Diagnosing SportJet 175 Sensors Issues

[jrastama]

I'm working on a used Sugar Sand Mirage 1800 we bought. It has the Mercury SportJet 175 in it. As I dig deeper into the boat, I've uncovered some issues I'm trying to fix / diagnose. I found that the alarm buzzer had been intentionally disconnected. I reconnected it and I now get the diagnostic single beep when I turn the key to the on position. So that's a start. Next, I want to confirm that the three sensors are working... according to the user manual for this engine it has three sensors: Oil Level, Oil Motion, and Engine Temperature. I want to test them all and fix, if needed, to get all three working as they should be.

The easiest one to test should be the Oil Level as its a simple float sensor in the oil reserve tank. With the key in the on position, I remove that cap so that the float drops completely and there is no alarm. I replaced that sensor, and still no alarm sounds. So, I tried grounding the blue wire that goes to the ECM and still no alarm. I swapped out the ECM with another used ECM and still no alarm. As I see it, next step may be to try to tap into that wire very close to the ECM to see if its an issue with that wire. After that, I guess I'd probably need to purchase a new ECM... but wondering if I'm diagnosing this correctly.

As for the Oil Motion sensor, I don't understand where that is. Or possibly it's been removed? Attached are a few pictures of the oil pump. I don't see a single electrical wire connected to it. Am I overlooking it or any ideas what's going on here?

Finally, regarding the engine temp sensor, I see some three tan with black stripe wires coming from the temp sender in the starboard side cylinder head, one has a label on it that indicates temp sensor. But on the port side cylinder head in that same spot there is a single tan with green stripe wire. So I'm not quite sure which wire to ground to test the temp sensor.

Any suggestions would be greatly appreciated. The engine user manual I have unfortunately does not include diagnostic info for the sensors.

 

[Bilmon]

I'm working on a used Sugar Sand Mirage 1800 we bought. It has the Mercury SportJet 175 in it. As I dig deeper into the boat, I've uncovered some issues I'm trying to fix / diagnose. I found that the alarm buzzer had been intentionally disconnected. I reconnected it and I now get the diagnostic single beep when I turn the key to the on position. So that's a start. Next, I want to confirm that the three sensors are working... according to the user manual for this engine it has three sensors: Oil Level, Oil Motion, and Engine Temperature. I want to test them all and fix, if needed, to get all three working as they should be.

The easiest one to test should be the Oil Level as its a simple float sensor in the oil reserve tank. With the key in the on position, I remove that cap so that the float drops completely and there is no alarm. I replaced that sensor, and still no alarm sounds. So, I tried grounding the blue wire that goes to the ECM and still no alarm. I swapped out the ECM with another used ECM and still no alarm. As I see it, next step may be to try to tap into that wire very close to the ECM to see if its an issue with that wire. After that, I guess I'd probably need to purchase a new ECM... but wondering if I'm diagnosing this correctly.

As for the Oil Motion sensor, I don't understand where that is. Or possibly it's been removed? Attached are a few pictures of the oil pump. I don't see a single electrical wire connected to it. Am I overlooking it or any ideas what's going on here?

Finally, regarding the engine temp sensor, I see some three tan with black stripe wires coming from the temp sender in the starboard side cylinder head, one has a label on it that indicates temp sensor. But on the port side cylinder head in that same spot there is a single tan with green stripe wire. So I'm not quite sure which wire to ground to test the temp sensor.

Any suggestions would be greatly appreciated. The engine user manual I have unfortunately does not include diagnostic info for the sensors.

Not very familiar with the 175 but it looks like the motion sensor is on the oil pump. Is it possible a prior owner disabled the pump and was running 50:1 premix? Real common as the early 175's were prone to pump gear failure and a lot of people have disabled them and gone to premix though I believe the problem was with the late 90's motors and corrected sometime soon after. If you are on facebook there is a Sugar Sand Boats and a Merc Sport Jet group that might be of some assist, the Mercury service manuals can be found there

 

[jrastama]

Thanks. I'll try to find that Facebook group to check there as well.

Digging for the motion sensor, I think it's part # 12430A4 and it appears to only be on the older versions of this motor:

https://www.boats.net/catalog/mercury-sportjet/jet-drive/175hp/175xr2-sportjet-jet-drive-powerhead-0e151580-thru-0e369299/oil-injection-components

And not on the newer version that I have:

https://www.boats.net/catalog/mercury-sportjet/jet-drive/175hp/175xr2-jet-drive-pump-0e369300-thru-0e433153/oil-injection-components

Looking at my service manual, I have 90-852396 but looks like 90-852396R1 is for the newer versions so I'm going to try to get my hands on 90-852396R1 and see if that confirms that there is no motion sensor for this version of the motor.

Beyond that, I still need to figure out how to test the oil level sensor and the engine temp sensor.

 

[jrastama]

Thanks. I'll try to find that Facebook group to check there as well.

Digging for the motion sensor, I think it's part # 12430A4 and it appears to only be on the older versions of this motor:

https://www.boats.net/catalog/mercury-sportjet/jet-drive/175hp/175xr2-sportjet-jet-drive-powerhead-0e151580-thru-0e369299/oil-injection-components

And not on the newer version that I have:

https://www.boats.net/catalog/mercury-sportjet/jet-drive/175hp/175xr2-jet-drive-pump-0e369300-thru-0e433153/oil-injection-components

Looking at my service manual, I have 90-852396 but looks like 90-852396R1 is for the newer versions so I'm going to try to get my hands on 90-852396R1 and see if that confirms that there is no motion sensor for this version of the motor.

Beyond that, I still need to figure out how to test the oil level sensor and the engine temp sensor.

Hmmm... even 90-852396R1 shows the motion sensor. This motor has definitely not been changed to premix. So possibly they just removed the motion sensor for some reason. I'm looking further into that next.

 

[jrastama]

Hmmm... even 90-852396R1 shows the motion sensor. This motor has definitely not been changed to premix. So possibly they just removed the motion sensor for some reason. I'm looking further into that next.

Now I'm thinking at some point with these motors they may have got rid of the motion sensor... there is supposed to be a slot for the sensor behind the oil pump but it looks to me like there is no longer such a slot as per the attached image.