Sea Water pressures

Discussion in 'General Discussion' started by SeaRenity, Jun 22, 2019.

  1. SeaRenity

    SeaRenity Member

    170
    Mar 31, 2008
    chesapeake bay / Back river
    320 Sundancer 2005
    350 Mag hor.
    just changed my raw water pump and it seems my smartcraft water pressure is low and engine running a little hotter.

    I have a 350 mag horizon
    starboard 4.5 @1500 RPM and 18.2 at 3600
    port ( new) 4.4 @ 1500 and 12.3 at 3600

    does anyone know if this is acceptable and in range?

    thanks
    Rich
     
  2. Espos4

    Espos4 Well-Known Member

    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    Those are good numbers.

    What are your engine temperatures at idle and cruising speed?
     
  3. SeaRenity

    SeaRenity Member

    170
    Mar 31, 2008
    chesapeake bay / Back river
    320 Sundancer 2005
    350 Mag hor.
    Engine temps were stable for both engines at 163-165.
    Now port rises to 168-170
    Does anyone have smart craft water pressures at cruise speed???????
    Rich
     
  4. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    I would probably start with swapping the water pressure senders and make sure that the port engine is actually flowing less water.

    If the numbers remain the same then you probably have a restriction in the heat exchanger. Why did you replace your raw water pump?
     
    Leardriver likes this.
  5. Espos4

    Espos4 Well-Known Member

    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    Cruising in the 3,200-3,500 rpm range I see anywhere from 9-12 psi.

    It’s been that way for the last 3 years. In that time I’ve replaced manifolds and risers and also a new raw water pump impeller this year.

    Same range before and after.
     
  6. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Changed the pump or impeller ? New impeller in one of those easily scored brass pump will do that. A restriction downstream of the pump would make you pressure read higher not lower.
     
  7. Craig

    Craig Well-Known Member GOLD Sponsor

    534
    Feb 8, 2007
    Maryland
    2006 320 Sundancer
    twin 350 Horizon V drives
    Mine stay at 13 to 16.
    20190623_101815.jpg
     
  8. Korkie

    Korkie Active Member SILVER Sponsor

    520
    Feb 2, 2016
    Leonardtown, MD Potomac River / Chesapeake Bay
    340 Sundancer 2006, Garmin 7612, xHD Radome
    Merc 496 Mags
    Bravo III Drives
    +1 on scoflaw - - Restriction downstream increases pressure. Low pressure means pump is starving for water. Check your strainer baskets n make sure clean and sea cock is all the way open. Is/was your pump housing scored bad? This can also cause lower pressure as water leaks by the scores. The problem is before or at the pump. Could also have an obstruction at the intake under the boat (barnacles, paint build up, piece of whatever partially obstructing). The numbers you posted above are good at 1500, but the lower pressure on the port side and with it running a wee hotter indicates not enough volume input (water) to the pump at the higher rpms to get you the adequate pressure to give you the proper flow to cool the engine. Your 3600 rpm pressures should both be in the high teens.
     
  9. SeaRenity

    SeaRenity Member

    170
    Mar 31, 2008
    chesapeake bay / Back river
    320 Sundancer 2005
    350 Mag hor.
    Changed pump due to seal failure. Mechanic insisted he installed a new pump, I believe he did but I might have a Sierra not mercruiser.
    Thanks for everyone's response
    Rich
     
  10. Leardriver

    Leardriver Member

    181
    May 24, 2016
    Denver, CO
    2004 270 Sundeck 8.1 Bravo III
    5.0, 5.7, 6.2 8.1 Bravo III over the years
    Bravo or Alpha drive? The Bravo's get Bravoitis and the intake tube gets squeezed shut.
     
  11. Korkie

    Korkie Active Member SILVER Sponsor

    520
    Feb 2, 2016
    Leonardtown, MD Potomac River / Chesapeake Bay
    340 Sundancer 2006, Garmin 7612, xHD Radome
    Merc 496 Mags
    Bravo III Drives
    SeaRenity - If you have Bravo 3 drives as asked above, your problem is most likely Bravoitis. Unless you have had the new tube kits installed in your drives. It is very easy to check. let me know if you indeed have the drives and I will explain how to check it and the options how to fix it. Just went through same thing last season.
     
  12. dieselsmoke

    dieselsmoke Member

    88
    Aug 21, 2016
    nj
    2004 Select 220
    5.0mpi bravo
    If you could kindly post the "how to tell" I would appreciate it. I have a Bravo 3, Thankfully no problems on my 2004 5.0 at this point but since Bravoitis is a real thing Id like to know if the previous owner may have already installed new tubes or if I should put it on the to do list after this season. Thanks
     
  13. Korkie

    Korkie Active Member SILVER Sponsor

    520
    Feb 2, 2016
    Leonardtown, MD Potomac River / Chesapeake Bay
    340 Sundancer 2006, Garmin 7612, xHD Radome
    Merc 496 Mags
    Bravo III Drives
    If you follow your input hose from your sea water pump to the transom, you will see where it goes through. Disconnect it at the transom and if you have Bravoitis it will be obvious.
     
  14. Korkie

    Korkie Active Member SILVER Sponsor

    520
    Feb 2, 2016
    Leonardtown, MD Potomac River / Chesapeake Bay
    340 Sundancer 2006, Garmin 7612, xHD Radome
    Merc 496 Mags
    Bravo III Drives
    Here is a pic of what Bravoitis looks like. 18318.jpeg
     
  15. dieselsmoke

    dieselsmoke Member

    88
    Aug 21, 2016
    nj
    2004 Select 220
    5.0mpi bravo
    Ok Thanks, That photo is looking down the hose that passes thru the transom and out to the drive correct?
     
  16. Korkie

    Korkie Active Member SILVER Sponsor

    520
    Feb 2, 2016
    Leonardtown, MD Potomac River / Chesapeake Bay
    340 Sundancer 2006, Garmin 7612, xHD Radome
    Merc 496 Mags
    Bravo III Drives
    Yes.
     
  17. b_arrington

    b_arrington Active Member GOLD Sponsor

    934
    Feb 21, 2007
    Setauket, NY
    2018 Back Cove 34
    Cummins QSB 6.7 480
    If you have a through-hull water intake Bravoitis isn’t an issue. Check to see if you have one before getting too concerned.
     
  18. Korkie

    Korkie Active Member SILVER Sponsor

    520
    Feb 2, 2016
    Leonardtown, MD Potomac River / Chesapeake Bay
    340 Sundancer 2006, Garmin 7612, xHD Radome
    Merc 496 Mags
    Bravo III Drives
     
  19. Korkie

    Korkie Active Member SILVER Sponsor

    520
    Feb 2, 2016
    Leonardtown, MD Potomac River / Chesapeake Bay
    340 Sundancer 2006, Garmin 7612, xHD Radome
    Merc 496 Mags
    Bravo III Drives
    Most Stern drives do not have through hull unless added. If you do not have a through hull, adding one is the best fix in my opinion. That is what I did on several recommendations.
     
  20. b_arrington

    b_arrington Active Member GOLD Sponsor

    934
    Feb 21, 2007
    Setauket, NY
    2018 Back Cove 34
    Cummins QSB 6.7 480
    Agreed on the adding part. Sea Ray installed a through hull intake at the factory for my boat. It’s worth checking.
     

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