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1988 Yamaha 2 stroke Outboard won't idle now.....

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  • 1988 Yamaha 2 stroke Outboard won't idle now.....

    So here's my sob story. First and foremost I can honestly say the best 2 days in a boat owner's life are.....well anyway....

    I grew up on Tuna Boats in San Diego, worked Islandia and Seaforth Sportfishing, fished Point Loma. After my ilIllustrious sport fishing career I mowed lawns and did all my own engine repairs on vehicles and two strokes. I hhave some idea.

    Here's my story. So I bought 22 foot Hulls Inc Bayrunner, 1988, with a 1988 Yamaha 90 hp 2 stroke outboard motor. I bought the boat from a fire man at my church who had just replaced this longtime boat of with a 30 foot dual outboard fiberglass skiff with a flybridge and was tired of debugging the engine he just replaced the juggs on. So we test drove it and after about 10 minutes or so, it would drop into safe mode, unbeknownced to us. So we replaced the fuel filter(s), nothing. Motor ran great,...for ten minutes. We spent a whole day on Lake Elsinore, I believed he rebuilt the motor.

    So he gave me a nice discount and I bought the hull, with a motor that didn't work,......well. After I brought the boat home I replaced all the fuel line and eliminated some extra bubble pumps he had installed in an effort to solve the problem. New Plugs, oil, gas. Boat started right up.

    Still wouldn't run under load for more then 10 minutes without going into safe mode.

    So I became discourage and the boat sat for 3 years. Finally I took it someone who claimed they understood outboards. He spent three months on it during El Nino in 2007. (lol) He had me buy all new coils, (3), I paid for an impeller (which he later refunded) and other electrical cleanup from the prior owner. So I test drove the boat after the Mechanic connected some loose wires and changed the impeller(?). On the first test drive, after about 10 minutes of flawless operation, a buzzer went off and the boat dropped into safe mode. So I explained what a happened to the "outboard" mechanic and he went on to the coils, etc. Every test drive was a repeat, buzzer, safe mode. I had no idea what was happening. Neither did the mechanic who had in-inadvertently re-connected the Heat/Oil sensor/buzzer.

    So with the fishing season gone with the wind, I broke down and drove an hour and a half to a certified Yamaha Mechanic who repaired the problem in thirty minutes. He replaced the impeller, showed me the old cracked bent one, and flushed the coolant system.

    Motor ran flawlessy for 2 years until 09 and then I stored it for two years.

    One thing. The last trip I was on was a freshwater party trip to a lake where I played water taxi. On the lastrip back to the doc it started missing, almost a safe mode incident, but no buzzer.

    I drove the boat last week and it simulated safe mode with no buzzer. I assumed. I had went ahead prior to test driving it changed filters as routine, checked plugges, connections, they looked good. R and R'd the gas. Boat started right up, idled fine.

    I drove it for about 30 minutes going in and out of safe mode. It idled fine.

    So I replaced the impeller which looked fine and cleaned the what appeared to be stuck thermostat which worked at temp so in leiu of a local part re-used it.

    I seen to notice the motor not smoking as it should that nice two stroke smell. So I checked the oil pump. The bleed screw allow oil to drain into the pump however at 1,500 rpm there is no oil on the down stream side of the pump.

    Is it cleanable and how much damage did I do to the motor? It starts fine, runs like poop. Won't idle. I can't get most parts locally, so I'd prefer to fix it if possible.

    Thank you in advance.


  • #2
    Re: 1988 Yamaha 2 stroke Outboard won't idle now.....

    If alarm is not going off why are you calling it a safe mode like it went into with the buzzer going off?
    Have you tested your alarm system to see if it is still working?
    Pick up a Yamaha service manual for your motor if you plan on working on it yourself, or do lots of forum searching and reading to see if you can find your problem.

    Never keep running a motor that has a problem, you may need to start testing to see if the motor is still sealing the cylinders properly


    • #3
      Re: 1988 Yamaha 2 stroke Outboard won't idle now.....

      I have a manual which led me to the oil sensor and pump via it's connected to the overheat buzzer along with the cooling system.

      And yes I am afraid that I fried the motor already. I was researching a forum after following the manual step by step instructions on checking cc's of oil put out at 1,500 rpm's with linkage to carb disconnected. I got zip. Of course in some forum ran across the person making the suggestion said to plug a separate tank with 1;50 mix onto the motor. That makes a tremendous amount of sense, the manual left that out.

      I'm able to compression test it which I did when I bought it, 105 straight across the board.

      I was reading about carbs and E10 gas. I had no idea. When I un mothballed it restart it, it ran a little ruff so I went ahead and checked the fuel system, dumped the tank etc. E10 looks like sludge?

      I put a new fuel/water separator on. But, the only filter besides the fuel water separator is the a small plastic clear filter bolted to the motor, which appears unclogged.

      When I first started the motor I noticed it burning oil as it should. But, by the time I finished test driving it which was once around the lake, I see enough or smell enough 2 stroke.

      I'm gonna test the compression, and pull the oil pump. The bleed screw bleed just fine with a slow steady yet small amount of oil when I opened it 3 to 4 turns. Yet no oil on the out side of the oil pump.

      I'm gonna pull it and check for sludge/debris.

      I really like this motor, when it ran, it ran great. So if I can't fix it, I'd like to rebuild it, if it makes financial sense.

      I can't think of a better time then the present to learn all the peripheral systems.

      Thank you so much for you suggestion, please continue.



      • #4
        Re: 1988 Yamaha 2 stroke Outboard won't idle now.....

        And of course I'll check the alarm and I have a lazer temp gun as well. So far the motor is not even hot to the touch but runs terribly rough. Right now, I'm saying the oil pumps fried and the carbs could be clogged. Is carb cleaner worth attempting?


        • #5
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          Re: 1988 Yamaha 2 stroke Outboard won't idle now.....

          oil pump is gear driven so it is hard to fry, may have plugged lines or check valves though.

          Carbs need to be pulled and cleaned if you had fuel problems along with the entire fuel delivery system and tank