Continuing issues with '99 175 EFI

[coreynov902]

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!

[TAGG]

I think youre going to need a mercury service manual & a dva meter to figure this out. Intermittent problems like this usually arent going to get figured out in the shop unless it's a coomon pattern failure that most experienced techs would recognise. I would bet money the warning horn & tach are going to ultimately be symptoms of the real problem. If the warning horn is a constant beep, it indicates overheating. If it's intermittent beeping, it indicates an oil injection problem. The oil injection pump motion sensor sends a signal to the oil injection warning module if the pump shaft is turning. The module matches this signal up with the ignition signal to the #2 cylinder coil. It sounds like the stator, trigger, switch boxes or voltage regulators are going to be involved. The easiest starting point is to look at the voltage regulators on the back of the powerhead. If they look like they"ve been hot or the wiring connectors are burnt, thats a good starting point. If that all is working properly, you will need the manual & a dva tester to go much further.

[JOE54]

the first thing you need to do I find someone who will test and not guess shame you spent that kind of money and still have same damn problem, check see if charging system if working, most like ly gonna be bad switchbox or both , but voltage test would need to be done when problem occurs , TEST AND VERIFY, NOT GUESS AND HOPE

[coreynov902]

I appreciate the feedback guys. Sounds like I'll need to take it back into the shop since I am definitely not a mechanic. The guy who has worked on it said he runs into 2-3 cases like this a year, where the problem is very hard to isolate and fix. I may just have to get him to take the boat to the lake instead of having him test in the shop since he's had a hard time getting it to replicate in the shop. Thanks again.

[JOE54]

lake

[nitromorris]

What cranking battery are you using ?

[coreynov902]

I don't know the exact model since I'm not at home. It's an Interstate Marine cranking battery. It was in the boat when I bought it almost 3 years ago. The boat also had 2 Interstate Deep Cycle batteries in it when I bought it and I just had one of those batteries go bad on me a couple weeks ago, so I replaced both of them. I'm contemplating getting a new starting battery as well, but it tested fine last fall when I had it checked, and if the battery is still good I don't see why I should replace it.

[Tx 201]

Pretty convinced that the older EFIs are really just crap between the carbs days and full on fuel injection and computer run like the Optis. I have been fighting mine for years, almost get it fixed and then it is something else. My son graduates college in two weeks which will put an end to 12 consectuive years of paying for colleges and weddings for the kids. Might be time to put that money toward a new or newer motor and let someone that likes the 2.5s for racing application have this one.