mcollinstn

Here's something I've come up with that may be of help to some of you guys as well.

My cruiser has all of the water intakes for the engines and genset mounted at the center of the vee which puts them where they get the hell knocked out of them by every log in the lake, and they vacuum up bushels of silt when I go in some of my favorite coves which have shallow entrys.

I check my strainers weekly, but they tend to go from clean to full very quickly depending on where I've been traveling. My A/C intake is mouted offcenter in a prop tunnel and stays clean seemingly forever.

Now we get to the problems I have with my arrangement. My Caterpillar raw pumps are fairly accessible and the impellers are huge and very durable. They do not cause me a lot of problems. My Westerbeke genset is mounted in such a manner that I truly CANNOT remove the raw pump for impeller replacement and cannot replace the impeller without removing the raw pump. In order to service the raw pump on the genset I have to utilize my 12-yr old AND a skinny flexible friend, aling with some cutdown box-end ratchet wrenches and beer. My forearms simply will not fit into the space necessary for the work. The raw pump it gear driven and does not lend itself to relocation for easier access (which was my first desire).

The more I thought about it, the more I thought that an alarm indicating a restricted strainer may be a better solution.

Here's what I've decided to do.

I'm going to put a bronze tee on the line going from the sea strainer to the raw pump. On that tee I am going to place an adjustable vacuum switch. I will adjust the switch so that it will remain closed at the intake suction level generated with clean thru hull scoops and a clean strainer. When the intake line suction rises (as it will do with a restricted intake or strainer) then the switch will open. I can tie this switch into the "shutdown" loop on the genset. This will shut it down when the strainer or intake becomes restricted, thus saving the impeller and allowing "normal" service life from it.

Some of you guys seem to have troubles with your LWP Bravos sucking sand and silt. This addition after your strainer may prevent some of the problems you have been having.

mcollinstn

What?

nobody's got any feedback on why this shouldn't work?

rjcardinal

When I filled my engine with sand I knew exactly what happened right when it happened. The alarm wouldnt have saved the day for me. While on plane I drug the LWP lower unit through a sand bar. I shut it down as soon as I felt it. The water pressure gauge went to zero immediatly. In less than 3 seconds it filled the cooling system to the power steering cooler with sand. The hose comming from the sea pump was packed so tight it felt like it was a piece of rubber coated steel. To have an alarm go off would have just made me more angry.

Ron

paradigm shift

Sounds like it should work to me. You can get switchs with a reset or trip alarm so you will know that is why your gen set is not running. You may want to put a gauge in the line for some testing first to see what switch will work.

mcollinstn

I'm going to use an adjustable switch. I can back off the setting till it makes the switch then go back a little.

I gotta do something. I might also try one of those jetboat sand traps. Still gonna fab up the alarm cause when the genset gets junk in it, the Cats do too. That way I can clean all the strainers when the genset alarms out..

Boatfixr

Take a look at this great product that is adjustable for various flow rates.

http://www.flowdetector.com/products.htm#flow

mcollinstn

Ok, looks good, but I'm honestly a little hesitant to put a PVC piece in a section of plumbing that is below the waterline.

The only section of the loop that is above the waterline is the "hot" end of the loop, and once again, I am hesitant to add a piece of PVC to the hot side, too.

Maybe I'm too cautious.
Any thoughts about PVC below waterline???

paradigm shift

I would agree on being cautious. Although my Bravo infeed plumbing is some kind of plastic / PVC including the raw water pump and they sit below the water line!! You could run the screw in probe (model 400) and insert it in metal piping.

I would go with your original plan and use the switch if it were me.

mcollinstn

Yeah, but "some kind of plastic" and PVC are two different things in my mind. I still run the Bravo plastic raw pump and i have no idea what kind of plastic it is.

I've also heard of some corrosion issues on 496's on a brass fitting that was screwed into an iron manifold. Warranty replacement for those claims was to substitute a plastic fitting instead.

I know that Marelon is a plastic that is tough, corrosion proof, and everlasting.

I've just seen too many pieces of weathered PVC pipe that fall apart in your hand to feel good about it.

A freshwater fitting will dump the contents of your freshwater tank in your hull if it breaks.

A seawater fitting will dump the contents of the sea into your hull if it breaks.

Hmm

(raising three boats off the bottom of the mud will make you cautious)