Over the years I have really grown to distrust and dislike external intake strainers of either the scoop type or the non directional round type, though I find the round type more reliable at blocking eel grass. The real danger
in these devices comes when you do have a blockage and can't get to the crud to clean it. They often require a dive over the side with a coat hanger but that does not always work.
In areas with high barnacle or muscle growth these creatures know no bounds and often take up residence in the "no mans land" hiding behind the screen
. After spending nearly three hours one day, in really, really cold water
, even with a wet suit, trying to get eel grass out of one, I vowed to never, ever have one again. Any time you dive in, your risk goes up.
To ream out an intake from inside some good pre-planning can make this a dry and easy task. It can be done in under three minutes if done right. All you need is an intake hose that can be held up higher than the static waterline and a snake. Close seacock, remove hose from strainer, hold hose above water-line, open seacock and ream out with your snake, done!
The harsh reality of external strainers is that they can become a safety
hazard, if they have not already. I find when intakes are plumbed properly there is little to no need for one, and there are better & safer straining options. You can far more safely ream out your intake from INSIDE the vessel if you don't have an external strainer and this can be a huge safety
margin when you don't have to physically get into the water. In just one season here in Maine
I was in the water three times with a coat hanger...
Some reasons why I don't like them....
Beyond these photos many boat yards, some builders, and DIY's install the scoops style strainers backwards on sailboats. Many a sailor have actually caused their engines to become hydrolocked and dealt with water in the cylinders because of the improper installation
of a scoop style strainer. If a scoop strainer faces forward you risk physically scooping sea water up and over the siphon break then filling the exhaust
and eventually the cylinders of your engine
with sea water. This is not healthy for the engine
or your own piece of mind.
This strainer, like many out there, is another potentially expensive mishap waiting to happen. All it takes is some rough weather
and a good surf down a wave to fill your engine with salt water
. Facing them backwards is better but can also add unnecessary vacuum on the raw water pump
. Sailboats should ideally have round, non-directional strainers, not scoops, or my favorite, none at all.
If you feel you absolutely must use one please make sure it can be opened. This one is made by Groco and Hamilton Marine
External strainers are absolutely not clog proof or growth proof. If they can't be opened it may be next to impossible to clear without removal
of the external strainer screen
. The worst of the external strainers are where the strainer is actually integral to the thru-hull fitting, and can't be opened, or even removed, without physically breaking the sealant
bod and backing the whole unit out of the seacock......