Post fresh water rinse....

[oscarvan]

So the buildup in our raw water systems necessitating the acid flush is obviously a byproduct of mostly (alkaline) salt water.....

Just like outboards a fresh water flush after running would not be a bad idea. But where to connect the hose. I have a 1/2" NPT hole in an elbow in the intake before the raw water pump. It is there to connect a winterization hose, after removing the impeller, I assume.

Now I know that a water hose is not enough water for the cooling system with the intake closed, or is it OK for a minute or so? The impeller wouldn't run dry but there wouldn't be enough cooling. But if you wait a little so it cools and then do it it wouldn't heat up. The other option is to turn on the hose and turn the engine over with the stop button depressed so it doesn't start. No fuel would be entering the system. Ideally of course I would put the hose right after the pump but there doesn't seem to be a good spot....

Thoughts? Accepted practices out there?

[Pascal]

I don’t know how much benefits a fresh water flush really brings to a marine diesel. Is it even worth it? If you were to inject the pressurized fresh water before the raw water pump, wouldn’t the pressure be enough to push the impeller vanes enough for water to flow thru? Assuming the sea cock is shut of course...

Maybe worth it if the boat is going to sit for months otherwise... I doubt it

[oscarvan]

If you were to inject the pressurized fresh water before the raw water pump, wouldn’t the pressure be enough to push the impeller vanes enough for water to flow thru? Assuming the sea cock is shut of course...

Interesting. Easy to find out, as the input is there.

[racclarkson@gmail.com]

I don’t know how much benefits a fresh water flush really brings to a marine diesel. Is it even worth it? If you were to inject the pressurized fresh water before the raw water pump, wouldn’t the pressure be enough to push the impeller vanes enough for water to flow thru? Assuming the sea cock is shut of course... Maybe worth it if the boat is going to sit for months otherwise... I doubt it

Tap should be after pump discharge. I’ve got 85 psi of water pressure and that has no impact on the impeller. The seacock position is immaterial; no significant water gets past the pump. If you’re worried about fuel coolers, intercoolers, etc. failing from corrosion, then a freshwater flush can only help.

[oscarvan]

So how about the original question of running at idle for a minute on water hose alone?

[jim rosenthal]

I don't know about that, those engines use a LOT of seawater, even at idle.

[racclarkson@gmail.com]

I see no need to run the motors to get a good flush.

[Scarlett]

I have been thinking about doing the same system with a hose and not running the engine, however my ‘74 53MY has fairly tall mufflers aft and would the water get through them without exhaust pressure pushing it out and would the top of the muffler be above the engine. Not sure?, John

[racclarkson@gmail.com]

John,

So how to tell is to shut down the motor and see how long you can detect water still draining out the exhaust. Inversely, if you crank a motor and it takes 10-15 seconds, or so, to get water out the exhaust, I think you can safely conclude the mufflers are draining to their design plan.

In my case, I can observe healthy drainage after closing the freshwater flush valve. The amount of time appears to be roughly the same as after an engine shutdown, which is just how long it takes the HE and piping to drain down.

[oscarvan]

So if we have to be after the pump the next, and last, place to put it and reach everything is here....Anyone have that tube they are willing to part with so I can play with it?