Cummins Marine Diesel Repower Specialists Forums General Discussion Is fresh water flushing worthwhile?

  • Creator
    Topic
  • #14546

    David Marchand
    Participant
    Vessel Name: Atlas Pompano 23
    Engines: Yamaha 70 hp 4 cylinder/cycle
    Location: Punta Gorda, Florida
    Country: USA

    Years ago, following Tony’s recommendation, I hooked up fresh water flush fittings to my engine’s strainer and started flushing religiously. Within less than a year I noticed that the engine zincs were holding up much better; in fact after three years they are still going strong. I also believed that I was reducing corrosion on my raw water metal components, particularly the after cooler. Tony has implied that you can double the interval between after cooler servicing if you flush with fresh water.

    But now I have doubts about both zinc wastage and the impact on the after cooler with fresh water flushing. Here is why:

    A bit of research indicates that zincs in fresh water form a protective coating that doesn’t allow an further wastage. That is one reason why my zincs have lasted for more than three years. But a question remains- does that protective coating also mean that the zinc doesn’t do any good when you go cruising for  a few days in sea water? My guess is that the zinc does not do any good.

    Further research indicates that for both fresh water and sea water use you should use aluminum anodes. These are available from boatzincs.com for hull anodes but not engine pencil zincs. Performance Metals is the only manufacturer that I have found for aluminum pencil zincs which they call Navalloy. Unfortunately Performance Metals doesn’t sell to the public, a review of some of their distributers comes up with only one that has aluminum anodes and these are for outboard engines, and finally Performance Metals hasn’t responded to my email asking where I can buy their pencil zincs. I can only conclude that the average boater will have a hard time buying them.

    But what about the benefits to the after cooler of fresh water flushing, which was the primary reason that I started doing it. After cooler corrosion is real and results in failed after coolers and possibly failed engines if it isn’t corrected. My own limited experience indicates that corrosion starts on the aluminum housing surfaces, probably due to condensate combined with salt air corroding the aluminum. Fresh water flushing will do nothing to stop this.

    I have reviewed perhaps a dozen pics of corroded and failed after coolers and they all have extensive aluminum corrosion. Some also have minor corrosion on the bronze tube sheet which is exposed to sea water, but I suspect that it is caused by the o-ring seal failing and then galvanic action between the aluminum and bronze causes pitting on the bronze.

    So, if zincs won’t work with fresh water flushing, you can’t buy aluminum anodes, and it won’t help prevent after cooler corrosion- then why do it?

    David

     

    1 user thanked author for this post.
Viewing 20 replies - 1 through 20 (of 55 total)
  • Author
    Replies
  • #75491

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    Hi all, first post. Apologies for reviving an old thread, but I’ve tried multiple searches and cannot find the Tony’s Tips article on fresh water flushing. It’s referenced in the “marine age” article but no link and I have had zero luck finding it.

    Are you looking for a “how-to” ? There is no such instruction as one size does not fit all. Many many variables with some of the key components being your seawater intake plumbing, your exhaust design and what you want to do (or not have to do) when back at the dock. Search away on the forum for multiple setups our members here. When you have a plan together and want some feedback, post the details here or start a new topic.

    1 user thanked author for this post.
    #75476

    Leander Landrum
    Participant
    Vessel Name: 2001 Tiara 3500 Open
    Engines: 2x Cummins 6BTA 370
    Location: Tacoma WA
    Country: US

    Hi all, first post. Apologies for reviving an old thread, but I’ve tried multiple searches and cannot find the Tony’s Tips article on fresh water flushing. It’s referenced in the “marine age” article but no link and I have had zero luck finding it.

    #41665

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    The ignition key on the seacock when closed is my M.O. as well.

    #41664

    David R Flamer
    Participant
    Vessel Name: Tax Break
    Engines: QSB5.9 380
    Location: Marina del Rey/Channel Islands Harbor, CA

    When you are committed to the flushing process at end of each run of the boat, and the flushing becomes part of the routine of operating the boat, opening the seacocks won’t be a problem.

    Nonetheless, I have two large DO NOT START placards on the dashboard when the seacocks are closed.

    Further, when the seacocks are closed, I hang the ignition key off of one of the seacock handles. That way I have to open that valve before I get the key.

    It’s a system that does work.

    #38527

    Brian Katz
    Participant

    Pre-Pump Flushing

    My boat is equipped with Sherwood pumps which are prone to leak. I’d have to assume that flushing from the strainer would ensure that raw water pumps were “washed” and would help to reduce marine growth in the sea strainer itself. I can tell you that my isolators would have loved it had the prior owner flushed but such is life.

    I’d be apprehensive to close a seacock as I have seen captains forget to open them and burn up a perfectly good impeller. Even after pulling in “pink” for the winter I immediately open them back up.

    The goal is keep the impeller cool and lubricated. Don’t advance the throttle when flushing and running on hose water is fine.

    #38401

    Mike Mason
    Participant
    Engines: Qsb 5.9 380
    Location: San Diego
    Country: Us

    Yup

    Our system is very simple. We used the port on the water pump after the impeller. From there we run a hose to each port and starboard lazarette

    At the hose end we have a simple pvc shut off and a garden hose hook up.

    After each use, with engines off, we hook up dock water and let it flow.

    Have to make sure your exhaust is set up for this as you don’t want the water to sit or backflow from the exhaust elbow. Also, no lift mufflers.

    Mike

    #38380

    Nicholas
    Participant
    Engines: 1200hp Man d28 v12
    Location: Cocoa Beach, Fl
    Country: USA

    Seems like a lot of people pull from a reservoir instead of just attaching to the city/dock water. My understanding is the point of that is to keep from pressurizing the system when the engines are not running, is that correct?

    How much fresh water will a 6CTA suck down in whatever amount of time is appropriate for flushing?

    Edit: also – any thoughts on whether the Tee fitting needs to be mounted vs. just suspended in-line with the hoses?

    #38377

    Kraig Kilger
    Participant
    Location: California

    Correct, you would cut each hose at an appropriate location and tap in. I ran a 3/4″ hose from each tee to a single 3-way ball valve that I mounted on a bulkhead in a location that was easy to reach. I then ran the third hose from the ball valve to a large cooler full of fresh water. Each engine would draw from the cooler when I selected that side from the valve. It does require closing of the seacocks to ensure a flush of solely fresh water and then reopening when finished.

    #38376

    Nicholas
    Participant
    Engines: 1200hp Man d28 v12
    Location: Cocoa Beach, Fl
    Country: USA

    So would i end up with two sections of hose per intake? One section between the sea cock and T-fitting and then another section clamped to the other side of the T-fitting running to the engine?

    Would the resulting T-fitting and flush valve assembly would need to be supported somehow structurally beyond just being clamped to the hoses?

    #38373

    Kraig Kilger
    Participant
    Location: California

    If those hoses are either 1.75″ or 2″, consider using the bronze hose tee fittings that Seaboard sells to tap into the hose after the seacock and before the raw water hose. I used these on my last boat and it worked well.

    #38371

    Nicholas
    Participant
    Engines: 1200hp Man d28 v12
    Location: Cocoa Beach, Fl
    Country: USA

    best way to add freshwater flush to this setup

    Any advice on the best/easiest way to add freshwater flush to the pictured raw water intake setup? Most of the examples I’ve seen are with internal sea strainers. I only have external screens, no sea strainer inside the boat. I thought about adding sea strainers but I don’t have a lot of room given the current geometry (and it’s a lot of money if not needed).

    #38324

    Anonymous
    Inactive

    I am going to introduce myself in the way you have done.
    Future blase

    #37960

    Robert Connolly
    Participant
    Vessel Name: Raging C's
    Engines: QSM11 HP
    Location: Rockaway, NY
    Country: USA

    OK excellent idea. I’ll probably wait until I haul to do that, but it will certainly make things easier. Thanks!

    #37959

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    I was figuring that you would have a fresh water feed fitting on the top of your strainer – either one that is commercially available or have the cover drilled and tapped.

    #37950

    Robert Connolly
    Participant
    Vessel Name: Raging C's
    Engines: QSM11 HP
    Location: Rockaway, NY
    Country: USA

    Thanks for the reply but I’m not sure how that would work? When I open the top of my strainers, if I don’t close the seacock I’ll get a hell of a rush of seawater coming in from the thru-hull. That’s where I am putting the fresh water hose, in the top of the basket strainer housing. Am I missing something?

    #37940

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    It’s even simpler than that. No need to close the raw water seacock. Leave it open and the engine will pull in the fresh water that you are feeding it. Even if what is left in the raw water circuit is almost all fresh you are good. By not closing the seacock you don’t need to worry simultaneously starting the engine and turning on the fresh water so never a risk of running the impeller dry or over pressurizing anything. Do it with the seacock open and then when you pull some zincs you can see what you have sitting in your coolers.

    #37922

    Robert Connolly
    Participant
    Vessel Name: Raging C's
    Engines: QSM11 HP
    Location: Rockaway, NY
    Country: USA

    is it this simple?

    2007 QSM11’s at 670HP. The raw water configuration in my boat makes it somewhat simple to do a Fresh Water wash via the sea strainers. Is it as simple as turning off the raw water intake ballcock, putting a fresh water hose in the sea strainer and running the engine for 2 minutes? Then closing everything up and opening the ballcocks?

    #21676

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    The work involved to do this will pay you back with dividends my times.. Your zincs will last many times longer and the insides of the entire seawater system will never do anything stupid from here on out…………….Good call ..

    Tony

    #21628

    james
    Participant

    My system for Fresh Waterh flush

    What I put in place was pretty easy to do and didn’t cost very much at all. We took the bronze caps off of Groco Strainers and drilled and tapped them for 1/2 inch NPT fittings. To that we added appropriate connections and a 90 degree bend with a ball valve. Attached to the ball valve is 8 feet of hose which is coiled in the bilge.

    Flush process is as follows:

    Pull hose up from bilge connect to a hose attached to dock water. Dock water has been measured to fill a 5 gallon pail in 33 seconds.

    Leave thru hull open, turn on dock water, let things flush reverse out the boat for a few moments.

    Start the engine. Ensure water flow. Go back into engine room and close thru hull to strainer, Engine is now getting pure dockside freshwater feed. Time process by consumption of 1 adult beverage.

    Shut down engine, quickly shut down water from dock.
    Open thru hull valve.

    Lift hose and carry down hill back to the bilge, all water drains out the thru hull. Close freshwater flushing valve.

    Sounds complicated, but it is straightforward process. I am not eating zincs very much, and believe in the benefit. AC’s are coming off when the weather gets a bit cooler, which will be at the 18 month point. I will shoot photo’s of the results at the time. Both AC’s were replaced due to faulty or deferred maintenance prior to my ownership.

    Additional benefit, I ensure that my waterlist mufflers are filled with fresh water, which means my turbo’s should not have salt vapor near them.

    Pictures added in the future next time I get to the boat.

    #20739

    FERNANDO DACOSTA
    Participant
    Vessel Name: FELIZ DREAM
    Engines: Cummins 6cta 8.3 (46086149) & (46086200)
    Location: 13798 NW 20th ST, Pembroke Pines, FL, 33028
    Country: USA

    How to build

    I’d like to build a fresh water flush,
    Do you a have a diagram or pictures on how to make the connections
    How you build that?
    Fernando

Viewing 20 replies - 1 through 20 (of 55 total)

You must be logged in to reply to this topic.