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Bf150 overheat alarm

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  • Bf150 overheat alarm

    Have a 2004 BF150 (two actually on Glacier Bay 2670. Starboard engine has always had intermittent rough idle and had to use forward throttle position (in neutral) sometimes to start. Once started runs great, never had overheat alarm. Both engines are connected to fuel sensors on Garmin 5212 GPS. Fuel flow is consistent on both.

    Just replaced both thermostats, impeller, sparkplugs, high and low pressure fuel filters, oil and filter, lower case oil…according to factory specs, all parts genuine Honda parts, except plugs, they are NGK , but exact type recommend by Honda and same as what was removed. Total engine hours is 630, all these parts were last changed by previous owner at 520 hours.

    Port engine… same as always---purrr-fect. Starboard however starts ok, but overhead alarm sounds after a few minutes. Using tight set of water ears on lower engine with good water flow. Engine has water exiting from pee-hole---same amount as port engine…so water flow is there.

    Removed lower leg to check impeller and it looks perfect. BTW--- impellers that were replace looked perfect also, and had no issues. But since I had 2 new, cheap insurance I thought.

    Any advice (without having to use a large sledge hammer!!!) would b very much appreciated.

    Many thanks,


  • #2
    Best to put them in water to test, may not be getting enough water with garden hose.
    Honda Outboard Parts


    • #3
      Regarding the BF150 overheat alarm.....

      Reassembled lower leg, immersed in deep can for safe water level, started right up and….

      Ran perfect!! Idled for 10 min, and then advanced to 1500-2000 rpm for short time. Fuel flow was as should be, water check stream (on side case) solid stream.

      Will advise if when placed in service, any issues arise.




      • #4
        Measure the leaving water temperature. Low water flow will show up as higher leaving water temperature. If the leaving water temp is the same between both engines, then start working on the alarm electricals.


        • #5
          I held my hand in the flow, using the flush ears the flow was noticeable less and warmer, with engine immersed in bucket, strong flow and water stayed almost cool even after extended idle and few rev intervals.

          This engine still has slightly rough idle, the port engine is very smooth, so its easy to compare the two side by side. It seems to be set at about 750-825 rpm. Is there an easy way to adjust idle up abit?