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Thread: Need help with questions/advice about a 1996 16

  1. #31
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    Quote Originally Posted by John C in PA View Post
    It looks like we're starting to get to the facts. Are you sure your tach is reading correctly? (During my Repowering the shop found mine was good up to a certain rpm, then went 1000 rpm low). Are you using gps for speed? I don't have a Merc drive but the reduction ratio may be stamped or noted on a tag.

    Using your numbers, prop slip is an impossible -20%. At a 1.5 ratio, slip is a reasonable 10%. Is the engine unable to turn faster than 4100 rpm? Sound starved? Hiccups? Something is wrong with the numbers. You should get minimum high 50's with 400 hp and a 21" prop.

    My oem 5.0 HO best ever, cool day, alone and half tank of fuel, was 59.8 GPS @ 4,850 rpm using a tweaked SST 21" prop. Best info I could find says I had 200 HP from that engine.

    John C
    I am using the GPS for speed and feel like my tach is accurate.
    Keep in mind that I had my trim all the way down, and the tabs were down some also. I did not trim it out to get to the top speed, I will though and post those numbers after I do.
    I was on here looking for tips on trimming and tabbing to get to top speed safely so we're getting a little ahead for where I am currently.

    I will say that I'm very excited to have so many people giving advice and helping me learn as I go.

  2. #32
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    Here is what I did when I got my Sweet 16. I went out on a lake during the week (fewer jet skis to annoy you &#128520. Tabs all the way up. Pick a comfortable cruising rpm. Run the drive slowly up and down watching the trim gauge, the tach, the speedo, and the angle of the bow to see the effect of the different trim positions. The effect of the drive angle to the water will be obvious in speed @ rpm.

    Then, set the drive to midrange, set a cruising speed, run the tabs slowly up and down, check the tach, the gps, and the bow angle as above.

    Once you you pretty much realize how these devices affect the performance and handling you can decide for yourself to use the tabs or not.

    Good luck.

    John C
    '
    92 Sweet 16 302 Ford
    Windshields are for Sissies!!!

  3. #33
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    Quote Originally Posted by 45171 View Post
    What is "slip" and what else do you need to know from me?
    A prop is like a machine screw. In a solid substance a 21" pitch prop would advance 21" per revolution. However, water is not a solid substance and propulsion comes from the difference in pressure between the font and rear of the blades. So a 21" prop with 0% slip would provide 56 mph, but at a realistic 10% slip you can only achieve 50 mph.

    The calcs aren't a be all, end all but rather a part of understanding the Black Magic of prop selection.

    John C
    '
    92 Sweet 16 302 Ford
    Windshields are for Sissies!!!

  4. #34
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    heres a prop calc

    http://www.rbbi.com/folders/prop/propcalc.htm running your numbers at 1.47 4100 rpm 21 pitch 49 mph your at 11%
    When the sky is grey,look out to sea.
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  5. #35
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    [QUOTE=John C in PA;668606]Here is what I did when I got my Sweet 16. I went out on a lake during the week (fewer jet skis to annoy you ). Tabs all the way up. Pick a comfortable cruising rpm. Run the drive slowly up and down watching the trim gauge, the tach, the speedo, and the angle of the bow to see the effect of the different trim positions. The effect of the drive angle to the water will be obvious in speed @ rpm.

    Then, set the drive to midrange, set a cruising speed, run the tabs slowly up and down, check the tach, the gps, and the bow angle as above.

    Once you you pretty much realize how these devices affect the performance and handling you can decide for yourself to use the tabs or not.

    Good luck.

    John C[/QUOTE

    Great info again and again John! I tend to over think things and what you're telling is gonna help tremendously. This is sort of what I did, only adjusted the tabs and didn't touch the trim.

    This brings up another question about turning. The lake I live on (Lake Waynoka OH 45171) isn't really wide and I've already been concerned about what will happen if I turn too sharp/fast. Is there any reason for me to be seriously concerned and slowing down to under 20MPH to make a turn or will this boat cut thru a 180 turn and keep cruising without any concern?

  6. #36
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    Quote Originally Posted by mattyboy View Post
    heres a prop calc

    http://www.rbbi.com/folders/prop/propcalc.htm running your numbers at 1.47 4100 rpm 21 pitch 49 mph your at 11%
    You have read my mind Sir thank you!

    From what I've read here theres opportunity to get that 11% down some by being more efficient with the trim settings.

  7. #37
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    [QUOTE=45171;668615]
    Quote Originally Posted by John C in PA View Post
    This brings up another question about turning. The lake I live on (Lake Waynoka OH 45171) isn't really wide and I've already been concerned about what will happen if I turn too sharp/fast. Is there any reason for me to be seriously concerned and slowing down to under 20MPH to make a turn or will this boat cut thru a 180 turn and keep cruising without any concern?
    Yep, too fast and too tight and you can roll the gunn'l into the drink. Remember: seat time is your friend . And don't forget to lower the drive as you start the turn to keep the prop blades in the water.

    John C
    '
    92 Sweet 16 302 Ford
    Windshields are for Sissies!!!

  8. #38
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    tuck your drive back in and pull up your tabs if theyre down.

    You will learn to love biting hard and gunwhales down, and used to being on the low side ( as well as the high side ) while doing this.

    From personal experience with a member here in TEXAS he used to throttle back from 65-70, down to 40's and lock the steering one way or the other and get off the throttle.

    It was quite interesting but the boat didn't seem to care. We did that many many many times in Possum Kingdom Lake. It performed like a jet ski.

    The boats seem to have more balls than the driver does IMO ..



    Drive down, tabs up in TURNS then reload and set it up again. ( or just don't use your tabs period )

  9. #39
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    IMO the term 'drive down' should not be confused with 'drive in' . If you've been running with a fair degree of positive trim all you really need to do is just level the drive with the keel , at most .
    Trimming to far in , especially if combined with suddenly chopping the throttle , will encourage a spin out .
    Just because something's old doesn't mean you throw it away !

  10. #40
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    word to MC

    it is not a step hull but trust me you don't want to bow steer and stick the nose especially with drive in/ trim down or tabs down.

    you may ventilate or cavitate depending on the prop but leave the trim nuetral my 16 was set nuetral all the trim manually no tabs all the way up



    I could do an about face turn at cruise speed in about 400 foot radius without staining the shorts

    as John said seat time drive within what you feel comfortable
    When the sky is grey,look out to sea.
    When the waves are high and the light is dying,
    well raise a glass and think of me...
    When I'm home again,
    boys, I'll be buying!

    My Ride

    Come Join Us on The Queen Of American Lakes



    Contact Us

    www.lgdonziclassic.com

  11. #41
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    Quote Originally Posted by mattyboy View Post
    word to MC

    it is not a step hull but trust me you don't want to bow steer and stick the nose especially with drive in/ trim down or tabs down.


    Aye , I thought about including the phrase 'even if this isn't a stepped hull ' but I figured that with the level of experience here many people would have experienced the pitfalls of executing a turn in a deep V hull that wasn't correctly trimmed in the right water conditions and the bow ended up catching.
    Just because something's old doesn't mean you throw it away !

  12. #42
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    Quote Originally Posted by Morgan's Cloud View Post
    IMO the term 'drive down' should not be confused with 'drive in' . If you've been running with a fair degree of positive trim all you really need to do is just level the drive with the keel , at most .
    Trimming to far in , especially if combined with suddenly chopping the throttle , will encourage a spin out .
    I don't get the difference in"drive down" & "drive in". Can you please go into a little more detail?

  13. #43
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    Lots of good info here!

    Everyone has provided a lot of great info here. I agree, keep your tabs up. I only use mine to level the ride at lower speeds when I have an uneven load (read that as one of my heavier friends in the port side seat ).

    Regarding a rub rail in the water, that's pretty common with the 16 and 18 classics. You'll get used to it but some of your passengers may not.

    rub rail in water.png

    For sharper turns do what was recommended above, pull your trim on the outdrive in but don't over do it. I bring it in less than half way and haven't had an issue of blowing out the prop.

    '07 22 Classic Shelby GT
    '96 18 Classic - sold
    '69 16 Ski & Sport - sold


  14. #44
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    Quote Originally Posted by 45171 View Post
    I don't get the difference in"drive down" & "drive in". Can you please go into a little more detail?
    Once upon a time the early Merc instrumentation trim indicator gauge had a designated area that showed 'negative trim' and had the word 'in' on it . That area on the gauge represented where the outdrive was past the level with the keel position and the propshaft was imitating the angle that a straight inboard shaft would look like . (although not quite as dramatic)

    Essentially the outdrive goes through 4 different positions .
    1) 'In' .. almost never used except to get a boat that's hard to plane up and going OR maybe certain weather conditions to keep the bow down ( but here I like to use neutral trim and use the tabs )
    2) 'Level' or 'Neutral trim . Anti ventilation plate/propshaft level with the keel
    3) 'Positive trim' for getting the bow up and more speed
    4) 'Tilt' raising the drive all the way up for beaching or trailering .

    To me , 'drive down' is any position that you can safely run the unit in that doesn't stress the U joints and can include the 'in' position but the 'in' position should never need to be used once the boat is over the hump and planing .
    Just because something's old doesn't mean you throw it away !

  15. #45
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    Quote Originally Posted by Morgan's Cloud View Post
    Once upon a time the early Merc instrumentation trim indicator gauge had a designated area that showed 'negative trim' and had the word 'in' on it . That area on the gauge represented where the outdrive was past the level with the keel position and the propshaft was imitating the angle that a straight inboard shaft would look like . (although not quite as dramatic)

    Essentially the outdrive goes through 4 different positions .
    1) 'In' .. almost never used except to get a boat that's hard to plane up and going OR maybe certain weather conditions to keep the bow down ( but here I like to use neutral trim and use the tabs )
    2) 'Level' or 'Neutral trim . Anti ventilation plate/propshaft level with the keel
    3) 'Positive trim' for getting the bow up and more speed
    4) 'Tilt' raising the drive all the way up for beaching or trailering .

    To me , 'drive down' is any position that you can safely run the unit in that doesn't stress the U joints and can include the 'in' position but the 'in' position should never need to be used once the boat is over the hump and planing .
    Man....I've pretty much always driven with the trim all the way in/down unless I get into really shallow water or larger than normal waves.
    I am going to have to search for info on how to be using the trim and learn what I thought that I already knew.

    I found this gauge face picture that I was using to help follow what you are explaining. If I'm understanding correctly, where the blue meets the orange is what would be considered neutral, and this is the position that is going to be the most efficient to run.

    Is this also true for pretty much any boat in normal conditions?
    And is the orange area where the u-joints start to have problems?
    Are the black dots representing anything specific or just there to help reference the position so it's easier to return to it later?

    My apologizes of it's too small to view clearly, I found it on eBay and could get a larger image.

    Capturetrm.PNG






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