Less than acceptable performance

Discussion in 'Powerboats' started by bluesfan1, Aug 26, 2015.

  1. bluesfan1
    Joined: Aug 2015
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    Location: St Charles, MO

    bluesfan1 New Member

    I've recently purchased a 2015 Bennington 2275 GCW with the express triton package. It has a Yamaha 150hp motor. Before I purchased it I contacted Bennington and talked to the dealer about what kind of speed I could expect. Both estimated that 39 mph was a very real possibility but 40 was probably out of the question. To be honest I'm more concerned with the speed at about 3/4 throttle.

    First time out we maxed out at about 28 mph and the rpms were at 5800. The dealer replace the prop saying that it had the wrong one on it. Now we do a little better about 31 mph but the rpms are maxing out at 5200-5400.

    Can the height of the motor be an issue? A friend told me that he thought it might be too low. I've always had an I/O engine for the last 20 years so outboards are new to me.

    Any ideas would be very much appreciated.
     

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  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Welcoemn to the forum.

    Well need a bit more information and additional photos to help much.

    The first thing we'll want to see is the ventilation plate height, in relation to the bottom of the boat. Trim angles at WOT, recommend RPM at WOT, current prop spec's, etc. As a rule pontoon boats aren't going to perform nearly as well as other hull shapes, but I'll bet on the prop being wrong, as your engine should turn in the 5,700 - 6,000 range. I think you've fallen victim to a few things, the first - that salesmen don't know crap about what they're selling you and will tell you anything they think you need to hear. Second, the boneheads that work at the place you bought it (the mechanics) really only know how to install a part, not what it will do or if it will really help solve your issues. If the new prop has you pulling 5,400 RPM, the prop is "biting" too hard and needs to be "relaxed". A couple inches less pitch will probably do, though cup and blade type can also come to play. It's unlikely the guys you're dealing with can do this with assurance, other than trying different props in a hit or miss fashion, until they nailed it.
     
  3. philSweet
    Joined: May 2008
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    There is a Youtube with very high production values done by a magazine that reports 40 knots. Find out what the setup was. It may take a while to break the motor in, by the way. These things come from the factory detuned a bit, and may need a pretty thorough going through after 100 hours of break-in. The factory timing on my smaller Yamaha was out by a mile. I spent an entire day dialing it in after break in. Then never touched it again.

    Yours does have the new oval pontoons, yes?
     
  4. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    I don't know that the engine can be blamed here, if it is only getting to 30 mph tops. It seems to be revving out well enough, into the ideal range. What are you gauging the speed from, GPS ? And the "will get to 39 mph but 40 mph is out of the question" sounds like a joke of some kind ! I'd be interested to hear what the propellor pitch is. It is hard to imagine it will rev to 5800 and 29mph flat chat, and not be running a fairly low pitch. Something does not add up here.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    Maybe it has too much in-trim, but it was trimmed down too far, it wouldn't be getting to 5800 with a prop well matched to the boat.
     
  6. JR-Shine
    Joined: May 2004
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    Location: Vero Beach, FL

    JR-Shine SHINE

    check the manual, my F250 max range was 5800 to 6200 and you need to be able to hit those RPMs or else you run the risk of damaging the motor.

    You have a big bimini top or a heavy load?

    Motor might need to come up a notch. Hold a straight edge under the keel and see where it hit the motor, take a picture of that and post it here.

    Joel
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    I assume this is the boat, http://yamahaoutboards.com/sites/default/files/bulletins/BNT_2275GCW_F150LA_2014-10-28_PNT.pdf
    Going on that, it peaked @ 5800 rpm doing 40 mph, with a 15" pitch prop. This is why I find it a puzzle how he got a reading of 28 mph at peak revs of the same 5800 rpm. The only way that could happen is if it has a much lower pitch, and the boat is handicapped by excess load, or severe in-trim, or motor set too low. But it probably came with the 15" prop originally, so I question the speed reading.
     
  8. bluesfan1
    Joined: Aug 2015
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    Location: St Charles, MO

    bluesfan1 New Member

    Thanks for the help

    I'm hoping to get back up to the lake this weekend where I can maybe get some more pictures and information.

    My boat is a tri-toon and they are not elliptical. The elliptical toons are upgrades and our budget couldn't fit it in. Also we bought it straight off the showroom floor and it wasn't equipped that way.

    The 5800 rpm and getting 28 mph was definitely using the wrong prop. I can't tell you what it was but I know that we currently are using a reliance 15 - 14 1/2.

    As far as load we have a decent amount of gear on the boat but it's not that heavy.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

  10. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    Maybe that's the problem. Are there any tests with the round toons?
     

  11. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    The last link I provided was with the tri-toon, and the pontoons are described as SPS (?) whereas in the other link, they were described as elliptical. Whatever the case, as I said earlier, the data does not add up.
     
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