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Merc 4.3L MPI Overheated on Driveway

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  • #16
    I'm with AD. No way I'm lifting the lower up to reinstall.

    And wow - been like forever since I had a pretty new looking outdrive like that!
    17 Foot '90 Bluewater
    Alpha 1 3.0 Merc - repowered in 2016
    now - 4.3L Vortec - Alpha 1 GenII
    Honda BF100L kicker
    Engine custom - Transom 0D65328 - Drive 0D648864
    If you ain't fishin, then yer working too much.

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    • #17
      Got it on! That's wasn't fun.
      What should I look out for when I take her out for any errors in my re-install? Biggest one I've read is it stays in neutral?

      PS- Thanks for all the help. Couldn't have done this without you guys

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      • #18
        You should be good if you fired it up and have water coming out the exhaust and not pouring out between the halves
        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"

        Comment


        • #19
          Originally posted by alldodge View Post
          You should be good if you fired it up and have water coming out the exhaust and not pouring out between the halves
          Too scared to fire it up on the driveway now πŸ™„... I'll take her to the lake down the road and test it out I guess.

          Comment


          • #20
            Originally posted by Rick Stephens View Post
            I'm with AD. No way I'm lifting the lower up to reinstall.
            I thought I was weakling wimp back about 4 years for struggling to get my Gen 2 lower on from an impeller change.

            If I had issues with spline alignment, I just put it back on my DIY stand and used the prop while the lower was in forward gear to make small adjustments.

            The first bolt/nut is the hardest so that the weight is supported. After that, it's all gravy.

            Sirvoc2, did you check verify the old lube did not have water intrusion?

            Did you verify that the lube hole o-ring between the upper and lower was properly in place and not damaged or warped? That is a part included when you get the impeller assembly kit, not just the impeller.

            With the drive as level/down as possible, did you fill high performance gear lube from the bottom hole until it comes out of the top vent hole, close the vent hole, then unscrew the lube reservoir monitor and keep filling until it reaches the fill line?

            Did you do a basic water pump check with muffs on a hose that supplies sufficient water pressure? You should at least be able to reach and maintain safe operating temperature on the engine and manifolds and hold that for 700 rpm idle.

            Any further tests would need to be made on the water under load or with a dyno that supplies high enough water flow/pressure.

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            • #21
              I never go to the lake without first checking things on muffs. There is no way to know if the impeller is pumping water until your engine gets hot enough to smoke when you are lake testing. You need to get over the fears and do the testing right. Fire up water, fire up engine, stand in back and watch for water out the bypass holes. Take the drive in and out of forward and reverse. Watch the motor come up to temp and stay there. THEN, go boating.
              17 Foot '90 Bluewater
              Alpha 1 3.0 Merc - repowered in 2016
              now - 4.3L Vortec - Alpha 1 GenII
              Honda BF100L kicker
              Engine custom - Transom 0D65328 - Drive 0D648864
              If you ain't fishin, then yer working too much.

              Comment


              • #22
                Maybe a dumb question. Do i top up the gear lube tank inside the motor compartment after I pump it in from the bottom drive?
                i assume yes as the tank was full before but now is empty?

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                • #23
                  Originally posted by Rick Stephens View Post
                  I never go to the lake without first checking things on muffs. There is no way to know if the impeller is pumping water until your engine gets hot enough to smoke when you are lake testing. You need to get over the fears and do the testing right. Fire up water, fire up engine, stand in back and watch for water out the bypass holes. Take the drive in and out of forward and reverse. Watch the motor come up to temp and stay there. THEN, go boating.
                  Fair points for sure. I'm going to go buy new muffs and give it a go. My current set is really old

                  What is ideal operating temp?
                  Assume if it shoots over that shut her down ASAP even if alarm hasn't gone off?

                  Comment


                  • #24
                    Originally posted by Sirovc2 View Post
                    Maybe a dumb question. Do i top up the gear lube tank inside the motor compartment after I pump it in from the bottom drive?
                    i assume yes as the tank was full before but now is empty?
                    Yes, without the upper removed the bottle will slowly drain out.

                    You did pump the lube in from the bottom to top, right?
                    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"

                    Comment


                    • #25
                      With open cooling the cooling system has no pressure. Bubbles form in water on surfaces inside the motor between 170 and 180Ζ’ (depending on altitude). Those bubbles prevent efficient transfer of heat from the metal to the water. Best temperatures with open cooling is under 170, I run mine at 150 since everything I run at is over 2000 ft ASL..

                      Safe operating temperature is higher as the motor is designed to run over 200 with a pressurized cooling system. As well, antifreeze raises the boiling temperature of water. And the fuel burns more efficient up there as well. Another reason to own closed cooling :^) But once you get up over 190Ζ’ the plain water in the cooling system will be boiling in places, causing bubbles and steam and preventing efficient cooling.

                      I don't have an alarm on my older boat. I would hope to be paying attention and see if idling, or running at a little higher rpm would resolve the overheat. For me, if I see over 170 I am going to sit up and take notice, but I'm not going to shutdown until I take a couple minutes to figure it out. If possible. On the water, possible reasons to overheat are many, most common is picking up something like a plastic bag that covers the intake ports.
                      17 Foot '90 Bluewater
                      Alpha 1 3.0 Merc - repowered in 2016
                      now - 4.3L Vortec - Alpha 1 GenII
                      Honda BF100L kicker
                      Engine custom - Transom 0D65328 - Drive 0D648864
                      If you ain't fishin, then yer working too much.

                      Comment


                      • #26
                        Originally posted by alldodge View Post

                        Yes, without the upper removed the bottle will slowly drain out.

                        You did pump the lube in from the bottom to top, right?
                        Yes I did πŸ‘

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                        • #27
                          New muffs, ran water, fired her up and looks good to me. Good water flow, forward works, reverse works. Ran for 7 mins and temp gauge barely moved. Think I'm good to go?
                          Have a peak at the video if anyone doesn't mind....

                          https://youtu.be/kD2qDXQHths

                          Many thanks again.

                          ​​​​

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                          • #28
                            Don't run the engine with the drive trimmed up like that. Stresses the uni joints (yes, even in neutral!)

                            Chris.............
                            xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
                            The world takes on a whole new perspective when viewed from 100’ below.
                            1972 Bertram β€˜Bahia Mar’ 20
                            2006 Mercruiser 4.3MPI (0W617679) w/Alpha One Gen II (0W829301)
                            (Original - 1972 '165' In-line 6. Previous - 1994 4.3LX)


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                            • #29
                              Sign up today
                              Go boating!
                              17 Foot '90 Bluewater
                              Alpha 1 3.0 Merc - repowered in 2016
                              now - 4.3L Vortec - Alpha 1 GenII
                              Honda BF100L kicker
                              Engine custom - Transom 0D65328 - Drive 0D648864
                              If you ain't fishin, then yer working too much.

                              Comment

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