warning buzzer install struggles

GTRiem

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Jul 1, 2009
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8
Hello,

Hope everyone is having a great Christmas and New Years.

My Dad just had a marina repower his Pursuit from the old 1986 350 mercruiser/alpha1 to a supposed 2001 350 mag mpi & new bravo3.

The swap seems ok, it runs and all- but the boat came home before the low oil pressure/over heat/ low outdrive lube alarm was in hand to be installed.

Was supposed to be an easy job according to the mechanic from the marina, so I volunteered to giving the install a go without much success.

After peeling back wire loom and crawling all over that engine I guess I am at the point where it appears that the wire harness on the new engine and the original harness from the boat do not have the needed wire to be just plug and play.

The elusive tan/blu I can't find.

The alarm is wired to key on 12v and a new wire run back to engine. Can not seem to find the wire to attach to from the engine harness.

I see on the gear reservoir a Blk wire & a tan/wht.
On the t-stat housing there are 2 sensors, 1 - has Tan wire only, 2nd has a plug with Blk wire & Ylw wire.

The oil switch I'm not sure which one it is, there is a sensor by the distributor with Blu wire, there is a sensor on left side of block also with Blu wire.

There are 2 unused wires I found on the harness, 1 is a single gray (is this a tach lead?)
The other is a Blu/tan some diagrams say its a oil pressure others trans temp...?

So are there any options to making this alarm function as intended? Can I splice into each wire at the sensor and attach to the alarm lead? Or am I looking for another wire to join to?

Is the ECM part of this ? I don't want to mis-wire something and cause damage

What is the sequence of events for the alarm?
Key on - alarm sounds due to low oil pressure, engine on/oil pressure comes up- alarm silent?
Alarm comes On if any of the 3 sensors trigger resulting in grounding to sound alarm?

Hoping to figure this out soon, this boat is supposed to leave Jan 20 from cool Michigan for Florida

Thanks for any direction and advise.

GTRiem
 
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achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
First thing we need to know is what ECU the engine has... MEFI1/2 or MEFI3... Each run the alarm differently.

MEFI.JPG
The drive oil bottle should have 2 wires, both black. Next to them should be a black wire (for the ground) and a tan/Blu wire (for MEFI1/2) or tan/wht (MEFI3), for the alarm.

Oil pressure alarm switch for both systems is a separate switch, with a tan/blu wire. Some engines have a tee at the oil pressure sender (for the gauge) on the port side of the engine, below the manifold, some have a switch behind the distributor.

Water temp is done by the ECU, and it's taken from the digital sender at the thermostat housing. A 2-wire sender with a yellow and a black wire.

But the important thing, you need the wire running in the instrument harness. The 'alarm' is on pin 4. And looking at the diagram for a 1986 engine, no wire on pin 4... THIS is why the mechanic said to you 'it's an easy job'. Yeah, right!... So, you need to run a wire from the minus side of the alarm buzzer to the engine (plus side, as you correct proposed, goes to the 'IGN' side of the key. I use the + terminal on the tacho as my feed point for switched 12v for the other instruments, and the alarm). I would have a water-proof bullet connector (to make it easy the next time the engine needs to come out) at the same site as the main harness plug, and run the wire, in the engine, to the oil pressure switch, and splice into that wire (tan/blu).

Chris.........
 

GTRiem

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Jul 1, 2009
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8
Thanks Chris,

I will attempt to post some pics of what I am seeing In the hopes that there is a solution I can wrap my mind around.

I really thought it wasn't going to be a big deal either as it seems like a dumb circuit like an idiot light only noisy. The more I got into it and the more I tried to research it, just led to more questions I do have a new wire from the dash run back to the engine area.

I am not seeing a tan/bl wire anywhere in these harnesses.

I was able to connect the new alarm wire to the gear lube lead and push the float down on the sender and activate the alarm, as the sender float returned the alarm shut off. So that part of the install was "easy" lol

Also while were at it , there is a water sensor with a broken clip for the plug, part # for that?

George
 

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achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Righty oh... That's MEFI-3....

First up, the part number for the broken temp sensor (port side of the base of the thermostat housing?) appears to be -805218T

Photo 1. Bottom right, right next to the oil filter. Is that a tan/wht wire? Should be connected to the oil bottle switch.
Photo 2. (Lt Blue wire on an oil pressure sender) is for the analog gauge.
Photo 3. Appears to be an oil pressure switch, which on MEFI-3 runs directly to the ECU.

To hook the buzzer up the right place....
There should be a tan/blue wire running in the harness from the 10 pin plug (that connects to the instrument harness). That wire runs to a 6 pin plug that is the connector between the 'Starting/charging harness' and the 'EFI system' harness. Here's the diagram of it... You want to splice into the tan/blu...

MEFI-3.JPG

Chris............
 

GTRiem

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Joined
Jul 1, 2009
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Chris...whooo hooo maybe we getting somewhere here!

I have a pic of a wire plug that I wondered about but never got any confirmation about what those wires were for.

(to be fair it is holidays and the marina layed off the mechanics for the season right after our repower job as it was the last job in the shop, so quick responses haven't been happening)

I do not have a service manual yet and was working from some not so good internet wire schematics so I discounted these as they did not seem to jive with what the mechanic was saying.

Anyway, here is the pic of the plug I believe we're looking for. If this is in fact the tan/bl I needed all along I am truly embarrassed. I just didn't have enough info to make the call.

Now, where in that harness can I attach the new lead? That tan/bl is supposed to go to that big plug? There should be around 8-10" of wire I suppose inside the loom but I couldn't see it... I can splice in to it somewhere in-between?

* the serial # to engine is omo66334 if it makes any difference.
 

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achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
That certainly looks like the right wire... It's the right colour and on a 6 pin connector with all the right colours on the right pins. So I'd say yes... And you can slice in anywhere along its length...

Chris...
 

GTRiem

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Jul 1, 2009
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THANK YOU!!!

I will post back later after I run up to the shop and see how it goes.

Thanks again.

George
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
I'll be sleeping... It's 2300hrs here now...
 

GTRiem

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Joined
Jul 1, 2009
Messages
8
Chris,
Thank you so much for your help!
Was able to surgically cut my way into that rear hard to reach harness and expose just enough wire to hook it up.
Seems to work as it should.

Happy New Year

George
 
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