digginfool
Well-known member
I'm starting to hate carmotor boats. My aircraft boat ran for years without any serious issues save for one starter and a prop mounting plate. My carmotor boat has nearly made me famous. :lol: So, back on February 24, I'm out riding with four other boats late at night when we decide to head to another camp. I start to take off and just as my boat is about to get up on plane, it falls back into the water. Thinking I may have run out of gas (I had been running all day), I looked down at the tach but instead of being at 0, it's bouncing off the rev limiter. I let off the gas, stop and think for a second, press the pedal again and nothing happens. Look over my shoulder and the prop is barely turning. Crap. Turn off the engine, spin the boat around in a narrow trail ( by myself nonetheless since nobody is willing to get in the water on this rather cool evening) and then get the boat towed in. Obviously, something bad has happened inside the gearbox which turns out to be the input shaft; sheared at the gear. Even though the box was out of warranty, the manufacturer paid for shipping both ways and made the repairs at no charge. Big shout out to Shane and Ballistic Geardrives! Knowing that my boat was going to be down for at least a month, I start my search for a new tuner and find someone who actually does offer software and tuning services for MEFI 6. It did require purchasing a new ECM so I got the ECM and installed it on the engine so I could download the calibration files to my laptop. Plug in new ECM, turn key, nothing. Uninstall new ECM, reinstall old ECM, turn key and everything good. Swap ECMs again and new ECM is still dead. Ok, so must be a conflict of some sort so I put old ECM back in. Now it don't work. After several conversations with the tuner company, I send both ECMs out. Tech calls me and says nothing wrong with either ECM; they test out just fine on the bench. Check your harness. I happened to have the GM MEFI 6 Service Manual (the Internet is a wonderful place) so began testing each and every wire that would have anything to do with the operational capability of the ECM. I had voltage when and where I needed it. Functionality was there when I grounded or applied voltage to various pins on the harness. Still, nothing from the ECM. Now I'm talking to the engineer from Marine Power, a retired engineer from GM Delphi. He's at a loss. Finally, I decide to get a back probe kit because the only thing that makes sense is something is happening when the harness is connected (with the GM guy's direction, I had taken apart the main harness plug and visually inspected a half dozen pin connectors). I hook up the harness to the ECM, turn on the key and start to back probe each of the critical circuits. All check out except one; the battery feed to the ECM. Checking voltage with the connector unplugged you get a full 12.6 volts. Plugged in to the ECM and voltage dropped to 2.2 volts. Now I know either I've got a dead short inside the ECM or the wire from the battery is compromised. Unless the tuner is lying to me, since the ECMs already checked out on the bench, it's the wire. Another consultation with the GM engineer and he provides me info on a wire in the harness that isn't used in my application. Since there is no way to know where the battery feed wire is compromised, I remove the pin, cut the wire from the harness, remove the unused pin and move it to the battery feed position then extend it to the battery. Voila! Turn the key on and the fuel pump pressures up. While all of this drama was playing out, the gearbox arrived from Ballistic and I reinstalled it along with the prop. Pulled the boat outside to do a test run and make sure my pitch was right. Turn the key on, wait for fuel pressure to build, hit the starter, engine starts and runs for about 3 seconds and turns off. Dammit man! Can't I get a break? Hook up Diacom and the engine is loaded with trouble codes, most of which deal with low voltage or short. Now I'm thinking I need a complete harness but I speak to the GM guy one last time. He tells me to clear the codes and try again. Doh! I know better! I'm kicking myself in the ass all the way to the boat. Hook up the laptop, clear the codes, turn the key and engine fires right up, purring like a kitten. Do some run ups, turn it off, check for codes and ECM is clear. I'm back in business! But, the more I think about it, give me two mags, 12 spark plugs and let me go to the swamp. :lol:
