Registered users don't see ads

Can I flood my engine trying to start it?

Discussion in 'Ask All Sailors' started by markwbird, Feb 1, 2019. Add this thread to a FAQ

  1. markwbird

    markwbird

    Joined Nov 26, 2012
    952 posts, 214 likes
    Hunter 34
    US Berkeley
    So, here’s another dumb question: why does the raw water that goes through the heat exchanger get pumped into the exhaust system? Why not just send it overboard separately? Is it just to cool the exhaust?
     


  2. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    2,233 posts, 942 likes
    Catalina 36 MK1
    US Everett, WA
    Yes, I have seen an Alden iirc, that had concentric copper exhaust, water in outside annulus, exhaust on the inside. Sounds like maintenance nightmare but new owner worried cut a section open and good as new.
     


  3. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    2,233 posts, 942 likes
    Catalina 36 MK1
    US Everett, WA
    James, do you think that little anti-siphon valve would keep up with the water pump??? It is there to prevent siphoning not back flow.

    Edit: on further reflection that valve is only open in vacuum conditions, so it would be closed 100% in this situation
     


  4. Don S/V ILLusion

    Don S/V ILLusion

    Joined Sep 25, 2008
    5,255 posts, 421 likes
    Alden 50
    US Sarasota, Florida
    Recipe for disaster. Assuming it never fails, gets clogged (and fails) or disintegrates from the heat (another fail cause).
     


  5. TomY

    TomY Alden Forum Moderator

    Joined Jun 22, 2004
    1,557 posts, 1,318 likes
    Alden 38' Challenger yawl
    US Rockport Harbor
    That's right, and silence the exhaust. The raw water cools everything starting at the injection elbow and everything downstream. An inch or 3 settles in the base of your muffler as exhaust pressure forces plugs of water out of the muffler(which almost eliminates the exhaust sound), and through the rubber exhaust hose.
     


  6. JamesG161

    JamesG161

    Joined Feb 14, 2014
    3,466 posts, 1,221 likes
    Hunter 430
    US Waveland, MS
    Reflect on two hydraulic situations...
    1) Static
    2) Dynamic

    The high point vent can open or not closed tightly in both.

    This thread has mingled both condition 1 and 2.
    Jim...
     


  7. TomY

    TomY Alden Forum Moderator

    Joined Jun 22, 2004
    1,557 posts, 1,318 likes
    Alden 38' Challenger yawl
    US Rockport Harbor
    That was me, Leslie. In fact, they used to build wet exhaust systems that didn't have this exact problem.

    This 1961 exhaust was built of two copper pipes, one inside the other. It had to fabricated to the boat, bent, and the ends in the outer pipe brazed so as to form a separate water chamber, around the hot innder exhaust pipe.

    The the fabricator added taps at each end forming an outer chamber isolated from the inner exhaust pipe.

    The end just aft of the exhaust manifold connected to a hose off the raw water side of the exchanger. This pumped raw water around the inner pipe, cooling it, and then the raw water exited out of the double pipe just before the high loop under the aft deck.

    Out that exit, the raw water - via a smaller copper pipe, entered a cast iron muffler where it was mixed - safely below the high loop, and exited the stern.

    No way for raw water to enter the inner exhaust and flood the engine.

    What worried me is that there is no way of knowing the condition of the inner pipe. When it failed, raw water pumped in before the exhaust pressure built, would immedietley flow into the exhaust manifold and engine.

    Sadly, it had a century of use left. But how would you know? Cost alone makes this system obsolete.

    FullSizeRender 23.jpg

    These are smart questions Mark is asking. Many people have no idea what's going on it their wet exhaust system.
     


  8. dlochner

    dlochner

    Joined Jan 11, 2014
    3,142 posts, 1,420 likes
    Sabre 362
    113 US Fair Haven, NY
    Yes. The water cools the exhaust gases which are around 1K*. Cooling the exhaust allows the use of synthetic/rubber hoses which makes it easier to run the exhaust out of the boat. The water lift muffler helps to dampen the sound of the motor, which makes motoring for longer distances more tolerable.
     


    TomY likes this.
  9. AlexB

    AlexB

    Joined Aug 9, 2016
    26 posts, 8 likes
    C&C 36
    US Great Kills harbor.
    sorry for spelling. first of all you should find out, if you are in danger. do you have raiser or not, is your wet ehsost water inlet higher, then muffler and ehsost outlet. if you are not sure, test is simple: disconect exhost hose from engine elbow or raiser and try to fill it with water(hose or bukket). if it fills, you in danger, if drains out-nothing to worry about.
    if you are in danger, I would put a bypass hose with valve from before and after pump to prevent running dry and damage in any convinient for you place or just put 3 ways valve befor exhost, so water goes to bilge. My engine exhost is much higher, than mufflerand i can crank it all day long, but nothing happens.
     


    Last edited: Feb 4, 2019
  10. dziedzicmj

    dziedzicmj

    Joined Aug 13, 2012
    493 posts, 92 likes
    Catalina 270
    CA Ottawa
    Some people install a seacock valve on the exhaust throughhull, especially, if they use the boat for long off-shore passages. Of course, the trick is to remember to open it, when you want to use the engine.
     


  11. JamesG161

    JamesG161

    Joined Feb 14, 2014
    3,466 posts, 1,221 likes
    Hunter 430
    US Waveland, MS
    Well that would be like the...
    "Banana in the tail pipe" trick.:laugh:

    Check out this link my post#28 for my boats muffler system.
    https://forums.sailboatowners.com/index.php?threads/water-in-engine.175063/page-2

    Note there is always seal water in the muffler. In the Elevation view, imagine the bow going down in say 4 foot seas.
    Water will slosh into the non running engine open exhaust valve.:(

    Most water quench exhaust systems were designed for calm seas.
    Jim...
     


  12. dziedzicmj

    dziedzicmj

    Joined Aug 13, 2012
    493 posts, 92 likes
    Catalina 270
    CA Ottawa
    True. From what I read, on long passages, people were having problems with following seas pushing water into the muffler. So the seacock was not to prevent the remnants of the water in the muffler from sloshing back into the engine, but to prevent more sea water entering the muffler from behind.

    In order to prevent your problem (sloshing water from the muffler entering the engine), you might need to drain the muffler for a long passage. A major PITA, I imagine.
     


  13. JamesG161

    JamesG161

    Joined Feb 14, 2014
    3,466 posts, 1,221 likes
    Hunter 430
    US Waveland, MS
    I suggested that my forum post, but no one responded.

    Most of my sailing, in high sea states, thus I like to start my engine just in case I need to maneuver quickly.
    Others may want to consider a muffler drain.
    Jim...
     


  14. Charles Erwin

    Charles Erwin

    Joined Jan 30, 2012
    1,020 posts, 144 likes
    Nor'Sea 27 - "Kiwanda"
    US Portland/Anacortes
    There is a way to avoid this.

    Good motor installation includes a vented loop - this loop is in the hose that spills seawater into the mixing elbow exhaust and overboard. The loop rises above the waterline to the vent. This vent prevents siphoning of sea water when the motor is off (siphoning is another way to put sea water in the motor.)

    Put a tee in the uphill side of this loop and run a tube from that tee to a small through hull at the rail - above the water line but slightly below the level of the top of the loop. Now when cranking the cooling sea water goes overboard via this new tee, tube and through hull. Very little of it goes into the mixing elbow and the water lock because the sea water volume at cranking speed is pretty low. The waterlock section does not backfill and motor does not hydrolock. When the motor is running the volume increases and the sea water also spills into the mixing elbow and overboard thus cooling the water lock section. You need to size the new tube a little smaller or put a simple valve at the through hull if you want. You don't even need the vented loop because this new overboard prevents siphoning too.

    Good reading concerning exhaust design at Seaboard Marine. https://www.sbmar.com/articles/designing-a-marine-exhaust-system/ . Tony discusses the fix I describe here but he gives you pictures and diagrams too.

    Charles
     


    Last edited: Feb 5, 2019
    jssailem and markwbird like this.
  15. Davidasailor26

    Davidasailor26

    Joined May 17, 2004
    1,508 posts, 350 likes
    Beneteau Oceanis 37 LE
    US Havre de Grace
    A seacock in the exhaust might still help prevent the water from sloshing backwards from the muffler as well. If the exhaust line is closed then no air can enter the muffler from the back, so a column of water won't be able to go towards the engine without generating suction in the muffler. That suction would stop the slosh, unless it wasn't a full column in the line between the elbow and the muffler.

    Having said that, I'd be really worried about forgetting to open a seacock like that. We know people sometimes forget the intake seacock, and a burnt impeller is nothing compared to the mess that a stopped exhaust may cause.
     


  16. JoeMerchant

    JoeMerchant

    Joined Feb 5, 2019
    6 posts, 3 likes
    Pearson 303
    US Jacksonville, FL
    At the risk of stating the obvious: engine cranking time can be reduced by opening the throttle...

    I was blessed with a very easy-starting Yanmar 2GMF, usually one bump on the starter button and it just catches and runs with the throttle set to idle position, even when stone cold and not run for a week. I have also been "trained" by electronic fuel injection automobiles for the past couple of decades to forget about "pumping the accelerator" or even opening the throttle while starting.

    So, when we had a guest on board (sister in-law) and the engine didn't catch on the first, second, third... tenth attempt bumping the throttle for 2-20 seconds, it just didn't occur to me to try opening the throttle. For my engine just a mid-range opening seems to be all it needs to catch when it doesn't want to start at idle throttle. After that, it went back to easy starting until our last trip - that time I remembered to try the throttle opening after about 5 attempts at idle, and caught first time.

    Yes, it's obvious bordering on common sense, but just incase another diesel newbie wanders into this thread...
     


    dziedzicmj likes this.
  17. Stu Jackson

    Stu Jackson

    Joined Feb 26, 2004
    20,258 posts, 780 likes
    Catalina 34
    224 CA Maple Bay, BC, Canada


    Last edited: Feb 7, 2019
  18. Gunni

    Gunni

    Joined Mar 16, 2010
    5,765 posts, 1,397 likes
    Beneteau 411 Oceanis
    US Annapolis
    The total volume of a wet exhaust system (muffler/hose), and the rise to the intake manifold should be more than adequate to handle coolant water, for any reasonable pitch angle of the boat. Offshore we have a couple of nerf footballs which fit the thru-hull exhaust port nicely. That is a $2 fix.
     


    dziedzicmj likes this.
  19. TomY

    TomY Alden Forum Moderator

    Joined Jun 22, 2004
    1,557 posts, 1,318 likes
    Alden 38' Challenger yawl
    US Rockport Harbor
    When I designed my system, for that reason - volume - I went with a larger capacity water-lift muffler. As a typical old CCA design, the 'resting' volume of raw water is at a max. The extra volume keeps all the flow back in the bottom of the muffler.

    Then to not worry about back flooding(and adding more water volume), I resisted the temptation to put my exhaust outlet in the counter where it wouldn't show.

    I stuck with the 1959 design drawing thinking Alden design had a long track record of engine floodings, and picked this location.

    Even with the high loop before the exit for added protection (my new hose high-loops all the way up the aft deck), I see a potential for a plug of water to get pushed up, especially if the outlet were re-located to the counter.

    In a seaway, running downwind (something we do for hours and hours), if the outlet stays under for several waves, a plug may push - and over the high loop,...and you have a siphon.


    Exhaust detail 2.jpg

    So I kept the high outlet location, raised the raw water vented loop to just beneath the bridge deck and so far so good.

    Even this high location still goes under for short periods. Any sort of seacock wouldn't work for me. It wouldn't be easy to get to, too much potential to not use it - or use it and forget it.
    TT applies stars 2017 (1 of 1).jpg
     


  20. Gunni

    Gunni

    Joined Mar 16, 2010
    5,765 posts, 1,397 likes
    Beneteau 411 Oceanis
    US Annapolis


    dziedzicmj likes this.

Sunbrella lifesling covers
Any color, fits over existing bag to match your existing canvas.
Stainless documentation placard
Who said a documentation placard cant be beautiful? Brushed stainless with laser-fused numerals.
Sail Trim Chart and Guide
When it comes to sailing, as basic as salt and pepper and just as indispensable!
Too hot? INSTANT BIMINI ESTIMATES
Low prices, custom fit, no-wait estimates