Raw Water External Strainer Debate

[Bill O]

Originally Posted by wingless

Here are mine, before I switched from protecting my underwater metal using barrier coat / bottom paint / Prop Speed to Rustoleum. The Rustoleum is waaay better.

The screen on these APHS strainers could be pointed to the rear for sailboats to avoid hydrolocking the engine.

Mine have never required opening the door while floating for cleaning.

May need to try the Rustoleum. Do you use that on all your running gear instead of a barrier coat?

[wingless]

Originally Posted by a64pilot

I bring this up as some may not realize it, but external strainers are not attached to the thru hull in any way, they are held on by screws that screw into the hull.

When I installed my external strainer one of the mounting fasteners is a long bolt that I used to bond that bronze to the rest of my bonding system. All the other fasteners are screws.

[wingless]

Originally Posted by Bill O

May need to try the Rustoleum. Do you use that on all your running gear instead of a barrier coat?

Yes, I stripped everything down to shiny bronze, almost all was removed using a paint scraper, then every bit of underwater metal now has Rustoleum. Hands down this has been the very best solution I've used for my metal.

[rslifkin]

Hmm, maybe I should look into those APHS strainers when I re-do my setup. I've seen other positive reviews of them. And they seem like they'd be hard to really clog, so a blast of reverse may be enough to knock any grass and such off the surface of them.

[wingless]

Originally Posted by rslifkin

Hmm, maybe I should look into those APHS strainers when I re-do my setup. I've seen other positive reviews of them. And they seem like they'd be hard to really clog, so a blast of reverse may be enough to knock any grass and such off the surface of them.

When I finish using my engines and I am flushing out my raw water cooled exhaust, with fresh water, soapy water and Salt Away, part of that process is also to back flush all of those products through the intake, flushing the strainer, through hull and seacock.

When I dive the boat I wipe off any external screen growth.

[a64pilot]

The scoop isn’t going to to slow you down by any measurable amount, the drag is tiny.
However if you sail fast enough the scoop will function as designed, and will scoop water into the engine and fill the muffler and hydrolock the engine.
An impeller pump may allow water through depending on where the vanes stop and how perfect the seal is.
If you always close the thru hull. Of course then this can’t happen. Just don’t ever forget.

[a64pilot]

The RSC Groco strainers that I have
https://www.groco.net/products/raw-w...ner/rsc-series

[mholtzberg]

I was on my friend's 35.5 and we got an overheat alarm as we trying to leave Charlotte Harbor at 11pm. we shutdown the engine and dropped anchor. The sea strainer was clogged with grass and checking the flow into the strainer we were clogged. I was able to remove the hose off of the seacock so we could jam a screwdriver through the seacock and we were able to clear it... We don't know what it was but, it was our last resort before jumping in the water and clearing it from the outside. Not a good idea in the dark.

[Cheechako]

It's not entirely uncommon for a plastic bag, or a small fish to get into the intake. The external strainer avoids this.

[finefurn]

Our marine and the river leading to it has a lot of loose seaweed floating around, My RW thru hull and Strainer were constantly getting plugged by sea weed, resulting in overheating. I Last year I installed a RSC Groco external strainer,( Same as a64 pilot). Its only been a year,and so far no clogs and trouble free. If your considering a external strainer I highly recommend this one.

[jhulmer]

Originally Posted by wingless

Yes, I stripped everything down to shiny bronze, almost all was removed using a paint scraper, then every bit of underwater metal now has Rustoleum. Hands down this has been the very best solution I've used for my metal.

Are you referring to Rustoleum zinc coatings?
Jim

[wingless]

Originally Posted by wingless

The APHS screen exterior is easy to clean while floating. My underwater metal is protected w/ Rustoleum Cold Galvanizing Compound, including this screen, with good results.

Originally Posted by wingless

Yes, I stripped everything down to shiny bronze, almost all was removed using a paint scraper, then every bit of underwater metal now has Rustoleum. Hands down this has been the very best solution I've used for my metal.

Originally Posted by jhulmer

Are you referring to Rustoleum zinc coatings?
Jim

Yes, link already provided above.

[stormalong]

My boat was built with a Marelon flush (flat) strainer on the engine intake. It also has a Groco strainer inside. The Groco is almost superfluous as it seldom catches anything. Although it has never caused a problem, when an adjacent through hull became available due to the removal of water cooled refrigeration I added a second flush strainer Y'd to the first (second seacock of course).

Over the years I converted the head intake and deck washdown pump to outside strainers too. Solved problem of getting grass and jellyfish in the head.

Never had a problem with any of them clogging up. Boat is antifouled about once every four years and hull is scrubbed once a year in the spring.

[a64pilot]

You go four years between bottom jobs and only clean once yearly, your in an area of nearly zero growth, so barnacles growing in your thru hull is unlikely

[stormalong]

Originally Posted by a64pilot

You go four years between bottom jobs and only clean once yearly, your in an area of nearly zero growth, so barnacles growing in your thru hull is unlikely

There are plenty of barnacles growing on pilings around here. Maybe it's just good bottom paint.