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  1. #1

    Default Mercruiser 5.0L - Advice required regarding flushing

    Hi all,
    I am new to this forum and considering getting my first boat which is a 2009 Sea-Ray 205 with V8 Mercruiser 5.0.
    I want to keep the boat in a saltwater marina and am concerned with the problems which may occur if I cannot flush the engine. The thing is I cannot find exact information regarding if there is a possibility to flush these engines in the water (I have heard of fresh water flush kits you can get?) Do these work? I see many other boats which are birthed in the marina and I assume they don't all have problems.
    Another issue is that I believe the 5.0L is raw water cooled rather than having it's own seperate cooling system like the 4.2 so hence should be flushed every time?
    Any advice / help greatly appreciated!
    Thanks
    Daniel

  2. #2
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,308

    Default Re: Mercruiser 5.0L - Advice required regarding flushing

    Saltwater environment is extremely corrosive. You can convert the engine to partial FWC (engine block) or total FWC (engine and manifolds) for under $1,500. Keep an eye on the sacrificial annodes on the OD. Make sure the cathodic system is working. Merc. makes an engine/OD exterior protective spray to reduce corrosion.

  3. #3

    Default Re: Mercruiser 5.0L - Advice required regarding flushing

    Hi guyjg,

    Thanks for the reply, this isn't really an expense I was looking to have right from the start! Maybe I will consider getting a boat with a closed loop cooling system. The thing is I see loads of boats in the marina with raw water engines and assumingly not many problems!

    Would appreciate anyones feedback on the fresh water flush kits and if they are any use?

    Thanks

    Daniel

  4. #4
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    7,221

    Default Re: Mercruiser 5.0L - Advice required regarding flushing

    Daniel, yes..... the closed cooling system would be much better for you, IMO.

    You can use the flushing systems...... Salt-a-Way is one them.
    These introduce a neutralizing chemical into the cooling water side.
    However, there is a catch with the A drive, in that the sea water pump is in the lower out drive unit.
    These kits are more effective, IMO, with an engine mounted sea water pump.

    NOTE: Use extreme caution if any of you consider using these kits to winterize with.
    This is topic that has been discussed here in the past. More later if interested.
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  5. #5
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,308

    Default Re: Mercruiser 5.0L - Advice required regarding flushing

    .. Sea-Ray 205 with V8 Mercruiser 5.0...
    The MPI 4.3L V-6 is a better overall engine compared to the 5.0L V-8. A much better HP:weight ratio for a 20' boat. If you want a V-8 get a 5.7 MPI. Same weight as a 5.0L but more HP. IMO it's better to lumber along w/a 5.7 than to push a 5.0L.

  6. #6
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    3,174

    Default Re: Mercruiser 5.0L - Advice required regarding flushing

    Save your money. If you get a raw water cooled boat and keep it in salt water it will last 20 plus years. Do you plan on keeping this boat that long? Saltwater does most of it's damage to trailered boats.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Let the insanity begin.

  7. #7
    Join Date
    Aug 2011
    Location
    Portsmouth, Va.
    Posts
    66

    Default Re: Mercruiser 5.0L - Advice required regarding flushing

    Yes you can flush engine in water while docked. I had a 32' bayliner that stayed in water unless taken out by marina. You just lift out drive to trailer put muffs on and turn-on water, lower out drive as little as possible to put outlive in safe operating range and start motor. I have even used salt away in water.

  8. #8

    Default Re: Mercruiser 5.0L - Advice required regarding flushing

    Quote Originally Posted by Docksidemarineservices View Post
    Save your money. If you get a raw water cooled boat and keep it in salt water it will last 20 plus years. Do you plan on keeping this boat that long? Saltwater does most of it's damage to trailered boats.
    Hi Chris,

    I find this interesting - I don't plan on keeping the boat for more than 2 years at this stage, I am however interested in understanding how saltwater damages trailered boats more than those kept in the water?

    Thanks in advance!

  9. #9
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    3,174

    Default Re: Mercruiser 5.0L - Advice required regarding flushing

    Quote Originally Posted by actros View Post
    Hi Chris,

    I find this interesting - I don't plan on keeping the boat for more than 2 years at this stage, I am however interested in understanding how saltwater damages trailered boats more than those kept in the water?

    Thanks in advance!
    As long as the salt from the water stays in solution it will take 20-25 years to damage your engine to the point of needing replacement.

    I should have been more clear on my post. Rack stored boats have more build up and corrosion on them then ones left in the water. Most rack stored boats never get flushed between uses. Hence the H2O evaporates and leaves behind all the salt and minerals in the sea water.

    When I was a kid there was a mechanic we used in Virgina. He had a tank filled with sea water with a couple of outboard engines soaking in it. I asked why, He said "They came off a boat that has sunk" and left them in a tank of water because he did not have time to get to them. He said "As long as they stay wet the salt will not do any damage"

    So unless you are rack storing your boat and not planning on flushing it, or you are planning to keep it for many years, Save your money on the FWC kit.

    Also, most boats kept in the water receive there corrosion damage from electrolysis caused by older less maintained boats around them.
    Last edited by Docksidemarineservices; 09-25-2011 at 09:51 AM.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Let the insanity begin.

  10. #10

    Default Re: Mercruiser 5.0L - Advice required regarding flushing

    Quote Originally Posted by Docksidemarineservices View Post
    As long as the salt from the water stays in solution it will take 20-25 years to damage your engine to the point of needing replacement. I should have been more clear on my post. Rack stored boats have more build up and corrosion on them then ones left in the water. Most rack stored boats never get flushed between uses. Hence the H2O evaporates and leaves behind all the salt and minerals in the sea water.When I was a kid there was a mechanic we used in Virgina. He had a tank filled with sea water with a couple of outboard engines soaking in it. I asked why, He said "They came off a boat that has sunk" and left them in a tank of water because he did not have time to get to them. He said "As long as they stay wet the salt will not do any damage" Thanks for the reply - hopefully I will soon be a happy owner of my first boat AND not worry about keeping it in the water!So unless you are rack storing your boat and not planning on flushing it, or you are planning to keep it for many years, Save your money on the FWC kit.Also, most boats kept in the water receive there corrosion damage from electrolysis caused by older less maintained boats around them.
    Many thanks for the reply! Hopefully I will soon be the owner of my first boat and be able to keep it in the water!

  11. #11
    Join Date
    Aug 2011
    Location
    Foss Landing & Marina Tacoma,Wa
    Posts
    50

    Default Re: Mercruiser 5.0L - Advice required regarding flushing

    From doing a bit of research and being around salt water boats since the 60's in my opinion the damage done from salt is due mainly from the castings of the blocks,heads and manifolds a sea water cooled engine is recommended to run at 140-160 degrees closed loop systems run at 170 while at running temp the castings expand because of how porous they are the minerals get trapped in there as the engine cools down. If you flush the engine after it has cooled down not bringing it up to running temp those minerals stay trapped which starts the corrosin problems. I keep our boat in indoor rack storage every time the boat is stored it is flushed and brought up to 170 degrees boat is also scrubbed down and power washed. I prefer a closed system all you need to worry about is manifold and risers being maintained. Keep an eye on the mercathode system in a marina most OD problems come from other boats or power leakage. Just my opinion not an expert.

  12. #12
    Join Date
    Aug 2007
    Location
    , Florida, USA
    Posts
    51

    Default Re: Mercruiser 5.0L - Advice required regarding flushing

    Just an observation. Most of the boats that are run intermittenly and hung up to dry seam to have more problems with corrosion and everything elsse. The fishing boats in South Florida that go out all the time.....go out all the time! Use it or lose it.
    I believe that exposing the cast iron parts to air with hungry oxygen is asking for ttrouble. I'm not against flushing and using Salt away. At least you will get rid of one of the culprits.

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