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2001 216SSi speed problem

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  • 2001 216SSi speed problem

    Hey guys, I have a question on my 216SSi and I hope others can shed some light and/or provide some comparison. I recently purchased a 2001 216SSi project boat. The engine has been damaged due to lack of winterizing so I took it out and went completely through it. It was originally a GSi engine but the previous owner believes he replaced it with a GXi. Of course, it is essentially a 5.7 Chevrolet Vortec. It has 1.6 roller rockers and an Edelbrock dual plane intake under the original TBI unit. He claims that it would not run out on the top end until he put a GXi fuel pump on it, which he did at some point. The only modification I made to it was to drop the compression by a half point due to the well known detonation problem on these motors and the fact that this one had severely tuliped valves and cracked ring lands on the pistons. Overall the engine at this point should be putting out somewhere between 300 - 320 hp (original GSi was rated at 280)

    The boat now seems to run fine, but will only achieve about 44 mph at 4300 rpm with only myself, my daughter, and a full tank of fuel, at 800ft lake elevation. It has a 14 3/4x19 single three blade Volvo Penta prop, seems like others have gotten a lot more speed from their boat with even bigger props. Of course, I am thinking about putting a 17 inch prop on it to get a little more rpm and speed (and better holeshot), but wanted to ask of others what they have achieved in terms of speed and rpm, and their engine and prop specs.

    All responses appreciated!

  • #2
    Re: 2001 216SSi speed problem

    Hello

    I also have a 2001 216 Ssi but mine has a 350 mag mpi bravo 3. I get 50 on the nose with light to medium load on gps. I hit 5000 but barely. I've dropped three prop sizes from a 28 dual to 4 bladed 24p duals. I would think a modest boat like this with 300 factory ponies should do more than 50. Sid you ever solve your power/speed issues?

    Thanks

    Brian

    Hartwell ga

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    • #3
      Re: 2001 216SSi speed problem

      Originally posted by bbrohm View Post
      Hello

      I also have a 2001 216 Ssi but mine has a 350 mag mpi bravo 3. I get 50 on the nose with light to medium load on gps. I hit 5000 but barely. I've dropped three prop sizes from a 28 dual to 4 bladed 24p duals. I would think a modest boat like this with 300 factory ponies should do more than 50. Sid you ever solve your power/speed issues?

      Thanks

      Brian

      Hartwell ga
      Well, I found out a few things:

      1. My speedo was off about 2-3mph - I did hit 46mph on GPS at 4400 rpm.
      2. Boat is running a little fat on the top end, about 11.5-12:1 AFR. I am in the process of tuning it, but haven't made much progress yet on getting it past 4400 rpm.

      It seems to hit a sort of wall at 4400 rpm, does not want to run past that. I would think especially with my prop (it is a little more of a holeshot prop than yours) it should run right up to the rev limit.

      BTW Brian, I am up in Greenville and we typically go out on Keowee, we should meet up some time, if not in the next couple of weeks, some time next season. I would like to see another Chap equipped similar to mine just to compare notes a bit.

      Comment


      • #4
        Re: 2001 216SSi speed problem

        Originally posted by timyerby View Post
        Well, I found out a few things:

        1. My speedo was off about 2-3mph - I did hit 46mph on GPS at 4400 rpm.
        2. Boat is running a little fat on the top end, about 11.5-12:1 AFR. I am in the process of tuning it, but haven't made much progress yet on getting it past 4400 rpm.

        It seems to hit a sort of wall at 4400 rpm, does not want to run past that. I would think especially with my prop (it is a little more of a holeshot prop than yours) it should run right up to the rev limit.

        BTW Brian, I am up in Greenville and we typically go out on Keowee, we should meet up some time, if not in the next couple of weeks, some time next season. I would like to see another Chap equipped similar to mine just to compare notes a bit.
        I haven't had the pleasure of boating Keowee yet. Might pull my boat from Hartwell and check it out if the water goes much lower. We live on Hartwell so we don't visit other lakes much.

        We are down over 11' and I only have 7' left under dock so with my lift my days are numbered til I need to pull the boat and put it somewhere else or on the trailer.

        I have great hole-shot and hit 5000 but I am disappointed I had to drop so many prop sizes just to hit proper wide open throttle RPM. Maybe this winter my Mechanic can find a smoking gun and hopefully its simple (coil, plugs, wires, etc). Prob wishful thinking.

        B

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        • #5
          Re: 2001 216SSi speed problem

          Update on my issue. I have done more tuning, and added a K&N flame arrestor (fancy name for air filter). Boat topped out at 53 at 4700 rpm on the GPS this past weekend - temperature was in the mid 70's, AFR at 4700 was about 12.5. She probably has another 1-2mph if I lean it out a bit more, but I ran out of laptop battery to do any more tuning. One thing I did notice, the alternator output is a bit weak, even running at 3000 rpm. Never really puts out more than about 12.8 volts. Might need a slightly bigger pulley there.

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          • #6
            Re: 2001 216SSi speed problem

            Originally posted by timyerby View Post
            Update on my issue. I have done more tuning, and added a K&N flame arrestor (fancy name for air filter). Boat topped out at 53 at 4700 rpm on the GPS this past weekend - temperature was in the mid 70's, AFR at 4700 was about 12.5. She probably has another 1-2mph if I lean it out a bit more, but I ran out of laptop battery to do any more tuning. One thing I did notice, the alternator output is a bit weak, even running at 3000 rpm. Never really puts out more than about 12.8 volts. Might need a slightly bigger pulley there.


            What did you have to do tuning wise to get the extra 300 RPM? Surely just the K&N didn't do all of that did it? I haven't done anything since we last chatted, but it's funny you mention the alternator. I haven't put a multimeter on it yet but my dash gauge reads low (often well below 12 at idle and barely 12 at speed). Two new batteries last summer. I also have noticed this year that my solenoid for the Captains Call Exhaust won't work unless over 900 RPM. I'm guessing it isn't getting enough juice at idle to operate.

            The tentative plan is to have my mechanic pull the motor and either rebuild it as a stout 383 (400+ HP) or replace it with as 427 small block and build up a bad-to-the-bone 450+ HP small block. My outdrive is rated for 425 so 450 would be about all I'm willing to throw at it. We'll see what the cost estimates come to but an extra 150HP with no weight gain should put me well over 60 MPH I would think.

            Boating this weekend and next (weather permitting) and then she'll probably come out for the winter.

            B

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            • #7
              Re: 2001 216SSi speed problem

              I have the software for tuning the engine air/fuel ratio, so most of the gains came from that. When I started the ratio was 11.5-12 to 1, which is not optimal for power, so I tuned it to 12.8-13.1 (I also have a wideband oxygen sensor for monitoring the AFR)which is more optimal. Actually I only modified it up to 4600 rpm because it had never gone over that, and it is still a little rich at 4700 (new top rpm) so it probably has 1-2 more mph in her once I finish the final adjustments.

              It's interesting to hear you confirm my suspicions regarding the alternator. I have never seen what I typically see on cars (13-14 volts), never achieving more than 12.5 volts. It wouldn't power my laptop charger due to low voltage last time I was out tuning. I had put two new batteries in her this year as well, always plugged in to a trickle charger when not on the lake. I may take a look at the truck engine I have in the garage and swap the alternator, it should put out a lot more juice.

              More cubes would definitely get you more power, I would be concerned about the tuning with the new engine as it will obviously need more fuel regardless of whether you go with a carb or fuel injection. One think I did when I built mine is a pulled out a half point of compression ratio. The previous owner had run with a lot of detonation as evidenced by severely cracked pistons and tuliped valves. I did some research and apparently that was a common warranty issue with those year GM engines because they increased the compression ratio and there was some issues with bad (ethanol) gas. When I was tuning mine I monitored the knock counts (detonation/knock sensor) and it never had any knock counts.

              I thought about going out once or twice more before putting it away, although my family seems dis-interested and I am not sure it is worth it to pull to the lake just so I can ride around alone (I live about 45 miles away on the NE side of Greenville), although it was very nice weather yesteday. My truck mirror thermometer was showing 81 degrees, although drizzling a little here now....

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              • #8
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                Re: 2001 216SSi speed problem

                Oh, by the way, I found some boat speed/rpm/hp calculators that seemed pretty accurate in my case, you might want to try some of those to see how much power it will take to reach your goals, although I will say 53 mph trimmed out feels a little unstable (I am sure it would be more stable with the nose in the water more, but that only gets me to about 48-49).

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