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    Mercruiser 350 engine life advice

    I am interested in buying a boat with Mercruiser 350 MAG mpi., ran for 300h, good service history. the engine is 10 years old (2008 model) however i dont have previous experience with Sterndrive engines.
    I have requested Mercury to run inspection and computer diagnostics for engine health check.

    Is 10 years old engine a bit too old for an engine? whats the expected life span of such engines ? when would an engine become too old and require replacement? any other tips would be appreciated
    cheers

    #2
    300 hrs is low for an engine that is 10 yrs old. Heck I put that in one season .
    while those hours can give you a good base line... all depends on how she was maintained and what kind of RPM range this thing ran. How much fuel went thru that engine is more important than its hours.
    don't trust that engine hour meter ... see if you can find a dealer with a Rinda Mercruiser scan tool to be certain.
    a good properly maintained marine gas engine shouldn't have any problems up to 2000 hours or more.
    many boating yrs left on that engine, especially if you are only putting 30 hrs annually LoL
    Joon, Kathy, Jaden & Tristan
    Uniflite 42 AC, DD 671N
    93 3058 sold
    92 2855 (day boat)
    91 Fourwinns 205 (lake boat)
    Longbranch WA
    Life is Good

    Comment


    • Modi
      Modi commented
      Editing a comment
      Many thanks
      I have booked it with Mercury to do CDS the computer disgnostic test and some other inspections by their mechanics . this is all the test they can do in Dubai
      Is it possible to tamper with the hours meter ? if yes , is there a way to tell?

    #3
    Anytime & welcome to the club!
    anybody can tamper an hour meter easily & nope no way you can tell.
    get it scanned,
    perform a compression test,
    sea trial is a must, ensure she will reach her recommended WOT... propped properly ,
    send in her oil sample to be analyzed .
    Joon, Kathy, Jaden & Tristan
    Uniflite 42 AC, DD 671N
    93 3058 sold
    92 2855 (day boat)
    91 Fourwinns 205 (lake boat)
    Longbranch WA
    Life is Good

    Comment


      #4
      My 1987 305's are original and running fine. The low hours make the maintenance that much more important.

      Comment


        #5
        Originally posted by Modi View Post
        I am interested in buying a boat with Mercruiser 350 MAG mpi., ran for 300h, good service history. the engine is 10 years old (2008 model) however i dont have previous experience with Sterndrive engines.
        I have requested Mercury to run inspection and computer diagnostics for engine health check.

        Is 10 years old engine a bit too old for an engine? whats the expected life span of such engines ? when would an engine become too old and require replacement? any other tips would be appreciated
        cheers
        You will see three types of cooling systems:
        .....Raw Water Cooled
        .....Half Closed Cooling System (exhaust manifolds not included)
        .....Full Closed Cooling System (exhaust manifolds included)

        If ten years old and Raw Water Cooled, and if operated in Ocean water, I would be concerned..... even at only 300 hours!


        .

        Rick E. Gresham, Oregon
        2850 Bounty Sedan Flybridge model
        Twin 280 HP 5.7's w/ Closed Cooling
        Volvo Penta DuoProp Drives
        Kohler 4 CZ Gen Set

        Comment


        • Modi
          Modi commented
          Editing a comment
          many thanks
          it is raw water cooled
          Mercruiser did full inspection and CDS test
          they commented that cooling system is running cold at 140F instead of 150-170F is that a problem?
          they also reported that block water sensor needs replacement - no reading
          any advices?

        #6
        That cold running could be nothing more than a thermostat that does not close all the way (common in open cooling systems due to rust flakes and sand/grit getting stuck in the thermostat, keeping it open a bit.
        HOWEVER....raw water cooled....if in SALT water....the exhaust system needs regular maintenance checks at 5 years, and may well need to be replaced at 5-7 years, due to salt water corrosion. If this was done, then fine the engine could have a lot of life left in it but if not, there is the risk of salt water leaking inside defective exhaust manifolds or elbows and getting into cylinders via an open exhaust valve. This causes corrosion of exhaust valves and can in extreme situations cause cyl wall rusting.
        Was the engine used in salt or fresh? Its a big difference in the possible problems you can face.
        I would make sure you do a good water test and make sure that it reaches it's specified max rpm, pulls the load of the boat well, the outdrive shifts properly, does not jump out of gear, make odd noises, etc. Check the bilge and transom mount area carefully for leaks.

        I still think you'd be better off by far with an outboard boat, with an engine that is supported in your location. Take it from someone who owns a boat with a drive system most mechanics won't work on (OMC Cobra). It has been very good to me with minimal problems but out of production for a long time. Most mechanics here only work on Mercruiser and newer Volvo. Anything else and you have to search around for someone or do it yourself.
        88 Four Winns 200 Horizon 4.3 OMC
        98 Jeep Grand Cherokee 4.0/Selectrac
        07 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

        Long Island Sound Region

        Comment


        • Modi
          Modi commented
          Editing a comment
          much appreciated, thank you
          you are right , they said the thermostat is not working

          it was run in salt water , water salinity is a bit higher than ocean water.
          the computer diagnostics was done ,
          reported WOT 3400 rpm. i think thats low for this engine
          compression test was between 170-185
          oil pressure 507psi at idle

        #7
        low WOT is a concern, Should be more like 4400-4600. Compression test results are OK. Oil pressure @ idle (think you meant 57?) is usually 40 cold engine but can drop to about 20 with a hot engine, that's still OK.
        Concern is the salt water use and as I mentioned was the exhaust system maintained. Good comp test results suggests it probably was. But, after 10 years in very salty water I can tell you this:
        I took apart a 4.3 used in moderately salty water for 15 years. The block was fine but the cyl head cooling passages were getting eroded to the point where the machine shop guys felt it was better to install re-man heads than to rebuild these. So you might get 5 more good years if careful. If it was closed cooled I would not be so concerned. However the same holds true for outboards, they get a good 10-15 years in very salty water and after that, on borrowed time.
        88 Four Winns 200 Horizon 4.3 OMC
        98 Jeep Grand Cherokee 4.0/Selectrac
        07 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

        Long Island Sound Region

        Comment


          #8
          Mercruiser 350 Mag should be turning 5000 RPM @WOT... so she's been running over propped & that engine has been lugging, who knows how long.
          it is extremely critical that your engine is able to reach within the recommend RPM range at WOT.
          ECM stored scanned total hours?
          Joon, Kathy, Jaden & Tristan
          Uniflite 42 AC, DD 671N
          93 3058 sold
          92 2855 (day boat)
          91 Fourwinns 205 (lake boat)
          Longbranch WA
          Life is Good

          Comment


            #9
            Seems I recall the recommended thermostat temp rating for saltwater use is 140 and freshwater use is 160. Don't take this as gospel, but I believe the 140 temp in salt is because saltwater will crystalize at higher temps.

            You may research that issue.

            The WOT RPM is off as mentioned....it may be sure to incorrect prop as mentioned.
            2008 H210SS Four Winns
            Volvo Penta 5.7 GISX
            Prior: 1997 2050SS Bayliner
            Brad / Texas Gulf Coast

            Comment


              #10
              What size boat, large cruiser?
              As stated the 3400 WOT rpm is super low.
              You sure that wasn’t the “cruising” rpm?
              Was there marine growth on the hull bottom, outdrive or prop?
              Dave
              Edmonds, WA
              "THE FIX"
              '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
              (.030 over-Vortec top end-part closed cooled)
              The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
              Misc. projects thread
              https://www.baylinerownersclub.org/f...56-gctid789773

              Comment


                #11
                the boat is bayliner 245, 24ft , Mercruiser are the ones who did the computer diagnostics test and inspection
                They said the temp should be is 150-170 F
                I have asked them to confirm if the 3400 rpm is really the WOT or cruising rpm as it is quite low.
                the belows and the drive were not inspected as the boat is wet berthed in the marina
                but the boat had polish work done 6 months ago with anti fouling and the usual service.
                with this in mind and the fact that there is no much support for Mercruiser inboard engine support , i am worried i will get in trouble with it

                Comment


                  #12
                  Agreed. A 10 year old Mercruiser in salt water with unknown service history and no local support, spells trouble to me.
                  88 Four Winns 200 Horizon 4.3 OMC
                  98 Jeep Grand Cherokee 4.0/Selectrac
                  07 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

                  Long Island Sound Region

                  Comment


                    #13
                    many thanks
                    it is raw water cooled
                    Mercruiser did full inspection and CDS test
                    they commented that cooling system is running cold at 140F instead of 150-170F is that a problem?
                    they also reported that block water sensor needs replacement - no reading
                    any advices?
                    I know of no way to ensure that the inside of the cylinder block has not become compromised due to Raw Water cooling for this long.
                    Also, operating at 140* is OK for running in Ocean water, it is too cold for running in River/Lake water.





                    much appreciated, thank you
                    you are right , they said the thermostat is not working

                    it was run in salt water , water salinity is a bit higher than ocean water.

                    All the more reason for walking away...... Or, for planning on a new engine in the not so distant future!

                    the computer diagnostics was done ,
                    reported WOT 3400 rpm. i think thats low for this engine
                    If that is a true and accurate WOT RPM test, this engine has been "Over-Burdened" for who knows how long!!!!

                    compression test was between 170-185
                    I would want to verify this myself!

                    oil pressure 507psi at idle
                    Must be Typ-O.
                    If 50 psi, that is excessive for idle RPM.



                    Rick E. Gresham, Oregon
                    2850 Bounty Sedan Flybridge model
                    Twin 280 HP 5.7's w/ Closed Cooling
                    Volvo Penta DuoProp Drives
                    Kohler 4 CZ Gen Set

                    Comment


                      #14
                      Originally posted by Ruffryder View Post
                      Anytime & welcome to the club!
                      anybody can tamper an hour meter easily & nope no way you can tell.
                      get it scanned,
                      perform a compression test,
                      sea trial is a must, ensure she will reach her recommended WOT... propped properly ,
                      send in her oil sample to be analyzed .
                      This guy is right on the money ^

                      An hour meter means absolutely nothing! Age also means practically nothing as long it has closed cooling. The unfortunate thing about boats is that people can abuse their engines with poor maintenance or run at WOT all the time, and sometimes you'd never know it after only a few hundred hours.
                      1995 Bayliner 2452 Mercruiser 5.7L Alpha 1 Gen 2

                      Comment

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