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-   -   7.4L MPI Engine Warning Alarm (http://www.mariahownersclub.com/forum/mercury-mercruiser/671-7-4l-mpi-engine-warning-alarm.html)

ShabahZ280 02-01-2008 09:25 PM

7.4L MPI Engine Warning Alarm
 
One of my winter projects is to find out why my warning alarm isn't working. Supposedly the alarm sounds for 2 seconds while starting. I'd first like to confirm that Mariah put one in, and second, I'd like to find out why mine isn't functioning right!

Anyone with this engine that could help me out?

Mark 02-01-2008 10:59 PM

Mine stays on untill I start the motor. But thats on my little 182 with the 4.3 good luck.

bill.deweese 02-02-2008 02:01 AM

My alarm is located in behind the stereo/hour meter console below the throttle. I have actually disconnected it at times when I was working on the engine because it can be annoying, and then re-connected it when done. Perhaps someone just left the annunciator disconnected.

dwmax 02-03-2008 12:07 AM

My 2001 350 mag mpi has one. The question is did the previous owner disconnect it or take it out? but you should have one on there I am pretty sure that is a standard part. ;)

ShabahZ280 02-03-2008 05:49 PM

That's what I figured. Why would they put things like window defrosters, power hatches/seats, and keyless igntions on a boat and not equip it with an engine warning alarm? :shakehead:

I guess the question is now, where is it? Man, if I didn't have to host a superbowl party, I'd be working on it and making some progress!!

dwmax 02-04-2008 12:56 PM

I feel real sorry for all you New England fans. But I am real happy to see such a great upset by New York. Man that game was how a super bowl is suposed to be really close all the way down to the end. What a great upset. I am really a Indianapolis colts fan ever since I was little but I was cheering for the giants of course its Payton Mannings brother Plus I do like the under dogs :yes_grin: :wink_thumbup: :punch_out:

indykoch 02-04-2008 03:19 PM

Sweet!!! Another Colts fan!!! Yes, that game was great! I'm still in shock, but I'm convinced the entire Patriots organization is full of arrogant as_holes with no class. Go for it on 4th and 13 instead of kicking a field goal??? Walking off the field before the final snap? Didn't they make the other teams suffer through the motions while they were running up the score? It was so great to see the Giants pull it off. How proud do you think Archie Manning is?

Sorry for the unrelated rant, Chris. I believe the engine alarm is standard on ALL Mercruiser and Volvo engines. It's up to the boat manufacturers to install it, which I'm sure Mariah did. Sounds like a bad connection to the alarm or switch. Good luck, keep us informed if/when you find the problem.

dwmax 02-04-2008 08:14 PM

I was born and raised in Indianapolis and a die hard fan still. I cant explain how happy I was to see the giants win last night. I agree with you on the arrogant a**holes the patriots are and was extremely happy to see brady hit the ground so many times including that last sack before the end of the game man he was hit hard ha ha but not to rub it in on the rest of the patriots fans (sorry). Its almost like the coach was throwing a tantram thats why he walked of the field before the acual end of the game what a poor loser.:punch_out:

ShabahZ280 02-05-2008 01:22 AM

3 Attachment(s)
OK, I went up to the boat today and checked things out. Here's what I saw. (Horrible pics, from my cell phone camera, plus using only a LED headlamp and taking pics upside down!)

There's two connectors that are empty. One is a purple wire, which is connected to the ignition, the other is a black wire that connects to the blower circuit. I'm assuming black is the ground. Yet the alarm piezo is still there hooked up. I checked the Merc manuals and the alarm is connected with a tan&blue wire and a ground. Which is weird. Do I appear to be missing something?

Can anyone verify this?

WetWilly 02-05-2008 08:03 AM

Hi Shabah,

The piezo appears to be a combination alarm for the low oil pressure and water over-temp warning systems.... as you can see, the Tan/Blue wire should be the ground path and go from the piezo to the water temp heat switch then to the oil pressure switch and power is provided via a purple wire probably from the ignition switch.

This explains why the alarm comes on when you first turn on the ignition, no oil pressure, alarm on, and as soon as the motor is running and the pressure comes up, alarm off. It should also turn on if there is an over temp condition as well.

I’ll look at my wiring tomorrow to see if my wiring color codes match yours.

In the mean time, since the piezo is 12v powered, I would try disconnecting it from the boat wiring and applying 12v directly to it to see if it's still working. If it works, check the black wire for power when the ignition is turned on. If power is present then the wire being black is probably a color code mix-up. The last thing is to trace and verify the continuity of the Tan/Blue wire. Personally I think someone got the black and purple wires mixed up but you may have a bad oil or temp switch too.

Good luck,
WetWilly


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