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  1. #1
    Join Date
    Dec 2008
    Location
    Sarnia, Ontario, Canada
    Boat
    Sea Ray
    Details
    340 Amberjack
    Engine(s)
    twin 8.1S 370 Hp + 4.5 Westerbeke Genset
    Posts
    1,468

    Unhappy What's wrong with my 8.1 Horizon Engine?

    Splashed the boat today. I was looking forward to having both engines operate at the same WOT now that the props have been redone, but...

    The stb engine still lags behind the port engine (like last year). Both are the same until around 2000 rpm, then to keep the engines sync'd more throttle must be applied to stb. My normal cruise speed is 3500 rpm and at that speed, both engines seem to operate well enough. It's just that the stb engine must have about 10-15% more throttle to maintain sync. It was also using more fuel last year than the port engine.

    It gets more evident past this point that there is an obvious issue. If I try to increase both to 4000 rpm, the stb throttles must be to the wall, while the port throttles still have plenty of room. (I didn't run this way long for fear of causing damage to something ) After reducing speed with both engines to 3500 rpm, I tried increasing the speed first on the stb without altering the port. I could hear and feel a shutter as I applied throttle. The same test was done with the port engine, it simply gunned ahead and the boat began to be steered by the increased thrust on the port prop.

    Before docking I tested it off plane, at idle with both engines in gear. Spinning the boat port or stb by using each engine allowed me to hear and feel more distinctly that the stb engine is not smooth running and powerful like the port engine. Once throttle is applied, the shake and paa-paa-paa sound is evident. Other than this, the engine starts well, runs well (at lower rpms), and doesn't use oil.

    I've got my plan of action to try and diagnose, but wanted to get those smarter/more experienced (or both) to provide some advice first.

    FYI - I purchased the boat late summer 2008 and have not really taken it on any long trips. I don't know what has or has not been replaced on the boat other than the things I've done since ownership. The issue was noticed last year, but I decided to have the props balanced first to rule out that as an issue (which was a good thing since the props were badly pitted from electrolysis and they were out of balance).

    Please - Bring on the wisdom.
    Posted by Jim of "Island Rhythm"
    2001 Sea Ray 340 Amberjack
    LOA 38', approx 18,000 lbs & 13.5' Beam
    Straight Shaft Drives


  2. #2
    Join Date
    Oct 2007
    Location
    Washington Park Marina, Michigan City
    Boat
    Sea Ray
    Details
    '07 340 DA, E80, Vessel View, Soft Top '12 Boston Whaler 15 Montauk
    Engine(s)
    8.1 Mercruiser V-Drives, Mercury 60 HP Bigfoot
    Posts
    11,514

    Re: What's wrong with my 8.1 Horizon Engine?

    If the plugs and wires haven't been changed in a while, that would be a good place to start.
    Scott of the most excellent Sea Ray "Destiny".
    "There's only two things that excite a man, expensive toys and real expensive toys."




    Quando omni flunkus moritati
    Previous boats: '03 320 DA, '01 280 DA, '95 270 DA, '81 260 DA, '87 230 WE, '66 Boston whaler 13 sport, '75 BW 13 Sport, '87 BW 15 Supersport, '09 BW 15 Supersport and a couple of dinghies.

  3. #3
    Join Date
    Apr 2009
    Location
    long island
    Boat
    sea ray
    Details
    370da
    Engine(s)
    7.4's
    Posts
    224

    Re: What's wrong with my 8.1 Horizon Engine?

    I would start with the basics. Compression test first. Inspect the spark plugs. They should all be clean and show an even burn. If all is correct start looking at ignition and fuel supply. ? could you have water in one tank ? Also check fuel pump pressure. Keep us informed as to what you find please

    1998 370da 7.4 mpi
    Long Island N.Y.

  4. #4
    Join Date
    Nov 2006
    Location
    Panama City, Fl
    Boat
    Sea Ray
    Details
    2008 44 Sedan Bridge
    Engine(s)
    Cummins QSC-500's Straight Drives
    Posts
    7,742

    Re: What's wrong with my 8.1 Horizon Engine?

    Yep - Air, Spark, Fuel.
    John

    2008 44 Sedan Bridge - Shell's Island II - Our awesome 44!
    2005 340 Sundancer - Shell's Island - The perfect 340! - TRADED!
    1997 250 Sundancer - Hampton's Inn - SOLD!

  5. #5
    Join Date
    Dec 2008
    Location
    Sarnia, Ontario, Canada
    Boat
    Sea Ray
    Details
    340 Amberjack
    Engine(s)
    twin 8.1S 370 Hp + 4.5 Westerbeke Genset
    Posts
    1,468

    Re: What's wrong with my 8.1 Horizon Engine?

    Regarding fuel... Would a spin on fuel filter/water separator get clogged enough to affect the engine in this way, and if so, would the affect not worsen over 30 hrs of use?

    By the way, my engines do not have any other filter (like an in-line or cool fuel filter).
    Posted by Jim of "Island Rhythm"
    2001 Sea Ray 340 Amberjack
    LOA 38', approx 18,000 lbs & 13.5' Beam
    Straight Shaft Drives


  6. #6
    Join Date
    Oct 2007
    Location
    Washington Park Marina, Michigan City
    Boat
    Sea Ray
    Details
    '07 340 DA, E80, Vessel View, Soft Top '12 Boston Whaler 15 Montauk
    Engine(s)
    8.1 Mercruiser V-Drives, Mercury 60 HP Bigfoot
    Posts
    11,514

    Re: What's wrong with my 8.1 Horizon Engine?

    When I had fuel issues with clogging (still po'ed at Harbor Isle, St. Joseph for that one) it manifested itself with surging, swinging 300-500 RPM's erratically.

    My friend's 340 (2003) last year was exhibiting issues like yours, and a plug change cured it. He also had one spark plug wire that burned through the insulation and was arching.
    Scott of the most excellent Sea Ray "Destiny".
    "There's only two things that excite a man, expensive toys and real expensive toys."




    Quando omni flunkus moritati
    Previous boats: '03 320 DA, '01 280 DA, '95 270 DA, '81 260 DA, '87 230 WE, '66 Boston whaler 13 sport, '75 BW 13 Sport, '87 BW 15 Supersport, '09 BW 15 Supersport and a couple of dinghies.

  7. #7
    Join Date
    Aug 2008
    Location
    Madison, MS
    Boat
    Sea Ray
    Details
    2001 380 DA
    Engine(s)
    T8.1 Horizons
    Posts
    1,199

    Re: What's wrong with my 8.1 Horizon Engine?

    Had the same problem last year....change the plugs.
    Southpaw II
    2001 380 DA
    Madison, MS

  8. #8
    Join Date
    Dec 2008
    Location
    Sarnia, Ontario, Canada
    Boat
    Sea Ray
    Details
    340 Amberjack
    Engine(s)
    twin 8.1S 370 Hp + 4.5 Westerbeke Genset
    Posts
    1,468

    Re: What's wrong with my 8.1 Horizon Engine?

    Plug inspection/replacement was second on my list. First was checking out the engine in the dark while running to see if there is a light show anywhere. To best reveal arcing should the engine be under load or just at a fast idle like 2000 rpm??

    From your description of fuel starvation, that's probably not it - but I'll be changing the filters anyway (but it's way down the list)).
    Posted by Jim of "Island Rhythm"
    2001 Sea Ray 340 Amberjack
    LOA 38', approx 18,000 lbs & 13.5' Beam
    Straight Shaft Drives


  9. #9
    Join Date
    Oct 2007
    Location
    Washington Park Marina, Michigan City
    Boat
    Sea Ray
    Details
    '07 340 DA, E80, Vessel View, Soft Top '12 Boston Whaler 15 Montauk
    Engine(s)
    8.1 Mercruiser V-Drives, Mercury 60 HP Bigfoot
    Posts
    11,514

    Re: What's wrong with my 8.1 Horizon Engine?

    http://cgi.ebay.com/ebaymotors/AC-De...item45f0728b82

    I bought 16 plugs from this guy for $47.60 shipped. They are new.
    Scott of the most excellent Sea Ray "Destiny".
    "There's only two things that excite a man, expensive toys and real expensive toys."




    Quando omni flunkus moritati
    Previous boats: '03 320 DA, '01 280 DA, '95 270 DA, '81 260 DA, '87 230 WE, '66 Boston whaler 13 sport, '75 BW 13 Sport, '87 BW 15 Supersport, '09 BW 15 Supersport and a couple of dinghies.

  10. #10
    Join Date
    Dec 2008
    Location
    Sarnia, Ontario, Canada
    Boat
    Sea Ray
    Details
    340 Amberjack
    Engine(s)
    twin 8.1S 370 Hp + 4.5 Westerbeke Genset
    Posts
    1,468

    Re: What's wrong with my 8.1 Horizon Engine?

    Quote Originally Posted by sfergson727 View Post
    http://cgi.ebay.com/ebaymotors/AC-De...item45f0728b82

    I bought 16 plugs from this guy for $47.60 shipped. They are new.

    WOW - that looks like the lowest price we'll likely ever see. I'm going to order my 16 as well. Thanks!

    What did you put in as an "offer" to get that deal?
    Posted by Jim of "Island Rhythm"
    2001 Sea Ray 340 Amberjack
    LOA 38', approx 18,000 lbs & 13.5' Beam
    Straight Shaft Drives


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