Sea Chest Grate replacement questions

I damaged our existing sea strainer in the San Blas Islands. No, I don't want to talk about it. Ours is used for:

1. Main engine/transmission raw cooling water
2. Auxiliary engine raw cooling water
3. Raw water for hyd coolers
4. Raw water intakes for 2 AC units
5. Raw water intake for H2O maker
6. Raw water for washdown pump

All the water shut-offs have zerc's for greasing, and are double clamped
All intakes go through suitable sized strainers inside the boat
We looked at replacing with the one with the removable screens, (see first link below):


but in the end decided to replace with the same type as was originally installed:


We're waiting to remove the old and install the new, either at next haulout or by diving on the hull on our next trip, while in the water. I can't do it where I am due to alligators in the water.

Three questions regarding either type of sea strainer.

1. Do you folks paint your sea chest entrance grates with antifouling paint?
2. Do you bond it somehow to the boat bonding system? If so, how? Ours isn't through bolted, so I can't just use a bonding wire/strap from the inside.
3. No one can tell me which direction the sea strainer grates are supposed to be mounted. Do the slots face FORWARD? Or is the raised section forward, with the slots aft on the strainer grate? I've been told: "Just mount it the same direction as the one you are replacing" but walking around various boat yards, I've seen them installed both ways, so just going from how ours was mounted when we purchased the boat isn't necessarily the correct orientation. I asked two parts guys at Fisheries Supply in Seattle, and they were firm on their opinion . . . . but both said the other guy was wrong . . . .

Any thoughts would be appreciated!

Scott

The grates you refer to are a good way to protect the through hulls. Good to hear you’re making it perfect, as I would expect given you thououghness.

Our DeFever had a removable grate affixed by bolts. Every year the boat was hauled, grate removed, anti fouling applied and seacocks cleaned. It was a simple robust design. The slots were longitudinal. The through bolts were bonded as best I recall, but only one of four.

I have the same style of hull strainers that you prefer.
Each haul out the strainers are removed, stripped of paint and painted with antifouling.

One fastener is a machine screw that extends through the hull and is connected to the bonding system. The rest are short screws.

The slots forming the grate face aft.

It’s worked for 28 years, I doubt I’ll ever change it.

My generator instructions specifically call for NO version of a scoop; so, if I have a grate on it, it would have to face aft. My air conditioner, on the other hand, has no possibility of having itself back flooded while off as the generator might, so I installed its grating scoop forward because I want it to always get all the water its pump can take.

It's equipment dependent, and the fact that one input is an engine tells me you want it mounted aft-facing.

Sorry I'm late replying to this. I've been having issues with TF sending me updates on threads I'm watching. I should report it to a Moderator! Wait . . . nope . . . . disregard last . . . .

I'm still waiting to replace the sea chest strainer grate. I've got it, but I'm waiting for the next haul-out, which may not be for awhile, as we're still concentrating on the house. The current grate has a "temporary" grill wired over the portion that got damaged, and is wider than I want to strain, hence the temp grill. None of the bolts through bolt, so ground wire is not possible unless I drill one bolt hole all the way through the 2" hull. I'll have to look at the access inside the engine room to see if I can easily get to a through bolt to attach a wire to the boat bonding system.
I can replace the grate with the same type of screws while we're still in the water . . . . but I need to wait until we back on the coast in salt water, as the dock we purchased (with a house) comes complete with alligators up to 12' . . . . yeah, not going into the water here.

Lots of projects still. We've totally gutted the new to us house, and are re-doing it, and I bought a used Subaru, then discovered it has a blown head gasket . . . Arrrrrghhh. Parts are here, just need to non-humid time to work on it in the garage . . . .

Then a 1980 Mainship 34 followed us home as well. That's the problem with having three docks, and 250' of dock space . . . .

Put several layers of 2000 on them. They get scratched. So either 2000 and bottom paint or nothing and dive on occasion. Paint antifouling inside and out. Prefer seachests with butterfly valve on the bottom. Don’t need strainers and can clean while in the water. Check your watermaker manual. Some are very particular about the salt water intake. Like the graco as intake faces forward and is elevated from hull. So underway no Bernoulli effect decreasing intake water pressure.