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Engine temp. rising higher than half when planed out...

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  • Engine temp. rising higher than half when planed out...

    Last Sunday, had the engine temp. warning go off on me. Thought the intake was blocked, nope. Able to bring the temp. down to half way point if I backed off of throttle. Yesterday was able to get back down there and I put a new impeller and seal in on the seawater pump. 3 things the local boat mechanic told me-
    1) check temp. sensor - can't be this, since I am getting linear movement when temp. rises when I was planed out, and then drops when I ease off throttle.
    2) check impeller and replace if necessary - this is what I did yesterday (see pic of old one before I removed).
    3) flush out oil cooler water intake, sometimes sand/muck can build up in this and cause engine temps to rise 10-15 degrees - this will be my next task when I get back down there. Usually I use the muffs on outboard before the season starts, but this time I did not... wondering if this could've also lead to the higher temps since when I normally perform this I get some sand/dirt to come out.

    I also attached a picture of the dash gauges when planed out (disregard trim gauge as this is not working) and photos of the oil cooler which is located on the top/aft of engine. The yellow circles are the water hoses. Question - which to remove to flush out with garden hose or should I just use the muffs on outboard and call it a day?

    Any other insight would be appreciated, cheers boaters!

    Attached Files

  • #2
    Kinda sucks that your temp gauge doesn't read out with the actual temperatures. How high was your gauge reading? (relatively speaking..).

    If I understand correctly, you're saying that when you're running and sustaining higher RPM to be on plane the overheat occurs, otherwise when in idle, it's fine?


    • #3
      Typed up initial post rather quickly.

      Alright, so before I replaced the impeller (which from looks of picture and when I took it out, should little signs of deformation), that is when the temp. hit red line and I got the audible warning along with telltale on dash.

      After replacing impeller, gave it a test run, and temp. never redlined.... went no higher than the dashboard gauges photo I posted. I want to say before the overheat occurred on Sunday, my average temp. was right around the middle of the gauge ~50%.

      And yes... this is the old VDO dash :/


      • #4
        Might want to remove the thermostat and test it in a pot of water on the Admiral's kitchen range. Use an old pot!
        Please, no PM's (Private Messages) regarding boat/engine problems.
        That is what the forums are for.
        Only forum/moderator issues will be answered in PM's.


        • #5
          ^ Yeah, I guess those old VDO dashes were pretty basic. So, from what your saying, the overheat is not occurring now that you've replaced the impeller? Had you been running earlier in the year without any trouble? that is, just an isolated event last Sunday?


          • #6
            Overheat did not occur yesterday after I replaced impeller, however it seemed to still be running a little higher than normal. It did appear to be an isolated event on Sunday. The impeller was changed about 4 years ago, so I replaced anyway but like I mentioned, there was little sign of deformation.

            Earlier in the season, seemed to be okay on temperature, and want to say it was right around the half way point on temp. gauge, not the 3/4 like it was running yesterday.

            Aside from using muffs on the outboard to use the pressure from water hose to help clean out any debris... which side of the oil cooler should I remove to also give that a flush?

            Just trying to identify other areas that be be suspect to blockage or any areas that could cause the higher than normal temps.


            • #7
              May be a stupid question but is your impeller missing the woodruff key that spins it?


              • #8
                The impeller does not have a woodruff key in the gearshaft.

                So took boat out today and still saw a tiny drop of water after running for a bit, coming from the front side of pump (not rear housing with the inlet/outlet hoses). Is there another seal in there? It's not that bad of a leak, but would seem to become problematic over time.

                I also gave a squeeze to the outlet hose, which seemed to be fairly spongy and sounded almost as if there was air releasing or being sucked back in. Should both inlet and outlet hoses do this? When squeezing, no water comes out from any area of hose clamp connection points.

                Temperature still seemed to run a little higher than normal.


                • #9
                  Really helps if you tell us what year and model ??
                  It's important because some Volvo's don't have risers?
                  The overheating at higher rpm's
                  That sounds like a riser or the manifolds clogged?
                  Maybe crud in the thermo?
                  Maybe the cam in the pump's worn down and not pushing enough water?

                  Buy American made Cars and Trucks!!!Towing insurance for a boat,a GREAT thing.
                  ​Tools to make my life easier: Battery tester, die grinder, temp.gun, compression tester, DVA meter.

                  In Scenic , Beautiful San Sebastian by the sea Florida

                  88 Bayliner 21CC 2001 Mercury 225 HP EFI



                  • #10
                    7.4gi 454.



                    • #11
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