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  1. M

    rough running at all RPMs

    Just launched for the season. Too many rainy weekends. 1988 Three cylinder 50 HP Mariner. The engine starts right away, idles normally. Fresh fuel and correct oil mix. But no power. It feels like its not making full RPMs and sounds rough but not like its running on two cylinders. I know ignition...
  2. M

    Mariner 50HP overheat alarm

    I get a HighTemp alarm only at WOT. New water pump. Lot's of water in the telltale stream. I opened the head and exhaust covers and water passages are clean. However there is no thermostat installed in the engine. Should there be one? Its a 1988 Mariner 50 HP 3cyl. S/N OB248535. Could no...
  3. M

    Can brands of Oil effect temp alarm?

    My Mariner 50 HP 3 cyc. on a 15 foot Whaler has a high temp alarm problem only at WOT. I have tried all of the ususal stuff, water pump, etc, no luck. My wife ran the boat today and switch fuel tanks to the backup tank that had been filled with with an unknown mixture from the old owners marina...
  4. M

    Mariner 50 HP overheat alarm

    My 1986 Mariner 50 sounds the temp alarm only at WOT. Replaced the water pump and have good telltale water flow before and after the replacement. Temp sensor seems OK based on a stove top test. Does anyone know if this engine has a thermostat? The manual is not clear about this. It is a 3...
  5. M

    1986 Mariner 50 HP overheats @ high RPM

    My 1986 Mariner 50, 3 cylinder, sounds the temperture alarm (Steady Buzzer)whenever operating the boat at high speed. The alarm goes off as soon as I back off the RPMs to mid range or idle. Good water flow from the telltale at all RPMs. Rebuilt the water pump and tested the temp sensor in...
  6. M

    water system flush

    Is there a product that can be safely used to flush an outboard's water jackets. Something stronger than fresh water but not as agressive as automotive radiator flush. I'm having a high temp problem under heavy load and the water pump is new. I'm thinking that salt buildup could be reducing the...
  7. M

    Mariner 50 overheats at high RPM

    My 1986 Mariner 50, 3 cylinder, sounds the temperture alarm (Steady Buzzer)whenever operating the boat at high speed. The alarm goes off as soon as I back off the RPMs to mid range or idle. Good water flow from the telltale at all RPMs. Rebuilt the water pump and electrically tested the temp...
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