Help 1999 Tige 350 Mercruiser MPI Mag intermittent audible alarm questions

[Yankees39]

Hi, got my 1999 Tige 21v about two months ago and love it. Two Saturdays ago we were out on the river andthe serpentine belt started splitting so limped back to the dock and that was it for the day. As we slowly made our way to the dock the belt continued to fray and belt particles got all over the hoses and my engine. Last week I replaced the belt and while I was at it I replaced the impeller, oil and spark plugs. I also installed a 10" sub and 600watt amp that runs the sub. The power is being pulled from the single boat battery at the back of the boat.

Once I got the boat put back together from the sub install, impeller, plugs, oil and belt repairs we went out last Friday to test it out. I started getting a softer audible beeping warning sound. All gauges were at normal working conditions temp, oil , voltage all normal. It beeps at RPMS 2500 -3000 and beeps every 3-4 secs. Sometimes it will beep 4 or 5 times sometimes only once. I can run it WOT at 4000 - 5000 RPMS and it won't beep but when I pull it back to 2500RPMS it starts beeping once every 3 seconds for a few times then will stop. We pulled the air filter cover and the round silver air filter had that black serpentine particles all over it. I cleaned it off with a rag and the beeping went away for the rest of the day. Went home later and sprayed brake cleaner in the silver air filter and blew it with the air compressor to clean it real well.

Put the boat in the water tonight to do a final test run before our big trip to Lake Ouchita for Labor Day weekend and the boat is back to beeping at me again at the same RPMS 2500-3000. Once again the engine seems to be running crisp and will run great no audible beeps or sluggish running at idle or WOT. and even at 2500-3000 RPMS it runs fine just beeps every 3-4 seconds for different durations then sometimes stops beeping at those RPMS.

Any ideas what could be causing these beeps? We have a 4 night camp out and 3 full days on the lake and counting on the boat for 3 families and I am hoping it runs good the whole time. Any suggestions would be great. I'm going to try to get it into a mechanic to scan the engine but not sure if I will be able to find one to scan it in the next three days. I'm fairly new to boating and just got the Tige and am getting hooked fairly quickly!!!! They are way to much fun for me and my 5 yr old and 3 yr old!

Engine serial # is 0L390830

Thanks in advance for the help.

[Bakes5]

Hmmm...kinda sounds like an intermittent low voltage situation. Have you checked all the wire connections on the alternator? You might have a loose wire or else a wire that has broken but is held in place by the heat shrink tubing. I have a pesky wire on the alternator that has broken no less than 3 times. I think the wire is a little short so it puts stress on the terminal and it fatigues. Yours might be holding on by a thread. Is your battery still good? Try disconnecting the amp as well.

[Yankees39]

When I went out today it was for a quick spin and should have disconnected the amp from the battery to see if that fixes the problem. But I was so frustrated and worries about the upcoming trip that I didn't think of it till I had gotten home. I'll try that in the next day or so when I get time to put it back in the water. What's funny is it only goes off at those certain RPMS 2500-3000 roughly. I'm no serious mechanic far from it but that seems a little strange to me. I had the battery tested a month ago and was told the battery was good. I definitely need to unhook the amp wires from the battery since that's one of the things that has changed since this beeping just started occurring.

Thanks

[Yankees39]

Well I put the boat in real early this morning and disconnected the power supply for the amp at the battery and the beeping was still there.

I am going to try to see if I can get it scanned before our big trip this weekend.

All gauges read normal at the RPMS that it beeps at. I wonder if this could be a big problem that could ruin the engine if I run it on our trip this weekend without knowing why it's beeping. Engine seems to be ruining really good. Had a friend that knows a good amount about car engines out with me last Friday and he said it sounded like the engine was running real strong and smooth. This is very interesting.

Thanks for all the help

[Bakes5]

Check your alternator wires. There are a few smaller that could be the issue as well. Try to move the taps when it is beeping. When my alternator wire is broken the taps won't work.

[Yankees39]

Taps will move while it beeps. I have it at the mechanic he scammed it and it didn't read any errors while it ran. All the major vital readings were normal. He was using a newer software scanner and it wasn't letting him look at previous error codes. He wasn't sure if this motor stores the previous codes or if his software was to new. He has another mechanic that will be in tomorrow that has software that is a little older that might be able to read past error codes and will run it tomorrow. Thiat is at least what i understood from the conversation and can remember. I could be interpreting it slightly wrong. He had the thousands guy that if he can't get it to flash a error code or see previous errors then one problem it could be is possible a faulty depth finder and I'm getting warnings from that. ??? Who knows, it does make me feel better that the oil pressure engine temp etc all major vitals was reading normal.

Thanks for the help

[SATige]

Could it be the "air idle sensor"? I have the same motor in my 2002; a couple of years back I had an alarm go off but all was normal otherwise, turned out it was a bad sensor. Maybe someone here has more knowledge about the sensor that could determine if it could be the culprit. I hope you fix it in time for the weekend, I'm familiar with your pain, it seems my boat only gives me trouble when there's a party relying on it.

[Yankees39]

Well got the boat back from the mechanic. It scanned a error 45 which I guess is a coil driver fault. The engine read good all vitals look, good temp, oil pressure, voltage all checked good. He said he checked some of the wiring and all checked out. He wasn't sure what the problem is. He couldn't get the code to trip in his water pit. The error code displayed in a previous code or code history.

With saying that the engine runs good but we are out on Lake Ouchita today and it started right up all morning but the last two times I have turned it off I have to put it in neutral and give it gas to get it to start up. It fires immediately but dies like it isn't getting fuel. Then I put it in neutral give it has turn the key it revs strong fires up I give it has for like 3 secs then it will idle and run as normal. Only have this problem starting it. Everything else seems good.

Oh when we first ran it it beeped again in the beginning when RPMS are below 3000psi then it goes away after beeping 3-6 times. Then turned the boat off after like ten minutes to let the little ones swim. Then it hasn't beeped since but now we have this starting issue!!

Welcome to boating eh! Boat ran good for the first two months now for our big trip issues. Murpheys Law ��������. My solution is to not turn it off. ✋����

[boatwakes]

Idle air control valve mercruiser part number 803149 (starting issue)
Code 45 is gonna be a bitch to find. See attached:
No clue why they're sideways, good thing I can turn a wrench.

[huntingwiley]

I just had this same issue. Changed the IAC and still had problem. Took the Fuel injectors off and has them clean\rebuilt and it starts right up now. Like new. Mine is a 2003 Merc 350 MAG MPI. It cost 20$ an injector at my local shop.