Disappointing Power & Speed

Discussion in 'Sport Boats' started by Tim Sullivan, Jun 29, 2020 at 11:08 PM.

  1. Tim Sullivan

    Tim Sullivan New Member

    2006 Sundeck 200 with 4.3 MPI
    Mercruiser 4.3L MPI Alpha I
    i just bought a 2006 Sundeck 200 with a 4.3 MPI engine. I put a new prop (14.25 and 17 degrees) on it. It has very little power out of the hole and takes a while to plane. It tops out at 4,100 RPMs and only 28 mph. The engine only has 153 hours on it. It is disappointing. Is there anything I can do?
  2. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    Axiom 12 MFD
    Cat 3126 V-Drives
    Not to be rude, but buy a boat with a bigger engine. Seriously.

    I had a 20' with a 4 cylinder thinking it wouldn't burn much gas. WRONG!! I usually ran almost WOT and it burned a ton of gas. Worst boat I've ever owned. Hole shot, top speed all sucked, regardless of prop I installed.

    Another factor is how you load it. Too many people or stuff on board affects performance. That same boat required people to move forward to get on plane with more that 3-4 people on board.

    After that experience, I want the biggest (most h.p./torque) engine combination available. You want to be able to cruise with your normal compliment of people fuel and beer/cooler at a reasonable RPM usually around 3000- 3500 for most gas engines.

    I quickly sold and moved up to a 24 ft with a 5.7 small block. Great boat.
  3. Chip S

    Chip S Active Member

    Jun 17, 2019
    Bordentown, NJ
    1993 Sea Ray 200 Overnighter
    1993 Mercury 150 hp Black Max Outboard
    dlvwill and Chris-380 like this.
  4. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Do a complete tune up
    Change your fuel filter
    Check your compression while you have the plugs out
    Check your fuel pressure at WOT
    dlvwill and Chris-380 like this.
  5. Tim Sullivan

    Tim Sullivan New Member

    2006 Sundeck 200 with 4.3 MPI
    Mercruiser 4.3L MPI Alpha I
    i did change the fuel filter and have put two tanks of new gas in it. Maybe I will have get a tune up.
  6. Arminius

    Arminius Member

    Oct 30, 2019
    Bowrider 200 Select, 2003
    5.0L MPI, 260 hp w/Alpha 1 Drive
    Better take it to a dealer/marina with the electronic equipment to diagnose the engine. Ask them to take it out for a test cruise. Your first problem is finding a reliable mechanic who knows what he is doing and wants to keep your business in the long term. He is likely to be busy now. A family owned marina would be good. You are going to have dealer only maintenance in the future. I analyzed my 2003 5.0 MPI and realized the computer was not automotive and required a marine Rinda $500+ code reader.
  7. paulswagelock

    paulswagelock Well-Known Member

    Oct 25, 2010
    2018 SDX 270 OB 300 Verado
    Verado 300
    That is plenty of motor for that boat. Get the engine checked- not running to its fullest potential.
    Chris-380 likes this.
  8. Tim Sullivan

    Tim Sullivan New Member

    2006 Sundeck 200 with 4.3 MPI
    Mercruiser 4.3L MPI Alpha I
    Thanks. I am in CT and Marinas are three weeks out.

    I do have vessel view. Is there a reading in there that might might give me clue?
  9. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    Before you go down the mechanical road - which could certainly explain it - anything from a plug wire not secured to, well, just about anything...

    Is the boat bottom and running gear perfectly clean?

    Are you trimming the drive properly?

    Did you check speed with GPS or just the speedo?

    When you changed the fuel filter, did you dump the gas into a glass jar to check quality? If the gas was old, it may have gummed/fouled the injectors.
  10. blaster

    blaster Well-Known Member SILVER Sponsor

    May 23, 2011
    potomac river
    2010 sea ray 205 sport
    F-250 CCLB 6.2 4x4 3.73 rear.
    Mercruiser 4.3 mpi alpha 1.62
    That boat should be running mid 40MPH range.

    Definitely something amiss.

    Boats often present with a shine outside but mechanical maintenance has been neglected.

    it’s almost always worth the time and money to have a mechanical survey before purchasing.
    ecrouch01 likes this.
  11. ENstig8or

    ENstig8or Active Member GOLD Sponsor

    Jun 4, 2013
    New Jersey
    2003 Sea Ray 450 Express Bridge.....

    2016 Sea Ray 21 SPX BR
    Cummins 480CE (450)
    Mercruiser 4.3L (21 SPX)
    That engine should turn around 4700-4800 RPM's and run at least 40 MPH with the correct prop. As others have said above, there are other issues preventing top performance.

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