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  1. #1
    Member
    Join Date
    Mar 2011
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    Shelby, AL
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    33

    What effect does motor height have on attitude (bow lift, porpoising, etc)

    G3 Eagle 175 (920 lbs), Yamaha 90 four stroke, Yamaha K series aluminum prop - 12 5/8 x 21

    WOT 5,900 rpm - 43 mph, good hole shot, comfortable cruise 3,800-4,000 rpm @ 26 mph or so. I like everything about it except excessive bow lift at slower speed, it comes off plane around 3,200 rpm and bow lifts so much I can't see over it.

    Motor is in second hole from top, cav plate is dead even with keel. What effect does motor height have on attitude? Would raising the motor have any effect on slow speed bow lift?

    Now the rest of the story! I installed a SE Sport 400 no-drill hydrofoil thinking that might help, and it did help with bow lift, it stays on plane down to appx 2,800 rpm. But it had a terrible effect on performance, I can't trim up enough to get it out of the "plowing" attitude without porpoising like crazy.

    Trim tabs are not an option for me.

  2. Member
    Join Date
    Jul 2014
    Location
    Crossville, TN & Houston, TX
    Posts
    3,466
    #2
    Smart Tabs.

    Most every tab system, not just Smart Tabs, are designed exactly for your issue.

    I put them on 3 boats. Inexpensive and, more importantly, they work.

    Look at high quality flats boats. They pretty much all are equipped with a Tab system when purchased. Flats boats have to "get up" in shallow water all day, every day.

  3. Member Big Al's Avatar
    Join Date
    Mar 2005
    Location
    WG, Maine
    Posts
    5,348
    #3
    Jim,

    I notice you have a 90 Four stroke. I believe the HP rating for that boat was a 2 stroke (2010 model yr or earlier). A 90 2 stroke is about 100 lbs lighter. That extra 100 lbs on the transom could be adding to your problem?
    2018 G3 Sportsman 17 90 SHO

  4. Member
    Join Date
    Mar 2011
    Location
    Shelby, AL
    Posts
    33
    #4
    Quote Originally Posted by Big Al View Post
    Jim,

    I notice you have a 90 Four stroke. I believe the HP rating for that boat was a 2 stroke (2010 model yr or earlier). A 90 2 stroke is about 100 lbs lighter. That extra 100 lbs on the transom could be adding to your problem?

    I’m sure it is, I know it’s stern heavy. I raised the motor two holes, which is all the way up, and it’s working good. Can trim it up now without excessive porpoising and WOT is 6,000 rpm. Looks like it picked up a couple mph and slow speed bow lift is way better, stays on plane down to 2,600 rpm now and even after it dry off plane the bow is lower. So far I’m liking it.