Installing Strainer for AC

[Goofeyfoot]

OK, so here are a few preparatory questions:

First, should I use 5200 or should I use Epoxy to hold the plastic board in place?

Two, What surface preparation would you need to do to make sure the adhesive sticks?

Three, how would you clamp the board while the adhesive dries?i Seems like you'd have to load up with scrap wood or something and use shims to maintain pressure?

Three could I install both pump in the strainer on the same board?

Four, do I need to repair the broken pump mount, or can I just mount the pump on the board?

Sorry to ask so many questions, but I'm trying to get everything thought out before proceeding.

Thanks again.

Michael

[redsky49]

Wait until you have all the parts on hand.

All the strainers I am aware of require a good bit of vertical clearance for service, and require a vertical installation. You will need to periodically clean the basket. The inlet to the strainer, and the pump, must be below the waterline.

Any hose - prior to the strainer - that loops up and back down will create an air trap. Keep the hose level or continuously sloping from the sea cock to the strainer. You will still likely need to burp the system at start up. Easiest way is if you can just loosen the top of the strainer.

Hose is (relatively) cheap. Position the components, allowing for future maintenance requirements, and route your hose as circumstances allow.

And yes, double clamp connections, preferably with ABBA stainless clamps which will outlast the typical ss hose clamp.

As mentioned above, verify the existing thru hull, which appears to be a ball valve, improperly installed, rather than an approved sea cock.

[Goofeyfoot]

Could I go ahead with the strainer and then fix the ballcock in the winter when I am out of the water?

[rourkeh]

Once you get the strainer installed you had better flush the A/C unit with acid, I can only imagine the amount of crap that has accumulated in the coil without a strainer. Surprised it is working at all. Also replace all the hoses if more than a year old.

[a64pilot]

Idea of glueing a piece of wood as a mount is to not drill holes in the hull, a 3/4" piece of marine grade plywood or exterior plywood if Marine grade is unobtainable and use 3/4" SS wood screws to hold the strainer to the wood, 3/4" screws as the strainer's flange will keep the screw from bottoming out, yet get them most grip.
To me 5200 is way strong enough, yet has some flex and I think holds very, very well.
And I don't have to mix it, but uncured epoxy is easier to clean off than uncured 5200, so pick your poison.
It's been proven that one drop of 5200 can coat your entire boat, and the upholstery in your car.

[Goofeyfoot]

Could I use that pvc plastic trim instead of wood? Plastic won't rot. What do you think?

[a64pilot]

Never tried plastic, I assume your talking Starboard?
I don't know how well it would adhere, but if kept decently dry Marine plywood lasts a long time, one holding my engine strainer has been doing so for 30 years, one corner is a little soft cause strainer was leaking, might need replacing in ten years or so at current rate.
With 5200 just stick the board to the wall and a piece of painters masking tape will hold it in place until the 5200 cures, I glued in a half dozen three by three pieces on the hull on the chain locker so I could attach the windlass wires when I installed that for example.
Starboard would be neater, but a 3/4" piece or 1" piece's price may surprise you.

[Goofeyfoot]

Ok I will go with Marine ply. Do you coat that with something before using? It will be wet almost all the time.

And 5200 would hold the weight of the pump?

Thanks so much for your assistance. It is very helpful.

Michael

[a64pilot]

I have painted the wood with 5200, seems to work well, it's about the consistency of toothpaste, I used a disposable acid brush.
5200 will I am sure hold me, I have never heard of a complaint of 5200 having a weak bond, it's usually "How do I get this thing off".
Now I don't have experience with epoxying in the board, I can see how if you soaked it in thin penetrating epoxy and let that cure before mounting it, that would be a better waterproofing than almost anything.
I go the 5200 route as it's easy and although it is work, I can remove it at a later date

[redsky49]

Starboard is difficult, if not impossible, to successfully glue. Typically it is mechanically fastened.

If the mounting location of your equipment pad will indeed be continuously wet, I would rethink the use of plywood.

First, I would see if there are alternate locations where the pump might be mounted. While strainers typically are installed vertically, pumps frequently will have several possible mounting arrangements. That looks like a March pump you are using. Get the model No. and google the March web site to see how it might be mounted.

If you are committed to a wet location, verify that the pump is certified for immersed duty. I would use something other than plywood for mounting unless you first either epoxy saturate the plywood or encapsulate in fiberglass. A couple coats of paint are acceptable for occasional moisture, but are inadequate for continuous immersion of plywood. Look at how plywood skiffs are built, for example.

From your pic, it appears that some of the hoses are double clamped, others are not. The hose clamps are starting to show corrosion and are a couple sizes too big.

I cannot see a backing plate for the thru hull. That would be my biggest concern. Might be there, and I just can't see it from the pic. It takes very little lateral pressure to break an unsupported ball valve free from the hull. Traditional sea cocks are far more sturdy. Check this carefully.

Assemble all the pieces and spend some time with the little grey cells, arranging the installation to meet all your requirements, including future servicing/replacement.

I would toss all the old hose, just so you won't feel compelled to mount the components to suit the existing hose. If it is wire-reinforced (it doesn't appear to be), then there will likely be corrosion of the exposed wire and that can compromise the strength of the hose. This is a less demanding application than an engine, so, in my opinion, a fabric reinforced hose is adequate, and will be easier for you to install.

Maybe clean and paint the area prior to installation??

[Goofeyfoot]

Ok that clears up a lot of issues. But what other material would I use if not plywood?

[JBPohle]

I've got 4 AC units that run year round. We live aboard in FL. 18 year old boat with NO basket strainers. It's got a strainer (at least a plate with 1/8" holes on the through hull inlet. Outside of the hull.). Seawater pump serves two units each. Yep two pumps. Never ever had an issue with plugging. Only issue is a slow build up of slime that we back flush out with a hose every 4 months. Neighbors clean filter style strainer here very often. The filter style seem to collect all kinds of small plant material a plug up. I'd guess the external strainer just self. Leans when the pump is off and there is no suction. Food for thought.


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[Goofeyfoot]

Interesting. I don't know whether I have an external strainer.

Will check.

How do you perform the backflush?

Thanks.

Michael

[thinwater]

A few more things:

a. Install a valve between the strainer and the pump; close when cleaning the strainer and the AC plumbing will not drain in the bilge when you open the strainer.

b. The pumps size must be matched to the AC unit. Manufactures say that over sized pumps can cause erosion and failure of the cooling pipe. Don't go bigger "just to be safe."

c. Yes, you need an external strainer. I've sucked fish in my AC before and they jammed before the strainer. Messy. AC is the worst for this because other intakes are either not continuous (head) or are used underway (engine).

d. Don't forget winterizing. Install a tee for adding glycol, while you are at it.

e. The best material, IMHO, is what the boat is made of; fiberglass. You can buy precast boards.

f. The idea of external-only is appealing, but I am uncertain. I have an external strainer and the internals strainer still plugs up every week or so in heavy weed areas. This may also depend on the external strainer style and the local weed. The grass here will go though a very small hole if it hits end-wise.

[a64pilot]

A backflush is just that, disconnect the hose from the exit thru hull, connect a garden hose to the hose and with the AC off, let the water flow, flushing out the system backwards from normal flow, if something got stuck in there, this is an excellent way to blow it out.
I take both the exit hose and the hose that feeds the AC before the pump and stick them in a five gl bucket. I have a couple of extra hose to make this happen.
Fill the bucket with one gl of Muratic acid and the rest water, turn on the AC and let the mix circulate through the AC for a couple of minutes, water will heat rapidly some form the action of the acid and some from the AC of course.
Disconnect hoses, dump acid overboard and run the AC normally.
You'll be surprised how much "stuff" flushes out almost immediately when the acid mix hits it.


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