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My DF50 overheating at idle and low speed story

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  • My DF50 overheating at idle and low speed story


    I bought Evinrude 1999 50 4-stroke last year and i was hurry to change the engine to the boat, and i did not have the gauges at the moment. The end of the summer went pretty nice with "new" engine, only occasional 3000rpm limits usually when i shut down the engine for 15mins or 30min. Also there was an squeaking sound from the mid section on low rpm. I suspected the dry bushing on driveshaft.

    This year i wanted to do the basic maintenance, because i did not had about info on any maintenance jobs. So i bought waterpump repair kit, both fuel filters and installed Suzuki tach with warning lights.
    Changed the gear oil and greased that noisy bushing. Also the telltale plastic parts in the back was missing, so i bought them too.

    On test run i almost immediatly noticed that i lost telltale after driving boat off from the trailer, it had converted to steam engine. After that the temp warning light. After many restarts i did get the engine cooling again and drive to the near island and back no issues, but when i did get close to my marina i lost the telltale in low speed again.

    Took boat off from the lake and start tearing things apart. I did read this forum a lot and find out that there is lots and lots of potential issues, and basically i just try to rule them all out. I havent had any issues ever with muffs, so i got some kind of feeling that this had to do something with the water pressure. With lower unit in the bucket i did spin the shaft with an drill and i noticed that there are not much water coming from the pump (which has all the new parts, exept for the metallic pump case) Also the pressure was really limited, i could plug the output with an finger without getting sprayed all over.
    Then i noticed that the driveshaft seal was leaking the water out from top of the pump case. Thought that was the issue.

    When i was waiting the seal i did check engine side best i could, probably the best test was to attach hose to the pipe going to pressure valve case and oil pan, with really really small pressure i could verify that engine is cooling like it should, the thermostat opened etc. and pressure valve did not leak.

    When i got the new seal i tested again with an drill and water pressure did seem better, but not great. I installed lower unit back, and this time fill the bucket with water and start testing. This time the results were most confusing, cooling worked 80% of the time well, but maybe with half warm engine the telltale lost and converted to steam. I could feel with my hand that there was no water coming out from the thermostat. After few days i did remove the lower unit again, and checked the water pump for the maybe 10th? time, and then i did see whats wrong.

    The plate was different, the hole was later on clockwise direction that in the plate i had installed before my waterpump rebuild. Shame that i did not take the picture, but here is a pic from service manual where i have drawn the hole position in wrong part with yellow.

    Othervise the plate did fit perfectly and never came in to my mind that it could be different, also the seal under the plate was spot on and the impeller itself. The repair kit was aftermarket, and now when i think i should have been more careful with it, because it had the metallic cup and the seal for the plastic pump case, i just thought that the same repair kit fits to other models too. Next time i will verify the parts before installing, or just use genuine parts.

    After switching back to worn plate i tested with drill and instantly did notice the pressure and water flow increase on pump. Installed the lower unit again and did run the engine this time on muffs with low pressure from the hose, no lights, cool engine.

    Took the boat to the lake and had "only" minor issues that the tell tale started to dribble when engine idled long time, but this time it came back strong when i raised the engine speed even a little. That may be caused from that worn plate with pretty deep groves on it.

    Hope this all helps someone someday!

  • #2
    Don't know if yours is the same as a suzuki df 50 but I'll ask anyway. The manual says to drop the lower unit you must separate the clutch rod from the shift rod. Was this difficult when dropping or reinstalling? any tips as I need to change out the impeller. thanks


    • #3
      Hi, its pretty simple. You can separate them with 2 10mm wrenches, just try to keep smaller locking nut in pretty much same position, when you reinstall you know how much to turn the turnbuckle nut back.

      Last tip is to check out that the new water pump plate looks like the old one.


      • #4
        I always take pictures of any linkage I take apart so I can count threads when reassembling.