Hull drag - Bronze water scoop intake

[reinax]

Hi,

I have a 30ft raceboat with a 2GM yanmar inboard with a 2 blade shaft drive. We are going through great lengths optimising the performance of the boat. This includes having a meticulously smooth hull. That being said, we've got this bronze old water scoop for the water intake of our engine. Obviously, this bronze thing sticking out is not going to make me go faster. Do I actually need it? Could I just do with a hole and a filter? I don't sail in a place with lots of seaweed or other stuff in the water. Any advice on what I could use instead?

Please advice

 

[El Borracho]

Remove it. High drag and zero style points. Better that whatever comes along to clog the intake continues to the strainer where it can be removed at leisure. On the recommendation of the manufacturer I had a scoop on the watermaker intake. It made a sweet home for the critters that required swimming and much fussing with a probe to clean. Never have had any issues with the plain old easy to clean holes (Which can be cleared from inside, underway, if one is bold.)

 

[longy]

^^ Intake screens not needed. Over many, many days of being on boats I've only had an issue twice. Once sucked a plastic bag up the intake, once sucked in a fish. Easy to diagnose, easy to fix (the fish was a bit messy)

 

[Zonker]

Remove and make sure you have a strainer on the INSIDE of the boat that you can easily get to to check/remove/clean.

 

[Zonker]

Pro tip: stop engine, close seacock before opening and cleaning strainer

collary: open seacock after strainer cleaning.

I like the Vetus ones. They unscrew easily.

 

[steele]

Agree, those external scoops/filters collect stuff like barnacles, I have seen a few restricted by sloppy bottom paint jobs.
I also like the vetus ones and have one on my boat. I dont like that they look like tupperware, but mine has held up fine, once I found a completely intact shrimp inside.
If possible install the filter with a strait shot to the through hull. This allows you to use a flexible wire to clear obstructions that don't make it to the filter by just uscrewing the lid. Since I have a saildrive I can't, but Panope who posts here off and on has a nice set up with a vetus filter.

 

[longy]

Also - install the filter so the lid is just above the waterline. Makes servicing a lot easier/cleaner!! Impellor raw water pumps can easily get rid of the small amount of air

 

[FlyingCircus2]

I agree with zonker and the others that you can use an internal filter.

I'm surprised that a race boat would have a scoop at all. Does it look like it was always there? I'd take a bit of time to find out if the previous owner knew something we don't know, but I don't know what that thing would be. Is it in line with the propellor and keel? It's probably not as big a deal if it is.

One thing I would recommend in August when the water is warm, is to practice a dive to your water intake. Sucking in a plastic bag really... Umm... Sucks. They don't always make it to the filter.

 

[longy]

Poke them out with a long screwdriver (or similar)

 

[Zonker]

I have collected the following in a sea strainer for my watermaker:

baby shrimp
small fish (deceased)
jellyfish
bits of wood
bits of weed
I suspect you get a lot more when the boat is stationary and some innocent fish comes along and says "hey what's this little hole... fuck!!!"

In the engine sea strainer, more like eel grass and bits of small wood

Do it this way and you can poke the inlet

 

[reinax]

Thank you all, for your insightful and prompt advice. I acted accordingly and taken off the bronze scoop. It'll be difficult however to install a filter above the waterline. Since i then cannot clear the inlet line (with a flexible wire for example) i might look out for a flush tru hull that has some sort of screen (and avoid a plastic bag blocking the seacock). I've also heard of flush tru hulls that actually close up the hole and become completely flush when not in use. Anyone know which brand sells such a thing?

 

[IStream]

Don't put a screen on the outside, that's asking for trouble. Just because you can't put an interior strainer above the waterline and/or directly above the seacock doesn't mean that an interior strainer isn't still 100X better than a scoop or exterior screen, which is guaranteed to clog up even faster than your scoop.

Mount the interior strainer wherever is most convenient and just close the seacock before you open the strainer to deal with the fact that it's below the waterline. Rather than going with a flush thru-hull, I'd prioritize making it larger. The larger you can make the thru-hull, the stronger the valve will be and the less likely the (wider) hose will be to clog with anything.

 

[Zonker]

It doesn't have to be above the waterline. Below the waterline works just fine. Just means a little more water spills into the bilge when you open it.

 

[SloopJonB]

I've never had one mounted above the W/L and never had a problem.

 

[El Borracho]

The ability to clear the thruhull by poking via the strainer is a sweet trick. But often not possible. Certainly not a requirement. Pulling the hose off the strainer or seacock is not a big issue, but have a sponge handy. Anything short of a mussle can likely be blown out of the plumbing. Presence of a mussle indicates seriously casual maintenance, vs. a plastic bag. Avoid any additional inline fittings, especially elbows.

Having the strainer more than a few inches above the sailing waterline risks cooling failure. Siphons are one of those things that are brilliant in theory but unreliable in practice.