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  • Something's not right here

    I just purchased a used 2010 Tahoe Q4 SS (18') with a Mercruiser 4.3L (4 barrel) 190 hp. The market for used boats where I live is very competitive and there was no opportunity for a water test prior to purchase. It has what I believe to be the stock prop (3 blade aluminum, not sure of the pitch or size).

    The boat has very poor performance though the engine seems to perform normally. When accelerating I have to rev up to to max RPM (4800) to get the boat on plane and it will only do about 21 mph when trimmed out at that RPM. I have to be careful not to over rev the engine as I hit 4800 RPM at roughly 3/4 throttle.

    My initial suspicion was the prop but now I am thinking it might a damage hub or worse, something in the drive itself. I am looking for advice from anyone who has experience a similar issue or some guidance on how to figure out what the issue is.

    Thanks
    John

  • #2
    welcome aboard

    first, verify your speed with a GPS, the dash speedos are notoriously inaccurate

    next, what prop do you have on there. we cant help you much more than stating we need that information

    it most likely isnt the drive, because if it was, it wouldnt last more than a few minutes

    it could be your prop hub. take a sharpie and draw a line across the prop and the prop nut. go for a ride. if the line on the nut moves with respect to the line on the prop, you have an issue

    it could also be your coupler.
    Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

    1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

    Past Boats
    1970 Wooster Hellion - Merc 9.8
    2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
    1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

    What’s behind you doesn’t matter.Enzo Ferrari

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    • #3
      If motor, prop and coupler are found Ok, distribute deck load evenly as will be loaded and trim the motor for combo to ride parallel to water level once on plane, report new wot run rpm with said condition. Will be interesting to see which wot rpm the motor dials to go from there..

      Happy Boating


      Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

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      • #4
        You sure about engine as the Q4 was only offered with a 135hp from the brochures listed????
        When in doubt,Trim it out!!!
        Business Owner & Certifed Technician
        Boats I own & use
        20ft Javlin w/250 Junkrude
        17ft Bullet w/200 Merc (SOLD!!)
        13ft Allison w/150 I-6
        17ft Hydra-Sport 175GT
        15ft Allison w/75 Stinger(project)
        14 x 48 Drifter with 1100SS Merc

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        • #5
          The prop is a 3 blade aluminum 14 1/4 x 21". I went into the local Bass Pro yesterday and they did search on my Hull ID. The boat originally came with a 3.0L 4 cylinder engine. Obviously someone replaced it with the 4.3L so now I don't know anything about my engine year. I pulled the boat out of water last night and brought it home so now I can't do the mark and run test to see if they hub has spun. I pulled the prop off and everything look normal the hub slides into the prop and I can't turn it by hand, it appears to be a Flo Torq II to me from what I can see online. I put the prop back on and put the boat in gear with the motor off. It would turn one way with a click but not the other at all.

          If it's not the prop hub what's my next step?

          Thanks
          John

          Comment


          • #6
            Find out if the 4.3 in it is a Marine engine, or just any old Auto/Truck Engine from a Wrecker

            Comment


            • #7
              Sounds like they didn't change the drive ratio.....
              When in doubt,Trim it out!!!
              Business Owner & Certifed Technician
              Boats I own & use
              20ft Javlin w/250 Junkrude
              17ft Bullet w/200 Merc (SOLD!!)
              13ft Allison w/150 I-6
              17ft Hydra-Sport 175GT
              15ft Allison w/75 Stinger(project)
              14 x 48 Drifter with 1100SS Merc

              Comment


              • #8
                I found the serial number plate on the engine last night and searched it online. The engine is a 1992 4.3 LX (4 barrel) so it is a real marine engine. At least now I can order parts for the engine issues.

                I still don't have any idea how to try to resolve the drive issue. I had a good look that the drive unit last night, it is an Alpha One gen 2 with a 2.00 drive ratio. From all appearances it appears to be the original drive that came with boat and the 3.0L engine.

                Faztbullet, or someone else could you please elaborate on changing the drive ratio???

                Thanks
                John

                Comment


                • #9
                  Find a Gen 2 upper in 1.81 ratio...…Google sterndrive sei
                  When in doubt,Trim it out!!!
                  Business Owner & Certifed Technician
                  Boats I own & use
                  20ft Javlin w/250 Junkrude
                  17ft Bullet w/200 Merc (SOLD!!)
                  13ft Allison w/150 I-6
                  17ft Hydra-Sport 175GT
                  15ft Allison w/75 Stinger(project)
                  14 x 48 Drifter with 1100SS Merc

                  Comment


                  • #10
                    The gear ratio won't effect the issue you are having and there is no problem running your current set up once propped to wot rpms. The issue is you are getting 56% slip with your current set up. First step verify tach is reading properly and GPS speed. Check for prop hub slip or engine coupler slip.

                    Once you get the slip under control running a 2 higher pitch prop will make up for the difference in gear ratio. If the 1.81 takes 21p to run at wot rpms then the 2.0 will be 23p for similar results.

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                    • #11
                      Sign up today
                      TF,

                      Plainly in agreement, gear ratio is relative, a matter to play with correct prop pitches till motor achieves it's max wot revs as loaded...

                      Happy Boating


                      Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

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