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  • temp alarm

    this morning took the boat out to shad fish and after running about 5 min @4200rpm the temp alarm went off. idled back to around 1200 rpm.no problems at that speed for about 10 minutes. tried 4200rpm again and after 5 min alarm went off again. idled back to 1200 and called it a day. water pump seemd fine, engine sounded great both at high speed and low. any thoughts? 1990 115 yamaha 2 stroke oil injected. air temp around 35, water temp low 60's. fresh water. first time boat has been run in around 9 weeks. been in the garage the whole time.
    91 17 standard[br]mt pleasant sc[br]115 yamaha[br]got mako?[br]

  • #2
    there is a small seal under the water pump it looks like a top hat-that seal is probably disrupting the water flow at a higher rpm-so... pull the lower unit replace the water pump{use only yahama oem parts}thermostats if they are more than 3yrs old and replace that seal you should be set for the season!!!

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    • #3
      thank you very much for the info. i am afraid though if i was to remove the lower unit it would stay that way. so my friend the mechanically gifted will help me tomorrow with starting the replacement.
      91 17 standard[br]mt pleasant sc[br]115 yamaha[br]got mako?[br]

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      • #4
        I also have a 171 with a (tired) 1990 115HP Yamaha doing he same time - its used in salt water and doesn't get fresh water flushed. I also suspect the thermosats need changing. Besides the seal mentioned above does anyone have any other suggestions that I should check?
        Steve 171 Mako[br]Jupiter, FL.

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        • #5
          It sounds like your poppet valve (presure relief valve) is stuck closed. At higher speeds most of the water is moved through the engine from the presure at the water pick ups. If the poppet valve doesn't open, the high presure water is closed off from the system. At the same time, the impellor loses effeciency at high engine speeds. If your poppet valve is stuck open, the engine will overheat at idle (impellor water pressure will dump though the open valve.)

          You should be able to order a kit from your dealer. Pretty easy job.
          Tampa, FL [br]Mako 20C Merc 200[br]

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          • #6
            Thanks Tom, I'll check it out...
            Steve 171 Mako[br]Jupiter, FL.

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