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5.0 OSi-E low power, unable to hit RPM & WOT.

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  • 5.0 OSi-E low power, unable to hit RPM & WOT.

    Background...I have been trying to troubleshoot this low power issue for a few weeks now. The motor while trying to get on plane basically stalls out at 3000 RPM until it finally gets on plane after about 10 seconds then maxes out at 4300 RPM. The boat is a Regal 2120 (21 foot boat I believe) and the engine is now a 5.0 OSi-E (serial 4012110198). The boat originally had a 4.3L GXi that I replaced in 2017 because it was ate up with salt water. So the outdrive (1.66:1) and prop (14 x 19) are the same as originally came on the boat so this thing should be giving us whiplash with the extra 45+ horsepower on the same drivetrain. In fact, in talking to Regal engineering, this is what they said:

    "The 2120 Destiny was built with a 50GXI. It used a 1.60 drive and a 21" prop. Top Speed was 53 MPH and O to 30 was 8.3 seconds on the one we tested. If he changes the engine the motor mounts will move forward of their present location by 4.5 inches.... he should be able to measure and see if the motor mount has an additional 4.5 inches but I believe it does. He could use the 1.66:1 drive he has but would likely need a 21 or possibly a 23" prop. Otherwise he would be on the Governor on the engine."

    I am not getting anywhere close. The boat sat in storage all last year since we moved and didn't have opportunity to get it out. Now this year, it just is not performing up to par.

    I bought MEFIscan to try and see what is going on. I have never used this software before so I am learning on the fly, but I don't see anything out of place...at least no codes, etc. I made a few runs today to get some data. I basically started at idle in gear and went to full throttle and then after the motor topped out (usually between 4000 and 4100 RPM, I then slowly brought the throttle back to idle. I made 10 or so runs and captured a few with MEFIscan and a few others with some different software that writes the data to a CSV file that can be opened by excel. I'll attach both sets of data to this message. I think the first couple of runs with MEFIscna, I was getting some errors so you see the data jump around a bunch, but the last 2 or 3 were pretty clean. Behavior was the same in all in any case.

    The one thing different today was I put on a 21 pitch stainless prop I had to see if it made any difference. The aluminum prop paint was not in the best shape so I wanted to see if a nice smooth prop made any difference. The only difference is that the motor maxed out 200-250 RPM slower than it did with the 19 pitch aluminum prop.

    I am hoping that something sticks out in this data that points to something I should check or look at. These runs were with just me and my wife (~450 pounds total), half a tank of gas (20-25 gallons), 6-8 gallons of water in the fresh water tank, maybe 150 pounds of other gear, and the 3400 pound boat. We had two other people on it last weekend that added maybe another 250 pounds and it was a struggle to get it on plane when they were in the back. I just remember this boat performing much better in 2017 after I put the motor in it. I followed the recommended break-in procedure for a new motor and babied it until 20 hours. After that, we had 10 people on it and pulled a tube with no problem. Now I am afraid to try and pull a tube. It starts fine, sounds fine, just seems to run out of steam.

    Before I put the motor in, I found low fuel pressure and found out the fuel pump had all the inside paint eaten away (typical Vovlo issue) so I rebuilt it and replaced the pumps. The paint had gotten stuck in the fuel regulator and I got it all cleaned out. Fuel pressure was right on target at 60psi after that. I have not checked fuel pressure this year and the old (treated) gas in it is gone now and I have run quite a bit of fresh 89 octane in it.

    My next steps are to check the compression and fuel pressure again. I'll need to borrow those tools. Any other items to check? Sorry for the long post, just wanted to give as much detail and background as possible. Any help would be appreciated.

    Thanks!!
    Attached Files

  • #2
    I have not checked fuel pressure this year and the old (treated) gas in it is gone now and I have run quite a bit of fresh 89 octane in it.
    Ayuh,..... Examine the Contents of the fuel filter, for anything but clean fresh gasoline,......

    Then replace it, 'n try a run,....

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    • #3
      Before I put the motor in, I found low fuel pressure and found out the fuel pump had all the inside paint eaten away (typical Vovlo issue) so I rebuilt it and replaced the pumps. The paint had gotten stuck in the fuel regulator and I got it all cleaned out. Fuel pressure was right on target at 60psi after that. I have not checked fuel pressure this year and the old (treated) gas in it is gone now and I have run quite a bit of fresh 89 octane in it.
      The motor is running good but unable to reach max rpm is my take away. If correct, find a marine fuel injector place to clean and flow test. Make sure they can test up to 6000 rpms.

      Before that, I would do a compression test
      94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
      95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
      07 Seadoo GTX
      Merc Adults Only VP Adults Only
      G-Dad always said "First Liar doesn't stand a chance"

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      • #4
        Originally posted by Bondo View Post

        Ayuh,..... Examine the Contents of the fuel filter, for anything but clean fresh gasoline,......

        Then replace it, 'n try a run,....
        I did empty the one on the boat now. It looked clean, but I did order a new one a couple days ago just to eliminate it. It should it will be in this week.

        Thanks!

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        • #5
          When was the diz cap last changed ?

          Comment


          • #6
            Originally posted by QBhoy View Post
            When was the diz cap last changed ?
            Not sure. The engine has about 190 total hours on it. I have put ~30 of those on it. I'll take a look at it and order one if it warrants.

            I really hadn't thought about that with everything being electronic, but good idea. Thanks!!

            Comment


            • #7
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              Originally posted by lonewolf41 View Post

              Not sure. The engine has about 190 total hours on it. I have put ~30 of those on it. I'll take a look at it and order one if it warrants.

              I really hadn't thought about that with everything being electronic, but good idea. Thanks!!
              If it’s the crab looking flat cap. They are so well known for failing randomly. I’ve been through 5 in 5 years. They are terrible.

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