Over propped??

Discussion in 'Classic Sea Rays' started by zeddy, Jan 13, 2019.

  1. zeddy

    zeddy New Member

    19
    Aug 7, 2018
    1985 Searay 210 Seville Mid Cabin
    Mercruiser 5.0LX/ Alpha One
    Last weekend, a few of us took our seville mid cabin out fishing. 5 adults. The boat would take forever to plain. With her at full throttle, she would run around 3k rpm at about 10mph. Absolutely would not plain even with the trim tabs down. When I had a one person move towards the cabin, she would finally plain and rpm and speed pick up to around 3500 rpm at about 27-30mph. When I’d let off the throttle to around 3000-3200 rpm she would continue to cruise at around 20mph.



    If I’d lower the rpm anymore, 2800-3000rpm she will slow down and drag to 10-15 mph.

    The motor is mercruiser 5.0.

    Am I just heavy? Or does it sound I’m over propped?? Is cruising rpm noted above too much? I don’t want to hurt anything.
     
  2. electricaldoctor

    electricaldoctor Well-Known Member TECHNICAL Contributor PLATINUM Sponsor

    May 14, 2008
    Thousand Islands, Rockport, Ontario.
    1988 390 EC
    454 Mercruiser Gassers
    What are your current prop specs? Is it the same as the original specifications?
     
  3. zeddy

    zeddy New Member

    19
    Aug 7, 2018
    1985 Searay 210 Seville Mid Cabin
    Mercruiser 5.0LX/ Alpha One
    I don’t know what the specs are. It’s usually stamped on the prop right?
     
  4. electricaldoctor

    electricaldoctor Well-Known Member TECHNICAL Contributor PLATINUM Sponsor

    May 14, 2008
    Thousand Islands, Rockport, Ontario.
    1988 390 EC
    454 Mercruiser Gassers
    correct.
     
  5. Strecker25

    Strecker25 Well-Known Member

    Nov 20, 2014
    Rochester, NY
    1998 290 Sundancer
    Twin 5.7EFI/Alphas, Kohler 4kw
    Gotta load her up to your typical cruising weight, get a nice calm day, and run up to WOT to see what the motor will turn. Double check your specs, but the SBC’s are usually 4400-4800. If you’re in that range, you’re good. If it’s low, make sure the bottom is clean first, then talk to a prop shop to pick up the extra revs through reworking your prop or trying different ones.
     
    techmitch likes this.
  6. hottoddie

    hottoddie Well-Known Member

    Jan 11, 2012
    Boston/Cape Cod
    1986 Sea Ray 390 EC
    Garmin 4212 Chartplotter
    Garmin 24 HD Radar
    Garmin 546s Plotter
    454 Crusaders
    That's a lot of weight in a 21ft IO boat with 5.0 liter alpha1. Five 150lb adults are a lot different than 5 250lb adults. With 2 adults and full fuel do you reach 4500-4600 rpm? If not then you may be over propped. That boat would act totally different with a 5.7 and bravo1 drive. You may be expecting too much from the 5.0 alpha.
     
  7. zeddy

    zeddy New Member

    19
    Aug 7, 2018
    1985 Searay 210 Seville Mid Cabin
    Mercruiser 5.0LX/ Alpha One
    Im thinking she was weighed down. The 5 adults are around 200lbs each, full tank of gas and water, gear, bait tank.

    I’ve had her out with only my dad and son but never had the opportunity to open her up. I’ll try to the pitch on the prop later today.

    I know these boats came from the factory with 6 cyclinder motors. If the 5.0 is struggles, I couldn’t imagine the 6 cylinder.
     
  8. Espos4

    Espos4 Active Member

    643
    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    I had a 4.3 MPI 220 HP in a 20’ Crownline 206LS.

    With 5-6 people aboard, it wouldn’t plane unless 1 or 2 were in the bow seats.

    It ran well with 3-4 people in calmer waters but was a chore in choppy water and constantly losing plane.
     
  9. sbw1

    sbw1 Well-Known Member

    Oct 10, 2006
    West Michigan
    This is listed in my signature
    This is listed in my signature
    tiara in the snow 01.JPG You need to be able to reach the spec'd WOT for your engine. Go to a Merc Web site, look it up and write down that number. Then, as someone suggested earlier, see what the boat will achieve with full fuel, a "normal amount" of gear, and a proper state of tune. The boat should achieve that WOT. If it does not, you are overloading the engine and need to reprop to achieve the number.
     
  10. zeddy

    zeddy New Member

    19
    Aug 7, 2018
    1985 Searay 210 Seville Mid Cabin
    Mercruiser 5.0LX/ Alpha One
    All the prop says is 4893272. And AA15P
     
  11. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Doesn't get much lower than a 15. You probably have other issues

    Bent prop
    growth on hull
    Motor getting tired
    Overloaded cargo
     
  12. Thornton69

    Thornton69 Active Member

    314
    Sep 15, 2014
    Northern BC
    1980 245 SDC
    1984 18' Valco sled
    5.7 260 Merc/ Bravo 2
    Evanrude 115/80 jet
    Sounds like your engine is not making full power.
    When was your fuel filter last changed?
    May also want to confirm throttle linkage is fully advancing.
     

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