Raw Water Strainer Opinion

rwidman said:

And if you don't your engine overheats and the impeller melts.

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No, you just position the valve so it take a suction from both sources. Since the strainer is below the waterline air pressure is less than sea pressure. Modulate the position so that there is always some water entering the engine driven pump. The pump has to run dry before the engine will overheat, not the other way around.

Rick, I like what you said about heading for the beach or another boat. If you are taking on water.
Spot on.
The first thing I would do if I was taking on water.
Ground her.

I don't have an inboard strainer. All I have is a scoop strainer on the outside of the boat. It seems to keep out the seaweed and grass. Never had a problem with anything else getting in. Must be something about boating in pristine water no trash.
Been running her for 10 years now with nary a problem.
Butt. I have one, never installed.
I'll get around to it one of these days.

Sd

" Modulate the position so that there is always some water entering the engine driven pump."

Easier said than done while the S is alliding with the F.

I am also curious as to how you determine that the engine is getting enough water.
Of course, if it is the through hull itself that is the cause of the leak, it's all moot. And if it is another usual suspect, the shaft log, and your through hull and strainer are located adjacent to it, the working conditions for proper "modulation" are, shall we say, challenged. Especially for you guys who have to go diving into a confined ER to get to this stuff. I have absolutely the most ideal access you could ask for, and still have these qualms.

As the tagline, probably a Steven Wright quote, of a guy on another forum I frequent says: "I want to live in Theory. Everything works there".

Wouldn't it be simplest to just install the biggest electrical bilge pump you can find and plumb it overboard? Or multiple bilge pumps? On seperate batteries? And back this all up with a manual pump.

We can't account for every possibility or we would be wearing crash helmets and goggles while driving our cars. It's a matter of risk management.

Flushing a heat exchanger-cooled marine diesel with fresh water is not necessary. Every few years here in Florida, I pull the oil coolers on my engines and plug the oil ports before plunging them into a bucket of muriatic acid, just like the radiator shop I used to take them to did. The engine coolant heat exchanger is tougher to remove due to the necessity to dump the engine coolant; so I pour muriatic acid into its 5/8-inch zinc holder hole. By the time I screw the plug back in and start the engine, the little bit of acid in there has done its job.

What concentration of acid do you use?

Too much acid and you LOSE your concentration

Wouldn't it be simplest to just install the biggest electrical bilge pump you can find and plumb it overboard? Or multiple bilge pumps? On seperate batteries? And back this all up with a manual pump.

Simplest is a belt of the main engine and a 2 inch Jabsco with an electric clutch.

This pumps over 100 GPM with 2 inch hose.

Easy enough to fit it with a Y valve and a deck discharge for washing mud off anchor chain easily.Every anchor up would be a bilge pump safety check.

Obendorff makes similar electric pumps , but the batt bank would be thousands of pounds!

caltexflanc said:

I am also curious as to how you determine that the engine is getting enough water.

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It isn't overheating is a good indicator

"I want to live in Theory. Everything works there"

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If you think about what can go wrong, plan on how to deal with it and practice doing it you might surprise yourself.

The alternative is to sit there and cry while your world falls apart around you. It's your boat and if you have passengers it is your responsibility to be able to deal with the situation you took them into.

None of the stuff I wrote is theory, it is a practical and frequently performed technique to keep a pump running when the source is less than its capacity. If the source is larger it buys time and that is the best thing available - don't let your "qualms" sink your boat or hurt an innocent passenger.

Keith, I get the acid from the pool supply store and use it straight out of the bottle. I foams up real good in there as I put the zinc holder cap back on. When done, I put a zinc in the holder.

Yikes! I diluted same acid by half and tried that on my genset heat exchanger. It instantly dissolved the gasket. I've shied away from doing it in situ ever since.

Yea... me too. I used about a shot glass to a gallon of water and it cleaned my genset exchanger nicely.

There are lots of things muriatic won't attack. It had no impact on the rubber from the inner tube I had cut to make a gasket on one end of my heat exchanger.

And the rotten egg smell is second to none!