I got myself involved helping someone that bought a boat with a merc 5.0 MPI. A week after he bought the boat the engine was full of water. The owner removed the exhaust, intake, heads etc but wasn’t sure how to put it all back together. So I got it all back together, it idles smooth but on start up, the alarm beeps 10 times. The owner took the boat for a sea trial against my better judgement because he said the alarm was doing that when he bought it. Anyway when he attempted getting on plane, the engine would buck, backfire etc. When he came back from the water he attempted to flush the motor but it wouldn’t start up and he called me. I could hear the fuel pump but it didn’t sound like it was picking up fuel, I checked at the shrader valve and just fuel and air. The next day I tried again and this time it started right up and idled but would idle smooth for 10 seconds and hunt. I hooked up a diacom to it and no faults. The thing I found odd was the iac was constantly at 100%. I think today I may have figured something out. The fuel lines to the separator were tight but i gave them an extra crank. Now it idles smooth without hunting or surging and the iac has started coming down to 60% duty cycle so I feel like I’m in the right direction. I had to stop testing suddenly because it started storming out. I’m still at a loss of the 10 beep alarm. I’ve never seen or heard of that before. Btw I have built like a few thousand big blocks and my share of small blocks over the past 30 years. Anyone know what would cause 10 beeps right after start up. The engine has the ECM555 if that helps.
