'96 Mercury 225 alarms flashing and buzzing

[Champion88]

Serial number 0G407403
At first motor was getting the oil/water lights flashing intermittantly but the buzzer wasn't working, and the motor would slow to 3000 rpm. We installed a new water pump and thermostats and new alarm buzzer, but was still getting the alarms and now the intermittant beeps. Checked the TPS sensor and wasn't getting the correct reading at full throttle, replaced it to only find out the hot foot needed adjusted because we weren't getting full throttle. Now... sometimes start it up and run full throttle with no alarms, next time soon as we start it the oil and water lights are alternating flashing and getting the intermittant beeps. Could water in the separator cause this? We have about 5psi water pressure at idle and about 12psi at full throttle on the new pressure guage we just installed. We thought it was the float sensor in the onboard oil tank so we unplugged it to see and the alarm stopped, but came on again later. The oil tank is full.
What else could cause this? Those are the two things the service manual suggests can cause this, any ideas on what else it could be?
Motor runs perfect at all rpms, even when the alarms are going off.
Also what is the minimum PSI for the water at WOT, I thought it was 12, correct?

[Champion88]

The water pump wasn't really bad when we replaced it either, but I suspect he was overtrimming when he wasn't getting full throttle and loosing water pressure to make it hot. And his water pressure guage was faulty and he didn't realize it, it wasn't going to zero with the motor off that's when we installed a new one.

[EuropeanAM]

1. Water pressure specs are: 1-3 psi at idle, 8-12 psi @ WOT (MINIMUMS).

2. Dump contents of water separating filter into a glass jar to inspect for water separating out at bottom of jar. Water in fuel WILL cause this warning.

3. You probably made a mistake altering the throttle/TPS setup. There was a service bulletin back then which specified a lower TPS setting on lighter/faster setups (specifically with models that utilized the smaller-bore exhaust tuner).

[Champion88]

Thanks Don, I have been suspecting he might have water in that filter since the alarms were so hit and miss.
I didn't alter the TPS settings, the voltage in neutral was .95 and that's what I put it back at per the service manual. We just weren't getting the correct voltage at WOT and after I installed the new one it had the same WOT voltage that's when I figured out it wasn't getting all the throttle it should be getting.

[EuropeanAM]

It's the WOT voltage that may have been INTENTIALLY altered, per a service bulletin from that vintage.

See how it does at WOT.... if you find that dropping the hotfoot back to 7/8 throttle results in HIGHER RPM's than WOT, it may need to be reverted back to the previous settings.

[Champion88]

Just the opposite, the motor was slow out of the hole and no power on top end, now it screams out of the hole and absolutely flys on top end.

[Champion88]

Don, if we find water in the filter then it should be replace correct, not just dumped out?

[EuropeanAM]

Correct. REPLACE filter if water laden.

Also, if water is present, you need to determne if there's WATER in the fuel tank (via pumping the tank COMPLETELY DRY, and starting with a FRESH load of fuel).

[Champion88]

Thanks!!

[Champion88]

Don, we dumped out the contents of the filter in a glass jar and it looked perfectly clean, no water at all. But the next time we took it out we didn't get the flashing alarms. I ordered a new filter, but it hasn't arrived yet.
I have installed a new sensor in the top of the oil tank on the motor, and after I turn on the key and wait about 30 seconds the oil light will come on. If I unplug this sensor we never get the light.
Is there something special I need to do when installing this? It has the plastic split sleeve in there, and I just pulled the old one out and put the new one in and plugged in the two wires. They don't matter which wire goes black and which one goes on the blue, right? Also there isn't supposed to be oil in the hole correct?
This sensor just seems to be my problem, but I can't figure out why the new one didn't fix it.

[EuropeanAM]

There should be no oil in the sensor opening.

More than likely.... it was not the sensor. There is a FLOAT inside the tank (with a magnet on it that interacts with the sensor to send a signal).

The float (or tank) can swell, and prevent the float from moving properly. If you've confirmed the tank is 100% full with ABSOLUTELY no air space present.... you'll likely want to replace the entire tank assembly.

[Champion88]

Yep it's full,soon as I start loosening the cap it starts running out.
So that's how that sensor works.
Thanks Don for all your help!!