2005 nitro bay boat is this a design flaw?

Discussion in 'Powerboats' started by texas nitro, Jun 2, 2005.

  1. texas nitro
    Joined: May 2005
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: houston

    texas nitro Junior Member

    Taken on water and not planing, this is a brand new boat, It Has been doing this since i got it.
    I have taken it back to the dealer 4 times, they 1st changed motor said it had a pontoon motor with big foot lower end.
    installed the correct mercury 60 hp 4 stroke, 2nd trip raised engine 1 hole and took out trim pin, 3 rd tip raised engine 1 hole, 4th trip same.
    let me see if i can explain, the water is riding up the back of the boat in between the engine bracket and transome then coming into the boat at the top of the engine bracket where it makes it hook to the inside of the boat.

    I was Wondering if the engine was running too deep causing the bottom of the bracket to dig in?
    Is There anyway too visually tell where the motor should sat trimed all the way down in conjunction to the botom of the boat?

    The Plaining Problem Accualy got worse when i installed a tiger shark hydrofoil, it takes about 15 seconds to plain, and even that has to be worked.

    would a jackplate help?
     
  2. Willallison
    Joined: Oct 2001
    Posts: 3,590
    Likes: 130, Points: 0, Legacy Rep: 2369
    Location: Australia

    Willallison Senior Member

    What is commonly (but incorrectly) referred to as the cavitation plate should be a few inches above the bottom of the boat, the exact height will depend on how far aft of the actual transom it is. It should run clear of the surface when the boat's on the plane.
    What you describe certainly sounds like the engine is running too deep. If you can't raise the engine any further - not on the trim, but vertically, then I suspect you have a long-shaft (or extra-long) when you need a short-shaft outboard.
    Don't waster your money on a jacking plate - these are really only for high performance boats trying to eek out the last 1 or 2 mph.
    Personally, I'f take it back to the dealer and tell them you don't want it back 'till it's running properly. If they can't fix, get your money back and go to someone who knows what they're doing - by the sound of it, these guys don't
     
  3. Corpus Skipper
    Joined: Oct 2003
    Posts: 606
    Likes: 8, Points: 0, Legacy Rep: 173
    Location: Corpus Christi TX

    Corpus Skipper Hopeless Boataholic

    What size boat? 60 hp sounds a little low for a bay boat, which would cause slow planing.
     
  4. texas nitro
    Joined: May 2005
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: houston

    texas nitro Junior Member

    IT Is A 18 foot nitro same as kenner exept it has a 8 inch tunnel in the rear end.
     
  5. texas nitro
    Joined: May 2005
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: houston

    texas nitro Junior Member

    thanks, the guy from bass pro shop said its neither. said ther is no such thing on a 4 stroke?

    allso i looked at the cavatation plate today and it is level with the botom of the boat!! :eek:
     
  6. woodboat
    Joined: Nov 2003
    Posts: 312
    Likes: 1, Points: 0, Legacy Rep: 14
    Location: Baltimore MD, USA

    woodboat Senior Member

    "Level with the bottom of the boat" was always what I was told for standard boat packages. If running an HP prop then you could raise it up with a jack plate. I think 60 HP sounds a little low too. I had a 15ft with a 70hp. I wouldn't want anything under 100 for an 18. Is there anything hanging down into the tunnel? Oh and speaking of tunnel they can be designed to push water up to the prop and expect you to use a device like a jack plate to raise it up. Do you have a link to the boat hull?

    Ok I went out and found Nitro
    http://www.marineusainc.com/nitro/nitrobay/nitro_bay.htm
    If you look at the nitro 1900 VL you can clearly see the plate on top of the water. The water looks clean too. If you look at the 18 with rolled gunnels you see how disturbed the water is. It looks like 90 hp is the max HP as well.
     
  7. Willallison
    Joined: Oct 2001
    Posts: 3,590
    Likes: 130, Points: 0, Legacy Rep: 2369
    Location: Australia

    Willallison Senior Member

    Looking at the pictures on the website and given that the boat only weighs 990 lbs, and has a low deadrise hull, I would have thought that it would run ok with 60hp - it won't be a rocketship, but then it isn't designed to be...
    Either way - under-powered or not - it shouldn't be filling itself with water!
    Transom height is listed as 20" - check to see if this matches the shaft length of your outboard - I'd still hesitate a guess that you have an extra-long shaft motor on the back...
     
  8. Corpus Skipper
    Joined: Oct 2003
    Posts: 606
    Likes: 8, Points: 0, Legacy Rep: 173
    Location: Corpus Christi TX

    Corpus Skipper Hopeless Boataholic

    60 HP is WAY too small for that boat, I'd expect at LEAST a 115, most I see have 135 or better. Tunnels, pocket or otherwise, cause a slight suction on the hull sometimes, and also increase wetted surface, and therefore drag. I built the old Majek 15' scooter and they need 60 HP, 90 is optimal, and the tunnel on that boat doesn't pull suction as some do. As far as the spray, I still think you need a tunnel extension. I just put one on a 16' SkiBarge with a pocket that had the same problem (it had a 115 by the way) and it cured it.
     
  9. Willallison
    Joined: Oct 2001
    Posts: 3,590
    Likes: 130, Points: 0, Legacy Rep: 2369
    Location: Australia

    Willallison Senior Member

    Craig, the boats maximum rated hp is 90 - so whacking a 115 on it is not possible.
    I know this is an 18 footer - but it ain't exactly a big one. I still say that 60hp should push this boat comfortably. You may have seen a number of posts here by Tom Lathrop - and I'm sure he won't mind if I use his lovely boat "Liz" as proof of my point. She is 24' long and weighs 1850lbs w/o engine. With a 50hp 4-stroke she does 23mph. (see http://www.messing-about.com/smallboats/ ) The nitro is 18' long and weighs 990.
    Now I know things are never quite that simple - and I'm not familiar with the 'tunnel' that you refer to - but both are low deadrise planing hullforms.
    I had a 15' skiboat. The hull weighed around 950lbs - with a 90hp o/b it did 45 mph.
    Nope - I go back to my original post. Take the boat back to the dealer. If they can't fix the problem, get your money back and go somewhere else.
     
  10. Corpus Skipper
    Joined: Oct 2003
    Posts: 606
    Likes: 8, Points: 0, Legacy Rep: 173
    Location: Corpus Christi TX

    Corpus Skipper Hopeless Boataholic

    Ah, went and looked at the picture, not the Kenner I was thinking of. I think they rated it pretty conservatively tho, as I said most boats of that size and style around here have 115+.
    Gotta agree with Will there.
     
  11. texas nitro
    Joined: May 2005
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: houston

    texas nitro Junior Member

    Took The boat back to dealer yesterday, they said they would raise engine
    one more notch, it only has 1 more to go affter that.

    the cavatation plate was level with bottom of boat after they picked the engine up 3 times.

    Manager said he was affraid the boat would blow out if they picked it up any more.

    The boat runs at 28 mph with 2 passangers, myself,and a 1/2 tank of gas at WOT around 4800 rpms, Its My Understanding It should be around 5500-6000 rpms ?

    Under Power Or Not I Agree, It Should Not Take On Water When Coming of plain and it should'nt Take 15 Seconds to get it up on plain
    wiht a 60 4 stroke.

    if a 24 foot boat weighing twice as much will go 23 mph,Then what should a 18 foot with a 60 4 stroke do?

    I was told by the salesman at time of purchase it would do around 40,
    I talked to him yesterday and if raising the engine one more time does'nt fix thease problems, witch i doubt, then he,the tech, and the boating department manager are all going on a frusterating boat ride with me!!

    Taken it to the water this weekend, will let yall know .
     
  12. woodboat
    Joined: Nov 2003
    Posts: 312
    Likes: 1, Points: 0, Legacy Rep: 14
    Location: Baltimore MD, USA

    woodboat Senior Member

    here is the mercury 60hp efi http://www.mercurymarine.com/mercury_60_efi_fourstroke
    Claimed WOT rpm is 5500-6000. A prop is similar to a car transmission in that too large a prop is like too tall a gear. Imagine starting your car out in fourth gear. It would take a long time to get going but would produce a higher top speed. Starting in say second would provide more power with a lower top end. In your case it appears that the prop is too large for that small motor on the big 18 footer :) So acceleration is greatly reduced. Additionally it is so large that it is unable to reach desired WOT rpm. On my 15 fter I had two props, a 15 pitch for water skiing that reached 6500 RPM WOT and a SS 19 pitch that turned 5100 WOT but was 7 MPH faster but took much longer to plane. In concurence with the others I believe the dealers job is not finished.
     
  13. WilliamK
    Joined: Jun 2005
    Posts: 6
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Knoxville, AR

    WilliamK Junior Member

    Having some experience with this boat, I might offer a few suggestions.

    Take a straight edge and hold it to the bottom of the keel. The cavation plate of the engine ideally should be around 1/2 an inch above the keel bottom. The transom offset (pocket tunnel) will allow the highter elevation. Ideally, you should reach max rpm (5500-6000) with a light load, say one person and 1/2 tank of fuel.

    I think the boat should be running in the low to mid 30's. The Mercury F60 has a gear ratio of 1.83 to 1. I believe the proper pitch would be somewhere around 12-13". If you have the high thrust version of the Mercury 60, you will have a higher gear reduction, I believe 2.3 to 1, due to the different and larger lower unit on that motor. You will need a larger prop pitch, in the neighborhood of 15".

    When you are running the boat be sure to trim the motor out until the thrust of the engine is at least on a straight line with the keel. To much under tuck on the engine will help to get the boat on plane, but the boat will run much better on the top end by trimming the motor out some.
     
  14. texas nitro
    Joined: May 2005
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: houston

    texas nitro Junior Member

    SORY to sound stupid, but what is the keel :confused:
     

  15. WilliamK
    Joined: Jun 2005
    Posts: 6
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Knoxville, AR

    WilliamK Junior Member

    The center of the bottom of the boat, if you look at the bottom, place the straight edge along the bottom of the vee of the hull.
    Just curious, is this your first boat? If so, and if you don't have some prior experience driving an outboard, did the dealer give you any on water tutorial regarding the driving of the boat? The reason I am asking is that I have seen many times, a person not understanding the proper use of power trim on boats, many believe at first that the trim is intended only for tilting the engine when its on the trailer.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.