Screwing into solid fiberglass

[OS2Dude]

Second (Third?) the idea of no external strainer. But do be sure to check the thru-hull! We have a raw water cooled A/C system. We leave it on (it has a dehumidifier function) over the winter and when I went up for a few days to get things ready for spring it started erroring. Eventually I got around to checking the intake, and it was almost solid with pine straw. The internal strainer was full of leaf and pine straw debris, and when I removed the hose and opened the thru hull an almost solid mass of pine straw oozed out like an old playdoh machine. Once clear the A/C was fine again.

[Ken Pole]

I think an internally-mounted raw water strainer (Vetus, e.g.) looped between the through-hull and the block would be best. When weeds get sucked in, it's a simple matter to unscrew the lid and empty the strainer basket.

[HopCar]

Don’t over think this. You’ve got a thick hull and there will be little load on the screws. I’d bed it in 5200 and use short self tapping screws.

Yes you will be able to remove it. 5200 is not the same as welding. When you want to remove it just warm it with a propane torch. It will just pop off.

A lot of people on this forum are suggesting not using an external strainer. Another option would be to use a good external strainer and eliminate the internal strainer. I’m seeing a lot of big powerboats go this route.

I installed a Groco APHS external strainer on my boat and never had to clean the internal strainer. If you get growth in the thru-hull, it opens to give you access.
https://www.groco.net/products/raw-w...er/aphs-series

[Q Xopa]

Originally Posted by Ken Pole

I think an internally-mounted raw water strainer (Vetus, e.g.) looped between the through-hull and the block would be best. When weeds get sucked in, it's a simple matter to unscrew the lid and empty the strainer basket.

If youre going to have external strainers I like these https://www.groco.net/products/raw-w...er/aphs-series

[Squanderbucks]

The external strainer (also known as perforated scoop) is fastened to the hull with #8 or #10 SS screws AND 3M 5200. Once the 5200 is set the screws are a second thought almost.

[guyrj33]

Originally Posted by thinwater

^^ He said "solid glass," so there is absolutely no purpose in removing good fiberglass. A pilot hole and self-tapper is the best practice in this case.

This is the appropriate amount of technology for the problem.

[guyrj33]

Originally Posted by Squanderbucks

The external strainer (also known as perforated scoop) is fastened to the hull with #8 or #10 SS screws AND 3M 5200. Once the 5200 is set the screws are a second thought almost.

Do NOT use 5200 on anything that may need to be removed!

[a64pilot]

I use 5200 all the time, it’s removable depending on use.
I would not install a hatch and use 5200 of course.

What sealant would you use for underwater?

[Q Xopa]

Originally Posted by Squanderbucks

The external strainer (also known as perforated scoop) is fastened to the hull with #8 or #10 SS screws AND 3M 5200. Once the 5200 is set the screws are a second thought almost.

Yes the OP said 6 x #10 machine screws. Hence I mentioned doing an epoxy plug to tap into, rather than the usual polyester hull. Others thought that was a terrible idea. Apparently self tapers are far superior. The manufacturer, and me, obviously know nothing, wasting money on machine screws.
Thanks to those for showing me the folly of my ways.

[Squanderbucks]

I vote with Hopcar. For many years I used both external and groco ARS internal strainers. When I repowered recently I could not find a place to mount the new larger internal strainer. The outfitter helping mwe with this project - asked me "when was the last time you had to clean out the internal strainer?" I said I check it from time to time but actually never did I have to clean it out. So he suggested no internal Groco only the external strainer. Says many power boats go this route now. Ok. Giving it a try.

[Cheechako]

If you actually mean the hull of the boat,... NO.
If you are talking a fiberglass part of the boat that doesn't contact the water on the other side of the fiberglass then drill and tap for a machine screw.
While you could use a blind tap and thread maybe 1/2" into the hull and find screws of a perfect length... I just wouldn't do that'
Make a wood or metal adaptor plate and glass that to the hull , then screw into that.

[CarinaPDX]

The problem with using self-tapping screws is that they crush the glass/resin mixture, and will only be good for a limited number of removals. It is far better to drill and tap, particularly if the screws will be removed from time to time. For the shear loads that a screen would experience it is unnecessary to replace some glass resin with epoxy - 6x#10 into fiberglass is going to provide ample holding. So drill a pilot hole "blind" - i.e. not through the hull - then tap. The best way to do that would be to use a set of three taps that include a bottom tap.

As I wrote yesterday on another thread I think the internal strainer is redundant if a screen is used. I like having an external screen to prevent things like jellyfish and plastic bags from getting sucked into the intake - better than having to clear a thru-hull IMHO. Whichever works for you; I just agree that both are not needed.

Greg

[Tricolor]

@finefurn you are not really considering to dril 5 absolutely non-necessary holes in your hull...? Use little 5200 and some tape to hold in place. Please use your common sense.

[zboss]

I’ve been using that particular groco strainer on my boat for about 6 years (about 2000 hours on the engine) and it has never been a problem. I have never had to remove so much as a small leaf from my internal strainer in all that time. The strainer can be opened and cleaned of anything you may need to clean out by either removing the ring and opening it or unscrewing the screen and removing it. If it were a real emergency you could easily poke a hole right through the screen from the inside of the boat.

We used a pilot hole and 1/2” bronze screws and that’s all. Between the screws and the bottom paint it hasn’t moved.

You do need to be careful that you don’t let the screen get clogged by paint.... you should go around with something small to poke the holes open. With that said, I’ve never had the engine overheat or get hot at all.

[Richard5]

Originally Posted by Jim Cate

Hey guys, he said "external" strainer, so the screws are from the outside of the hull, and there are no significant loads on the strainer.

Jim

Gulp...obviously I had something else in mind. In my defense I was left with inadequate supervision.