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Mercruiser 228 got hot, but was it too hot?

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  • Mercruiser 228 got hot, but was it too hot?

    cruisin through my harbor, for a good 15 mins before heading out into long island sound, all gauges were good, cruised across the sound probably about a 1-3 minute ride , pulled back on throttle was cruising just a little off plane for maybe 2 min, looked down and my temp was super high, I'd say 220 tops. So I shut everything down, opened the hatch and let her cool, both exhaust manifolds were hot, the coolant tubes on the top of the engine were hot, although I could touch them I couldnt hold my hand on them for long. Nothing smoked or smelled funky. Waited til she cooled to 160, started right up, starting cruising at 5-10mph and temp went back to normal 140, heading back in the whole time doing 10mph tops and engine ran fine, sounded fine, and temp stayed a consistent 138-140. I know I have to go check some things out because something isn't correct, but do you guys think I've done any damage and where should I start to diagnose? Any help would be greatly appreciated

    Thanks guys

  • #2
    Forgot to mention, engine is a mercruiser 228, chevy 305 small block, with a 2 barrel carb, raw water cooled, alpha 1


    • #3
      I don't think 220 would hurt it esp since you caught it fast. What I'd do is check the exhaust hoses and flappers, and then maybe do a compression test. Check the oil for water. Probably fine, you may have picked up something on the lower unit. Might want to check your raw water flow with the boat in the water. How old is the exhaust system? In the region you boat in (LI Sound) raw water cooled exhaust should be replaced every 5-7 years to be on the safe side. When the risers get clogged up you can have high temps like that.
      1988 Four Winns 200 Horizon
      4.3 OMC Cobra

      98 Jeep Grand Cherokee 4.0 Selectrac
      07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

      "While air doesn't freeze....rust never sleeps"


      • #4
        Tough one. Depending on what caused the overheat will direct you in the remedial work. But it looks like you don't know... If it was a plastic bag on the water intakes, then you need to check the water pump impeller, housing and base, water pocket cover, exhaust shutters and all the rubber in the exhaust path. If it was debris caught in the thermostat, then just pull the thermostat and clear that. As water would still have been flowing through the system, all those other things will have been fine.

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


        • #5
          Thanks guys for your support, the exhaust manifolds and risers were done within the last 2 years, I'm going to head down to the boat in about an hour to see if I can figure anything out, again thank you


          • #6
            if it got hot, there was no water flow. your flappers are most likely burnt along with your rubber exhaust hose (rated at 250F)

            you may or may not have done further damage, however like Chris says, pull the drive and get to the impeller. while your in there, I would simply change the impeller and raw water pump.
            1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - http://forums.iboats.com/forum/owner...988-rogue-2420

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

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


            • #7
              if you do the impeller, u can find the hose coming from the transom tot he front water pump, and see how long it takes to fill a bucket.. however since it rn fine at 140 afterwards it it a bit odd.. perhaps a plastic bag wrapped around the water intake, but that is so rare!

              You might have a small crack in the water hose coming up form the outdrive which might still supply water ..

              Bit of a hack way but this might give an indication:
              When u remove the lower leg to do the impeller.. plug the copper water pipe going up into the upper (make sure its in and seated) and block it with a rubber stopper. Find the hose that comes from transom to water pump in front of motor (usually about 1-1/2 or 1-3/4"), remove it and fill with water.. see if the level goes down. if so u have a water leak somewhere between the motor and the outdrive (bad).

              Obviously the pump puts out more pressure than just gravity but it might show u something. Tilt the drive up and down a little - this will flex the water hose and possibly reveal a leak..


              • #8
                Hey guys thanks for all the support, I went down and checked everything out I could without pulling the drive, everything seemed fine, so I raised the out drive, and cleaned the lower unit where the water inlet is, there wasnt anything major blocking the inlet or anything but i figured why not. Since then I've taken the boat out 4 or 5 times without a problem. Temps are always on point and boat runs great.

                I know I should pull the drive and check the impeller but the boat is coming out of the water in the next week or so, and I plan on doing alot of upgrades and repairs to her then. I think I may have just had something like sea weed or the very very rare situation of picking up a bag, although in long island sound you never know what you're going to come across.

                Again thank you guys for the support I greatly appreciate it!


                • #9
                  Is the boat docked or moored in salt water? If so there is a chance you had some barnacles growing up above the water intakes in the water passage. I have had this problem and have split the drive a couple of times to clean them out. While the boat is still in the water, why not do a raw water pump output test, that will tell you for sure without taking anything apart.
                  1988 Four Winns 200 Horizon
                  4.3 OMC Cobra

                  98 Jeep Grand Cherokee 4.0 Selectrac
                  07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

                  "While air doesn't freeze....rust never sleeps"


                  • #10
                    Hey guys. So it's back to getting hot while on plane, the boat is docked in salt water, how do I do the raw water pump test? Also what other tests can I do to rule other things out? I can idle and cruise around my harbor without any issues, once I get underway say above 15-20mph, temp starts to creep up, once she gets around 180, I back off to a stop then start cruising slow again, and the temp comes right back down to normal temp


                    • #11
                      Sounds similar to what I just went through - same symptoms. For me, it was bits of impeller clogging the water intake tube, so engine was not getting adequate flow. for what it's worth, I could not simulate this condition on the hose; only on water. Once the impeller pieces were removed, the problem was solved. I was told that flow from the stern drive to the thermostat housing (when hose is removed) should bubble out of the hose 5 inches. However, I am not certain at what RPM that occurs.


                      • #12
                        So what did you do remove the house from the stern drive to the thermostat at the thermostat? And flush water in through muffs on the outdrive? To remove all pieces? Or what would I have to do to see if that inlet house is clogged?


                        • #13
                          Overheat at speed can be a symptom of clogged exhaust manifolds or risers, especially so in salt water.


                          • #14
                            The manifolds and risers were done in the past 2 years, but i think im going to have to do them again if that's the case, should I upgrade to the newer ones with the riser in the center or find old style one's with the riser on the back of it ?


                            • #15
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                              It is far more likely that you have a low raw water flow into the cooling system, than clogged risers because they are only 2 years old. Usually you don't start to see clogging there till about 5 years. I would look up the spec Merc uses to measure raw water flow, and do that test with the boat in the water. If its low then its time to remove the drive and do the impeller, plus look at all the places where old impeller bits can get lodged (transom water hose, thermostat housing, manifold and riser feed hoses). When replacing the impeller, check the water intakes for marine growth. This is a problem I had till I removed that screen that OMC put in the lower units on the Cobra drives, barnacles would grow right on it. I made a clean out tool out of stiff wire and I can rod out the water intake holes and the area just above it even with the boat on the mooring by tilting the drive all the way up. If its never been cleaned out, or not in the last 3 seasons or so, you'd be surprised what can grow in there. I boat in the same region as you do (Long Island side of LI Sound) and this is a common problem. My mechanic says the clean out should be done about every 3 seasons if the boat is moored or docked in salt water. My temps were getting close to 185 before I cleaned it out and after that, it went back down to its usual 160.
                              Last edited by Lou C; October 2nd, 2017, 04:47 PM.
                              1988 Four Winns 200 Horizon
                              4.3 OMC Cobra

                              98 Jeep Grand Cherokee 4.0 Selectrac
                              07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

                              "While air doesn't freeze....rust never sleeps"