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Yamaha 150 lost power

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  • Yamaha 150 lost power

    I have a Yamaha 150 FETO model year 2001 and similar to the US model 150 TXRZ, 2.6 litre carbed V6. It is a new to me engine and during the winter I plan to service the carbs, fuel pumps, thermostats, pressure control valve, sync and link and all filters. Parts are on order but have not arrived yet.

    Last trip I noticed a slight power loss, WOT was 5200 rpm and 48 mph compared to 5700 rpm and 54 mph. Also hole shot was affected. Otherwise the engine runs good. Tested compression which was 105 - 115 psi, same as tested when i bought the boat. Renewed the spark plugs but the loss of power is still there. Plugs were worn but color was ok, cylinder 1 just a small bit darker than the others.

    I also noticed that both cylinder banks runs too cool and that water temp here has fallen rapidly since last trip. The thermostats is obviusly bad. The engine has a temp sensor on the starboard cylinder bank. Anyone knows exactly what this sensor does? I know it plays a role at cold start but does it affect the timing also at higher revs? To me it feels a bit like that the ignition is not fully advanced.

  • #2
    Engine back at 5700 rpm and 54 mph. The culprit was a bad ignition coil on cylinder 5, starboard lower. Still interested if the ECU alters the ignition timing other than at cold starts..?


    • #3
      No ECU on that model. A CDI assembly is used.

      Electronic timing for starting and cold engine warm up. Mechanical timing for normal operation.
      Last edited by boscoe99; 10-23-2021, 11:54 AM.