Mercruiser 7.4 MPI Engine alarm

Kreole that makes sense. Did you need to put a wrench to it or just get a good grip and twist? :)

Mine has a gray "pig tail" that's about 4-6" long with a connector on the end of that based on what I can tell from the mercruiser schematics. It's connected to the port side of the block.
 
DaleM said:
Kreole that makes sense. Did you need to put a wrench to it or just get a good grip and twist? :)

Mine has a gray "pig tail" that's about 4-6" long with a connector on the end of that based on what I can tell from the mercruiser schematics. It's connected to the port side of the block.
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Wrench it.

The 380 I worked on had V-drives so it is located on the port side, but our motors are reversed.

Our problem was on the port motor and man it was very trying to squirmy down next to that damn holding tank:smt089
 
Our problem was on the port motor and man it was very trying to squirmy down next to that damn holding tank
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Right - and mine is going to be between the port/sb engine in about 6" of space. I got intimate with my generator last weekend before giving up because I didn't have a good visual on how it connected. I'll be taking down a mirror and a light so I can figure out what tools I need.
 
I'll be taking down a mirror and a light so I can figure out what tools I need.
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Good Idea:thumbsup:

Well I'm still on the hard waiting on struts to be shipped later this week. The repair facility is going to start on my bottom job this week. I'm going to put a few more coats of cleaner/wax on her towards the end of the week. Hopefully I'll be able to splash sometime next week.

The oil spill hasn't really affected my boating area so, I can't wait to get back out there. I haven't ridden on a boat in almost a month:smt013.
Actually, I'm on the board at my marina and we did a cleanup this weekend of our marina, but it was JUST in the marina so I don't count a ride in a little 16' flat boat as a "ride":smt009.
 
I was actually going to ask you how you guys were doing with the oil offshore. That's such a disappointment - I love the seafood down there and I'm sure it's going to put a real hamper on things. I couldn't get out this weekend due to 30+knot winds and a tide that had some boats sitting on the bottom. Nothing compared to an oil spill.
 
Follow us on "NOLA.com". That's the Times Picayune's website (Newspaper). That's the best website to keep up with what's going on down here.

I told my wife today, you would think that there would have been some preparation for something of this magnitude because it was bound to happen, ONE DAY:smt013.
 
Very interesting write up. We have been having a problem with an alarm on the port engine. After running a 20 mile lake all of a sudden an alarm goes off. If we shout down the port engine for about 1 - 2 min. and start it up again the alarm goes away. Any thoughs on this. Please help.:huh:
 
Connie G, that's the mystery and I'm trying to narrow down the sources. I promise if/when I find the source I'm posting my specific fix. I have another thread that I started in CSR with a topic of about whether the powersteering fluid can cause an alarm because I was getting so frustrated. Here is that thread. some of it is a little long but I was trying to keep an accurate account of what I was doing. http://clubsearay.com/forum/showthread.php?p=341310#post341310
 
Thanks Dale, please keep me posted. As soon as the boat hits the water we are taking it in to have it looked at.

Connie
 
Connie, you bet. Please let me know what they tell you. I've found a lot of "symptoms" posts with no resolution! :)
 
I´m having the same problem with my 5,7efi -97
alarm goes at 2500rpm and the engine reduces power.

was it the knock sensor wire that were your problem?

I didnt tought the alarm can sound because of the knock sensor.
 
I don't have a reduction in power. Based on this information that I found at another site I think it can alarm. I'm not positive though. I have yet to isolate it down to which sensor. I do know it's on my starboard engine.

I can't take credit for this information - I'm only passig it along.

======================

Here it some general information I put together about the warning horn systems on Mercruisers for someone else.

PS, Your particular engine does not have everyone of these Warning system Faults, But it has a lot of them, The best thing to do is to have a service manual from mercruiser for your engine to help you know what your engine really has as far as sensors go.


The 2 beeps per minute can be generated by quite a few things. Some of the error conditions will limit the available power the engine produces. The 2 beeps/minute can be generated by: cam sensor open or shorted, engine cooling temperature circuit open or shorted, coil harness wire (EST) open or shorted, fuel injector open or shorted, IAC output, knock sensor, MAP sensor, MAT sensor, oil pressure circuit open or shorted, port/starboard exhaust manifold cooling temperature circuit open or shorted, sea pump circuit open or shorted, fuel pump relay, throttle position sensor circuit open or shorted, low 5 volt power supply as well as other errors.
Best suggestion for the 2 beeps per minute is to have the dealer/shop read out the error log to see what is generating the error condition.

This table is a guick guide, showing what warning output will accompany a fault for the Mercruiser Sterndrive engines. (MCM)

Warning system Faults, SC1000 Yes/No, Audio Alarm, Available Power %, Description.

(1) Cam Sensor Yes 2 Bp/min 90% Open or short, engine must be cranking to set this fault code.
(2) ECT CKT HI Yes 2 Bp/min 90% Open
(3) ECT CKT LO Yes 2 Bp/min 90% Short
(4) ECT Coolant Overheat Yes Constant 6-100 % Engine guardian overheat condition
(5) EST 1-8 Open Yes 2 Bp/min NA Coil harness wire open
(6) EST 1-8 Short Yes 2 Bp/min NA Coil harness wire short
(7) Fuel Injector 1-8 Open Yes 2 Bp/min NA Fuel injector wire open.
(8) Fuel Injector 1-8 Short Yes 2 Bp/min NA Fuel injector wire short
(9) IAC Output Yes 2 Bp/min 90% Only with rpm
(10) Knock Sensor 1 Yes 2 Bp/min 90% Alarm sounds for 20 seconds in NEUTRAL and indefinitely in gear.
(11) Knock Sensor 2 Yes 2 Bp/min 90% Alarm sounds for 20 seconds in NEUTRAL and indefinitely in gear.
(12) Low Drive Lube Strategy Yes Steady Bp 0-100% Low oil in sterndrive.
(13) Low Oil Pressure Strategy Yes Constant 0-100% Low oil pressure strategy.
(14) MAP Sensor 1 Input High No 2 Bp/min 90% Short, no visual on SC1000.
(15) MAP Sensor 1 Input Low No 2 Bp/min 90% Open, no visual on SC1000.
(16) MAT Sensor Yes 2 Bp/min 90% Open or short in MAT circuit.
(17) Oil PSI CKT Hi Yes 2 Bp/min 90% Short, defaults to 51.7 psi.
(18) Oil PSI CKT Lo Yes 2 Bp/min 90% Open, zero oil pressure.
(19) Overspeed Yes Constant RPM Limit Engine over rpm limit
(20) Port EMCT CKT Hi Yes 2 Bp/min 90% Open, defaults to 32 degrees F.
(21) Port EMCT CKT Lo Yes 2 Bp/min 90% Short, defaults to 32 degrees F.
(22) Port EMCT CKT Overheat Yes Constant 6-100% Overheat condition, 212
degreesF(100 degrees C) limit.
(23) Sea Pump PSI Lo Yes Constant 6-100% Low water pressure strategy, defaults to 43.4 psi.
(24) Sea Pump CKT Hi Yes 2 Bp/min 90% Open.
(25)Sea Pump CKT Lo Yes 2 Bp/min 90% Short.
(26) STB EMCT CKT Hi Yes 2 Bp/min 90% Open, defaults to 32 degrees F.
(27) STB EMCT CKT Lo Yes 2 Bp/min 90% Short, defaults to 32 degrees F.
(28) STB EMCT CKT Overheat Yes Constant 6-100% Overheat condition, 212 degrees (100 degrees C) limit.
(29) Steer CKT Hi Yes No No Open and short.
(30) TPS1 CKT Hi Yes 2 Bp/min 90% Short, signal to 5v+, engine will not start. Refer to data monitor screen.
(31) TPS1 CKT Lo Yes 2 Bp/min 90% Open.
(32) TPS 1 Range Hi Yes 2 Bp/min 90% Above 4.8v, 994 counts.
(33) TPS 1 Range Lo Yes 2 Bp/min 90% Below 0.5v, 35 counts.
(34) Trim CKT Hi Yes No No Short, high range, visual warning on SC1000 only.
(35) Trim CKT Lo Yes No No Open, low range, visual warning on SC1000 only.
(36) 5 VDC PWR Low Yes 2 Bp/min varies Short any 5v+ to ground.


Here's some other information that what will sound the alarm on a mercruiser Engine.
Constant tone alarms are for:
1.) engine coolant temp overheat,
2.) low engine oil pressure,
3.) engine overspeed,
4.) exhaust manifold cooling temp overheat
5.) sea pump PSI low.
Note #5 is known to be a common problem, It's been said that this fault might not show up in the fault history section of the scan tool.
If that is the case then the only other way to know if this is your problem, is to watch this sensor live as it happens out on the water with the scan tool hooked up to the engine.
Also make sure all the Battery cables are clean & tight plus a fully charged Battery is very important.
Check the water pressure sensor threads for any paint, Also check the sensor to see if it has come loose or Has a blockage of some kind.
If any sensor loses it's ground it could sound the alarm. As an additional test, try adding a ground wire to the sensor threads to stop the horn.
Or there is a chance you could have picked up or created some air bubble for a short time, until the boat slowed down, possibly due to the brass water pump impeller Housing could be failing do to deep grooves inside housing creating a disturbance with the water flow.

Constant beep alarms are for:
1.) low outdrive lube level.

Two Alarm beeps every 60 seconds are for:
1.) Faulty cam,
2.) IAC,
3.) MAP,
4.) MAT,
5.) knock sensors.
6.) open/short in the engine cooling temp circuit
7.) open/short in fuel injector wiring circuit,
8.) open/short in oil PSI circuit,
9.) open/short in exhaust manifold cooling temp circuit,
10.) open/short in sea pump circuit,
11.) open/short in throttle position circuit
 
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Yes it definitely was the wire/ connector to the knock sensor; cutting the wire back, eliminating some frayed strand and reconnecting the connector has done the trick. This would have saved me a couple of thousand $ if detected early/ or some of these responses would have come a year ago.

Hope that my nightmare has helped others.

Henning
 
hnorup said:
Yes it definitely was the wire/ connector to the knock sensor; cutting the wire back, eliminating some frayed strand and reconnecting the connector has done the trick. This would have saved me a couple of thousand $ if detected early/ or some of these responses would have come a year ago.

Hope that my nightmare has helped others.

Henning
Click to expand...

Dale, it screws in like a spark plug, then you connect the little clip to it.

Make sure you have actual "Wire" under that insulation, cause like I said in the earlier post, the insulation pulled back a bit, and there was no wire connected to the clip. Good Luck
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Ah Haaa!!! The Kid remembers some things:thumbsup: I'm a wheelchair selling, Strut and Shaft trashin, wanna be boater, but I'm learning.

Henning, now pay attention when you go slightly above 3000-3200 rpm and see if you still alarm, if not, you have solved your problem my friend.
 
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On mine, it's on the port side of the engine not far below the exhaust manifold. You'll know it because the sensor is attached to the side of the block and there is about a 4" long cable extension that comes off of it. At the end of that extension is the connector that everyone talks about.

In this diagram it's #37.
http://www.mercruiserparts.com/Show...inbr=8093&bnbr=40&bdesc=Electrical+Components

Scroll down to the part number and click on it - you'll get a picture of what I'm describing.
 
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Just thought of one thing - based on your signature your engines will be in your boat in reverse of mine so keep that in mind.
 
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