Thru-Hull Strainer advice ??

[Papawads]

Each year I'm replacing 3-4 OLD thru-hulls and sea-cocks with composite products, by TruDesign. These guys have a lot of fans, but that's not my question.

This year I'm doing the sea-water engine intake. This requires a separate sea-strainer to the through hull, attached independently to the hull, which I'm buying in Bronze; and it'll be one that opens for cleaning.

QUESTIONS
1. There's a strainer choice of domed round with holes, or a rectangular scoop with slots. Can I use either, or will the slotted scoop pull in water better?

2. These strainers are glued/screwed to the hull. I'm not comfortable screwing tiny holes in my hull, should I be worried?

3. Assuming I go ahead, should the screws also be bronze?

Really appreciate some guidance here!


Thanks guys

Papawads

[pcmm]

The best thing you can do here is skip installing the external "strainer". They make it nearly impossible to clean out any growth that develops. Just have a good internal strainer. If anything does grow and blocks the thruhull, you can ramrod the thruhull from inside, can't really do that effectively with the external strainer installed

[coopec43]

Originally Posted by pcmm

The best thing you can do here is skip installing the external "strainer". They make it nearly impossible to clean out any growth that develops. Just have a good internal strainer. If anything does grow and blocks the thruhull, you can ramrod the thruhull from inside, can't really do that effectively with the external strainer installed

I was trying to post that myself but my computer froze and I lost the lot

I suck straight thru the through-hull into the strainer. I motored 30 km yesterday - no troubles at all

[GordMay]

Check “Free [Open] Area” specifications, on the various Groco Hull Strainers
[Download HULL STRAINERS SERIES SERVICE SHEETs]:
APHS ➥ https://www.groco.net/products/raw-w...er/aphs-series
ASC ➥ https://www.groco.net/products/raw-w...ner/asc-series
RSC ➥ https://www.groco.net/products/raw-w...ner/rsc-series
SC ➥ https://www.groco.net/products/raw-w...iner/sc-series

[SailingHarmonie]

Originally Posted by Papawads

Each year I'm replacing 3-4 OLD thru-hulls and sea-cocks with composite products, by TruDesign. These guys have a lot of fans, but that's not my question.

This year I'm doing the sea-water engine intake. This requires a separate sea-strainer to the through hull, attached independently to the hull, which I'm buying in Bronze; and it'll be one that opens for cleaning.

QUESTIONS
1. There's a strainer choice of domed round with holes, or a rectangular scoop with slots. Can I use either, or will the slotted scoop pull in water better?

2. These strainers are glued/screwed to the hull. I'm not comfortable screwing tiny holes in my hull, should I be worried?

3. Assuming I go ahead, should the screws also be bronze?

Really appreciate some guidance here!


Thanks guys

Papawads

There is always a danger when installing a forward facing "scoop" strainer on a sailboat. it can force water into the system while sailing, with the engine off. If it can push past the engine's raw water impeller, you will flood the engine. This is also a problem on powerboats with a separate intake for a generator, the forward facing scoop can flood the generator.

This does not ALWAYS happen. So there will always be somebody who can say, "But it works on my boat." With a new pump body and a fresh impeller, and a very high rise on the cooling water gooseneck, it can resist the flow. But a worn impeller, and a nice long sail at a brisk clip, and you might be very sorry.

As pcmm has said, just skip the strainer altogether. It adds almost no value. The number of things that the external strainer will shed that would have clogged your system before the internal strainer are miniscule. (You do have an internal strainer, right?)

More important than an external strainer is some way of being able to "rod out" the intake lines all the way to the ocean. A internal strainer design that allows this, or a dedicated cleanout port will let you strip out that oyster that has taken up residence inside your intake hose from inside the boat while underway, if need be.

If you absolutely feel you HAVE to have an external strainer, the domed style is the better choice for a sailboat moving at normal sailing speeds. If you feel the rectangular format has some advantages, at least face it aft to protect your engine.

If you install one, the screws should absolutely be bronze. the screws should be short enough to NOT penetrate the hull, the pilot holes you drill should also NOT penetrate the hull. This really shouldn't be much of a problem, a properly installed seacock has a fairing/backing plate there that thickens the hull. Properly installed with a thick bead of polyurethane adhesive sealant it will not be coming off easily. And if it was to come off, you probably wouldn't notice...

[NorthCoastJoe]

As others said clear open thru hull to a strainer. I can run a wooden dowel through mine from inside the boat if I need to clear something.

From my thru hull I run hose vertically to a "T" the top of the "T" is plugged and the leg goes to the strainer. If I need to clear something I can remove the plug, that is above the water line and run a dowel through the hose and thru hull.

https://www.westmarine.com/groco-3-4...caAq0XEALw_wcB

https://defender.com/en_us/vetus-ftr...w_wcB#493=5657

[Cheechako]

I'd skip the hull strainer.
When possible I prefer a bronze strainer inside NOT mounted directly to a through hull, mounted independent with hose.

[Papawads]

I'm curious about the warning of incorrectly mounted seascoop strainers flooding my engine. Lots of people said this on other threads I've read.

I'm trying to get my head around the mechanics of that... as I know my sea-water curcuit all too well

After the impeller and three heat exchangers it enters the mixing elbow pointing vertically downwards.

The exhaust hose drops 2' (50cm) to the muffler, and out from there, to the exhaust.

So, assuming water can flow through the muffler (is that true) then if the exhaust is below the height of the mixing elbow, you should be ok; but if it's higher you're in for a heap of pain.

Thoughts most welcome