Strainers on 312

[BobsBoat]

Does anyone know where the strainers are?  I have been told there are 4 (one for each engine and one for the AC and the last for the Generator.

[frodo13056]

Generator strainer is in the engine compartment - just look for a seacock / strainer that runs to your generator.
AC strainer is located under the aft berth cushions - you have to lift the cushions on the startboard side, then you'll see a white drop in access cover - lift the access cover and you'll see the AC cooling pump / strainer and seacock.
As for engine strainers - most of the time, seawater is picked up from the lower units. If you do have seawater strainers for the engines then someone added them or your boat has inboard propulsion (no out drives) and those strainers should be fairly obvious in the engine compartment.

[BobsBoat]

Thanks.  Friends who have larger boats mentioned I should have engine strainers but I could not find them.  I am going to look for the Generator and AC ones tonight and change them if necessary.  I assume they can be changed while the boat is in the water?

[frodo13056]

Strainers have a removable metal screen that basically filters out large chunks from the water - thus the "strainer" effect.
1) CLOSE the seacock FIRST!! The seacock valve handle should be at a right angle to the valve to be closed. The valve handle is in-line with the seacock to be in the OPEN position. Usually there are markings on the valve and handle.
2) VERIFY that the seacock valve is closed.
3) The strainer is composed of 4 items:
      a) Plastic body - a clear plastic body that houses the metal strainer. It screws on / off.
      b) Plastic top - this piece is where the seacock inlet / strainer outlet is.
      c) O-Ring gasket - fits between the body and the top. You'll see it when you unscrew the plastic body.
      d) Metal screen - this is the actual "strainer".
4) Remove the strainer body making sure that you do not lose the O-Ring gasket. You'll lose a bit of water but it should only be a little. If lots of water comes out of the top, the seacock valve is leaking by or not fully closed. If you have trouble removing the plastic body, use one of those rubber strap wrenchs and be careful since it it plastic. Remember that you are working on an upside down rotation pattern so make sure you are going the correct direction when removing.
5) Pull the metal strainer out - it fits in a grove in the plastic body. Clean strainer with brush and clean water.
6) Re-install strainer in groove in plastic body - this can be a bit of a pain so take your time and do it right.
7) Make sure the O-Ring gasket is in good condition. If not - replace. They can be hard to find so be careful with the one you have! Re-install O-Ring in plastic body.
8) Re-install strainer body to strainer top. Only go hand tight plus a little when tightening.
9) OPEN seacock. Check for leaks. Sometimes it's best to crack open the strainer housing to let it fill with water once the seacock is opened. This will help prevent an air lock situation where air prevents you from getting solid water back to the Generator or AC unit.
10) If this is done to the AC unit, most likely you will need to re-prime the unit - there a several ways to do this. Do a search on this forum and you'll see the variety of ways that folks re-prime the AC unit.

It's not as hard as it sounds - but take your time.

[jjlovett]

Couple of other notes - sometimes the screen is a bit tough to get out - just know that it is removable.

Also - make sure you keep track of that rubber o-ring gasket - yes it can be replaced but whichever system it is will be out of commission until you get a new one (if you misplace it). It'll be a slow to fast leak depending on the thread tightness of the strainer.

[alswagg]

Another note to keep on tab.   Mercruiser Horizon engines, closed cooled engines, have dual water pick ups.  One going through the outdrive and another through the hull.  On these engines a sea water strainer is added inline of the incomine water supply.   On Volvo Ocean series, a sea water strainer is also installed.  These models have through the hull water pick up also.  Al