Flange/Valve = $43.79

3/4" Marelon Seacock = $44.91

3/4" Groco Flanged Seacock = $32.39

P.S. Marelon flanged seacocks are basically flanged adapters too. The flange is threaded into the bottom of the valve then kept from un-threading with a very small stainless pin..

[scboy]

This boat is an Mako 191. It does not sit in the water. I do plan on taking this boat to the nearshore reefs and live bottom off the SC coast. The longest run will be 25 mi out. The hull will be pounded. Probably for no more water contact than it will see. I should just put an seacock on and be done with it. I still have the problem of getting the scoop strainer to the seacock though.

Picture of the scoop:

Groco Bronze Thru-Hull Scoop Strainers

[Maine Sail]

Originally Posted by scboy

This boat is an Mako 191. It does not sit in the water. I do plan on taking this boat to the nearshore reefs and live bottom off the SC coast. The longest run will be 25 mi out. The hull will be pounded. Probably for no more water contact than it will see. I should just put an seacock on and be done with it. I still have the problem of getting the scoop strainer to the seacock though.

Picture of the scoop:

Groco Bronze Thru-Hull Scoop Strainers

A scoop is no different than a thru-hull and either can be threaded into a flanged seacock or a flanged adapter and with either you'll still need to cut them to insert length. On a sail boat you'd want the strainer facing aft but on CC, for what you'd want to do, you'll want it facing forward. If you can thread it in tight enough, and get it to align properly you can sometimes avoid the hull screws.

Be sure this scoop won't be out of the water on plane and that it is close enough aft to not leave the water when planing..

[danielgoldberg]

Hey there MS. You certainly are more knowledgeable about this stuff than am I, but since you asked ...

It's a compromise not because the specific piece of hardware isn't first rate, which it is. But you still are threading a ball valve into the flange adaptor, and that presents another potential failure point. It's easier to snap off the ball valve, there's more of a chance the connection will leak, etc. You are right that if you need to replace the valve it's easier to change just a ball valve, but a properly installed, properly maintained, quality seacock is not going to fail with anything close to regularity, if ever. Moreover, you don't absolutely need to through bolt the seacock through the hull. You could laminate in either a resin soaked piece of ply, maybe G10 or something comparable, and bolt to that alone.

As to your second point about not having enough room to put the ball valve onto the flange adapter and the elbow after that, isn't that an argument for using a true seacock? If you have enough room for the flange adapter, you most likely have enough room for a seacock, no?

In terms of pricing, at least at West and Defender, the Marelon units uniformly are less expensive than the bronze seacocks. And at the larger sizes (an inch or more), the bronze are substantially more expensive. Seems you found a serious sale at Hamilton re: the bronze seacock. I wasn't comparing to the flange adapter with ball valve, but your numbers bring them within pennies anyway.

I didn't know that about the Marelons re: the pin! Learn something new every day I guess.

Hope you and your family had a good holiday!