At this point I'm just looking for any suggestions to try. I've been having problems with my 1999 175 EFI (serial #0G944199) for well over a year. I've had it into the local Mercury mechanic twice, spent over $2000 already, and still don't have a clue what's wrong. Every time I take the boat out, the motor will always run fine the first time I start it. It will start and run fine whether I have it going for 2 minutes or 20 minutes, whether I'm idling the whole time or running WOT. Once I shut the engine off that first time, that's when the guessing game begins. Will it start the 2nd time? What about the 3rd, 4th, or 5th? I just never know. There are times I can start the motor 4-6 times without a problem and it will run fine each time. But inevitably it has problems. I'll go to start the motor and it'll either start and run for a very short time, or it will not start at all. Then the beeping begins. That's inconsistent too. Sometimes it will beep when I turn the key to run, other times it will start beeping when I'm turning the engine over, and still other times it will start and then will beep before dying. This past weekend I even ran into another issue. The motor would start, it would run for anywhere from a few seconds to a minute, and then it would die, but it wouldn't beep each time. I'd restart it, begin to idle out, and it would die. Sometimes I'd make it 10 yards, other times I'd make it 100, but it would always die. Sometimes it would beep, other times it wouldn't. And my tach wasn't acting right. When I would try to turn the motor over, my tach would start rising without the engine even running. One time I had the engine running at idle speed but the tach was at 3200 rpm, obviously not correct. The mechanic has had a fairly hard time getting it to replicate in the shop, but did get it to happen once or twice out on the water. For me, it happens every time I'm out and it ruins my fishing day more often than not since I then can only use my trolling motor to move around. So far the mechanic has:
changed spark plugs
replaced the low oil alarm module
checked compression
checked fuel pressure and made sure it stayed the same overnight
replaced a temp sensor
After it was in the shop the last time, the mechanic said I should take the ECU off and send it in to be checked. I did that and was told that it checked out good when cold, but there were some errors when it would get warmed up. They rebuilt it ($1150) and I reinstalled it this spring, feeling like the issue would finally be taken care of. First time out, just to do a little fishing and test the motor, it started and ran fine. I started it 3-4 times that day. Again, it made me think that the problem was resolved. The next time out, this past Thursday and Friday on a trip with a friend, it only took a few hours on the first day before it started having problems again.
I have a feeling it is something electrical. Why does it always work when I first take the boat out? Is it because my starting battery is fully charged at that point?? I had the battery tested last year and was told it was fine, but I just had a trolling motor battery fail and I think they were bought at the same time (before I owned the boat), so I'm thinking about replacing the starting battery no matter what. I have tried not even turning my main depth finder on (Helix 9 Mega SI) to see if that makes a difference...it does not. From what I understand, the beeping should either be caused by overheating or low oil. I can guarantee it's not overheating because I've got good water pressure and there are times it will act up and I haven't had the motor running for over an hour and even when I did it was only for a few minutes at idling speed. I'm grasping at straws trying to figure this out and get it fixed with as little additional cost as necessary. Is it oil related (air in the oil tank, float stuck...just a couple ideas that I have yet to test)...could it be something in my ignition wiring harness? Any advice or suggestions would be greatly appreciated. I do have a few videos I took with my cell phone the last time I was out that shows the problem. I can text or email them if anyone thinks they would help. Thanks!