1995 90hp ELPTO Overheat alarm weird sound

[Trampstamp]

Greetings once again to you fine folks who know more than me.

Had an overheat alarm go off on the first shakedown run, have since replaced what appeared to be a non-functioning thermostat. Put her back in the water for a second shakedown, still need to fiddle with the idle to get it dialed in, but after running the boat for about 20 minutes, everything from idle+ to WOT, the overheat alarm sounded again, but this time it was kind of buzzy and scratchy sounding, not the clear and annoying "BEEEEEEEP" like I got the first time. So I was close to the dock, so I turned off the motor and went in on the TM. I started the boat again to briefly power load onto the trailer, the buzzy alarm came on again. I pulled the boat out of the water to a washdown station at the immediate top of the ramp, hosed boat and trailer down for a minute or two and then started it again to flush the motor (was running in saltwater), and the alarm did not make a peep for the ~2-3 minutes I was running the motor in the parking lot.

This motor runs a 120 thermostat; the block did not feel anywhere near hot, maybe 90 degrees to the touch, constantly strong telltale...at this point I'm suspecting it is the sensor itself is faulty.

All that said, where the hell is the temp sensor?! I've looked a diagrams and as near as I could tell, it is located right and above of cylinder #1 (the brass bolt in the first photo), but that wasn't correct, the only other thing that looked "sensory" was below the thermostat housing (the grey wire in the second photo)...any insight is much appreciated!

Dan

P.S. I will additionally mention that in my initial workings on the boat (in my driveway, before I ever started it), I did at one point get the same buzzy continuous alarm after just turning the key into the on position, thus further driving my suspicion to faulty sensor.

Thanks!

 

[racerone]

That brass pipe plug is where you would get a signal for a water pressure gauge.----The grey wire is for temperature alarm.-----The first step on a ---" new to you boat / motor " is a new water pump kit.-------Just a golden rule !----Will save you a lot of gold.

 

[wn6ngp]

Since this motor has been used in salt water make sure that the lower unit will drop when you loosen those bolts holding it on. On my 2000 model the steel locator pins had corroded to the lower unit and it was almost impossible to drop the lower unit. I had about 20% salt time. Your motor may well not have this problem but it is easy to check and you don't want to discover this problem when you need/want to replace the water pump.

 

[Trampstamp]

Thanks racerone, that was my best guess!

Sorry, didn't clarify.

Have already replaced impeller and it was never ran in saltwater prior to me owning it (shakedown runs in my local bay, since my nearest lake is 2.5 hours away.)

 

[Trampstamp]

UPDATE - BREAKING NEWS!

With boat sitting in driveway, I jiggled the Temp sensor wire where it goes into the cooling system and it caused a continuous buzzy alarm sound.

After disconnecting the temp sensor wire (Tan/Blue stripe) from the connection point at the bottom of the electrical panel, the noise kept happening.

The remaining two wires are another Tan/Blue stripe, and one is just Tan (I assume the other Tan/Blue goes to the Oil Reservoir?) The noise occurs when these two wires are touching. When they are disconnected, the continuous buzz as well as the ignition beep no longer sound.

(To be clear, the Oil Reservoir is about half full, and I know that is a "beep beep beep" not a continuous tone.)

Assuming this means the under console alarm/wiring is the real culprit...what say you electrical wizards???

Thanks in advance.
Dan

 

[wn6ngp]

the switch in the oil tank is a common failure. If you disconnect the wire at the oil tank does the beep go away. If it does then you have the answer. The problem is the switch in the oil tank.

 

[electricjohn]

Sounds like the oil tank level warning. Pretty sure you would have to replace the whole tank as I think the sensor is built in. I do not recommend running without sensor connected, as I came close to running without oil once.

 

[Texasmark]

Disconnect your warning module....Port side of the engine, to the rear of the oil tank and just above the lower cowling...cowling where the top cover rests. You said the oil goes 0101010 and I know that the temp is a solid 0.

The warning horn is activated by switched 12v from the ignition switch being on on one terminal and a ground on the other, coming from the engine on the tan/lt blue striped wire....in the 8 pin engine to remote connector. The Tan OT wire shorts to ground with a failure and the oil sensor shorts internally when the oil is low sending on 2 blue wires that short to the Warning module. It in turn produces a modulated ground connection for the horn. With the funny noises I'd say something is wrong with it. Without a warning module the oil goes directly to ground and the low side of the horn and is a solid 0. Without the module, in later engines, the two blue wires are connected to ground and the tan/blue stripe mentioned in the remote connection and the alert is a solid beep.