Results 1 to 9 of 9

Thread: water spraying over transom into boat

  1. #1
    Member
    Join Date
    Jan 2010
    Location
    Kenai, AK
    Posts
    150

    Default water spraying over transom into boat

    I have a 1648 MV Jon w/jet tunnel and a Yamaha 40/30 o.b. jet (tillar steering). With me, the motor, fuel and battery all in the back 1/3 of the boat I'm pretty stern heavy so I had the builder weld on brackets for trim tab installation w/o having to drill through the transom.
    The brackets are just aluminum channel welded horizontally where you'd normally drill through the transom to mount the Nauticus Smart Tabs SX
    http://www.nauticusinc.com/smart_tabsSX.htm

    They work great, the boat jumps on plane no problem without hardly any weight in the bow to counter the stern weight (not so when I have them in the retracted position... I bought this http://www.nauticusinc.com/pr500.htm so I could get them out of the way when they aren't needed/wanted needed). All is good from just putting along to just after coming on plane (about 1/3 throttle)... untill I start opening up the throttle beyond 1/3. Water starts spraying directly up the transom, the spray on the two outboard sides is mostly harmless if not irritating but the stuff that gurgles in between the motor and transom is a nuisance at best and potentially dangerous if a guy weren't paying attention. I had to stop about every 15 minutes and bail 2-4 gallons out. As a stop gap (and because I want one anyway) I'll be adding a bilge pump.

    My only theory (hypothesis really) is:

    As the tab cylinder is compressed to the point that the tab is parallel to the water it somehow causes the spray by just sort of skimming the surface.

    Possible solution- I need to increase the cylinder pressure by moving to another mounting position (it has five mounting positions to vary cylinder pressure. This should keep the tab-end just below surface at full speed, as it is when I currently come on step.

    Problem with solution- I may be causing more resistance than is needed to get on step, slowing the boat down a little. That would be acceptable if it works. I could also remove the trim tabs when I'm hauling weight in the bow.

    What do you think?

  2. #2
    Member
    Join Date
    Jan 2007
    Location
    Southwest Alaska
    Posts
    2,145

    Default

    Have you had someone drive the boat while you sit in back to see where the water is coming from?
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

    Better living through chemistry (I'm a chemist)

    You can piddle with the puppies, or run with the wolves...

  3. #3
    Member
    Join Date
    Dec 2009
    Location
    lower u.s.
    Posts
    91

    Default

    you need a plate that goes from the bottom of the boat out and over the top of the jet foot extending some over the sides of it. that will take care of it. probably the most water is coming up and hitting the top around over the jets foot and shooting up into the boat. common problem, easy solution..
    your motor will perform much better as well. and you wont need the trim tabs.

  4. #4
    Member Alasken's Avatar
    Join Date
    Apr 2006
    Location
    Eastern Oregon
    Posts
    457

    Default

    The most common cause of excessive spray running an OB jet is that the engine is mounted too low.
    I've run a lot of OB jet boats and have never seen a need for trim tabs. I have relied on weight distribution though.
    Art is making something out of nothing and selling it.
    - Frank Zappa

  5. #5
    Member Akgramps's Avatar
    Join Date
    Apr 2008
    Location
    Last civilized place on the planet
    Posts
    2,080

    Default

    I wondered the same thing, maybe needs the UHMW to cover the gap between the tunnel and the foot.................
    But, I read it again I think Wyboo is talking about water coming off the sides of the trim tabs?...........Wyobohunter, can you clarify.......?
    Trim Tabs just seem like a bad idea on a river boat............IMO...can you adjust the tabs so when in the up posistion they are not touching the water?

  6. #6
    Member Crumm's Avatar
    Join Date
    Apr 2006
    Location
    Fairbanks, AK
    Posts
    505

    Default

    Best solution in my opinion would be to trade the trim tabs for a longer fuel line and battery cables. Trim tabs on a riverboat have a very short life expectancy and it sounds like yours are about to sink you. Weight distribution is a better way to trim a small boat.

  7. #7
    Member
    Join Date
    Jan 2010
    Location
    Kenai, AK
    Posts
    150

    Default

    Quote Originally Posted by Crumm View Post
    Best solution in my opinion would be to trade the trim tabs for a longer fuel line and battery cables. Trim tabs on a riverboat have a very short life expectancy and it sounds like yours are about to sink you. Weight distribution is a better way to trim a small boat.
    I've thought about this... The tabs I have can be set up even with the bottom of the boat so shallow running shouldn't be an issue. Time will tell.

    I forgot, my first trip out I didn't have the problem but I was riding a little bow high so I trimmed the intake in toward the transom; the next time I went out the problem appeared. After reading some of the replies I remembered this and have put the motor back to its' original position and adjusted the tabs pressure to keep the bow down. I'm going dipnetting tomorrow so I'll see how it works out.

    Thanks for all of the replies.

  8. #8
    Member Frostbitten's Avatar
    Join Date
    Jun 2010
    Location
    Alaska - I wasn't born here, but I got here as soon as I could!
    Posts
    3,279

    Default

    One other thought, you said the problem doesn't occur until you are already on step and opening up the throttle. Once on step, I would think you could maintain whatever bow height you wish by trimming the motor. If so, can you retract the tabs so they are completely out of the water?

    In any case, like Nitro said, have someone run the boat so you can ID exactly where the spray is coming from.

  9. #9
    Member
    Join Date
    Jan 2010
    Location
    Kenai, AK
    Posts
    150

    Default problem solved

    I returned the motor to the original position and the problem went away, then I adjusted the trim tabs and got the bow down. Thanks for the replies. I still may get that plate that fills in the area between intake and transom.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •