mulligan Posted August 10, 2020 Report Share Posted August 10, 2020 So we were out this weekend and while running from spot to spot I heard a noise coming from the motor. It sounded like a knock from under the cowling. I got of plane and idled for a bit and all seemed fine. When I went to jump back up it dogged some out of the hole and the sound came back. I shut it back down and was close to the ramp so a little fishing with the trolling motor as we headed to the ramp. When I got home I did a compression test and had 125-130 on all cylinders but found #2 plug had a bunch of carbon on it and not as wet as the others. I also ohm out the coils and they ohmed ok. Any ideas what could be causing the problem? Resent maintenance history is: Big Blue 5 hrs/ VST, mid pressure, paper filter 50hrs/ injectors serviced and high pressure fuel pump filters 130hrs. Quote Link to comment Share on other sites More sharing options...
Lap it Up Posted August 10, 2020 Report Share Posted August 10, 2020 Did you run it on the hose? Any weird noise with the cowling off? When was the last time it had NEW plugs? HPDI's and Opti's should really get new plugs every season. I also do the K.I.S.S. approach. Fuel, Air, Spark. Start with fuel and work your way down. Hopefully its something simple and not an issue with the rotating assembly. Quote Link to comment Share on other sites More sharing options...
mulligan Posted October 9, 2020 Author Report Share Posted October 9, 2020 Update. Good news, bad news. The bad news is that it was not anything simple. I checked all I could on the outside of the motor and all checked out good so it was off to the shop. The mechanic had a hard time hearing the noise until he muffled the motor. As it turns out it was the wrist pins on #3 and #5. So a new set of pistons were needed and while he was in there he put in new bearings. The good news. I was lucky to catch it before anything major happened. He said the motor was spotless on the inside which he was a little surprised by. Everything besides the pistons was perfect and not even a scratch in the cylinder walls, still had all the cross hatching. Thanks again Dale for pointing me to Pete at Cracker Boy Marine. Quote Link to comment Share on other sites More sharing options...
Lap it Up Posted October 9, 2020 Report Share Posted October 9, 2020 I was afraid it was in the rotating assy. Glad you caught it early! Is he going thru the front half or did he split the case halves? Quote Link to comment Share on other sites More sharing options...
mulligan Posted October 9, 2020 Author Report Share Posted October 9, 2020 I'm not sure but guessing he split it as it needed a whole gasket kit and crank and all were miced out. Quote Link to comment Share on other sites More sharing options...
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