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115 Merc alarm and enging bucking-gctid810564

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    115 Merc alarm and enging bucking-gctid810564

    Had my new F18 out last nite, and out of the blue I got an alarm (3-4 beeps) and the engine cut right down and started bucking. My first inclination was that I sucked in something that was blocking the water intake, but it was pumping fine. I raised the engine to be sure something wasn't on the prop, and that was good. After that I just pulled it into neutral and back into forward, and everything was fine. I was trimmed up kind of high, as I'm still getting used to the boat, etc., so maybe it got aspirated? Just looking to satisfy my curiosity here, before I trailer it out and take it to the dealer... Any ideas on this?
    '17 F18 - 115 Merc

    #2
    Don't touch it.....DEALER time, let them figure it out.
    Vic Stewart SN
    Past Commander
    Cape Fear Power Squadron
    Ft Myers Power Squadron
    1998 2859 7.4 L/B2
    Raw water cooled

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      #3
      Oh definitely. Just was wondering though. There can't be 3 hours on that engine.
      '17 F18 - 115 Merc

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        #4
        Update: Dropped boat off at dealer last Wednesday, and they put it in the water to try and duplicate the engine bucking and alarm. Got the call, my transducer was supposedly mounted too close to the engine, causing aspiration at higher speeds. It's a Garmin Chirp transducer - one of those long ones. I've used them many times, on many different boats, but was advised that due to the hull configuration of the Elements, that mounting it where I had it would cause issues. So after getting the entire history of the engine for it's 4.8 hour life, I take the boat home, pull the transducer, throw her in, and go for a ride. All is well, until > 5200 rpm, then the engine alarm goes off, etc. I noticed that at higher speeds, the water is not shooting out the pee hole as fast as it should. In fact, it sometimes went down to a trickle. No alarm though. So, back to the dealer for an impeller. Hopefully this will do it, and I'll definitely have to remount the transducer farther from the engine.
        '17 F18 - 115 Merc

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          #5
          No bucking, just an overheat alarm? Something is funky; these sound like different problems that should not be occurring on a new motor. Also, bucking and an alarm is a strange reaction to cavitation. Cavitation, which I assume what you mean when you say "aspiration," is when air bubbles interrupt the smooth flow of water over the propeller, thus reducing the resistance of the water that the propeller is "cutting" through, causing the engine to suddenly rev higher. I wouldn't call it "bucking," and it should not cause an engine alarm and should not, unless it occurs for a seriously long time, do any damage to your impeller.

          Not trying to cause alarm (excuse pun) regarding your new boat, but the symptoms (based on my understanding of your description) and explanation don't add up, IMO.

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            #6
            Aspiration... Meant cavitation; my bad. The "bucking" is the engine going into "guardian mode". I spoke with the service manager last nite. They water-tested the boat and did note that at higher rpm's (4800+), the water wasn't flowing as good as it should from the pee hole. At 5600, the engine alarm sounded and went into guardian mode, then back out once the revs came down. They pulled the boat, and the impeller was worn due to getting too warm, so they replaced it, threw her back in and ran the living daylights out of her. No issues at all. I can somewhat agree that maybe a large transducer like that MIGHT cause some issues as I did have it mounted very close to the engine. In fact, the manual for the transducer does advise that mounting too close can cause issues. But, I'm having a hard time wrapping my head around the fact that it caused cavitation to the point where it would damage the impeller. But, for all anybody knows, the engine could've been run and the impeller screwed during the dealer prep process, a test drive by another potential customer, or it could've been defective from the get-go. As we all know, it only takes a few seconds of running an impeller dry to damage it. I suppose it's one of those situations where we'll never know. Picking up after work today, just in time for 3 days of rain!
            '17 F18 - 115 Merc

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