Need help engine swap from Carb’d 135 to Optimax 150

[Onequickwrench]

Hello all.

First time Mercury owner here.

recently purchased a 1999 Key West center console with a tired 1999 carbureted 2.0 135Hp motor.

a budy had a functional 1998 Optimax 150 off his 1998 Grady White left over from a recent repower.

I hung the 150 on the transom, hooked up the fuel line, oil lines, battery cables, and control cables inside of an hour. Checked the remote “whip” between the two boats - they were identical, so I attached the whip to the motor harness and hit the starter switch.

low and behold the engine started right up, but immediately started a consistent beep whenever the motor is running.

oil tank and oil pump are primed, even went through the priming procedure to insure the oil pump is working.

engine won’t rev past 3000 rpm, but will idle with no issues.

good water flow from “pisser” and cylinder doesn’t get that hot after running, so it’s not overheating.

Anyone have any ideas? I’d really like to make it out to the lake this weekend

 

[Chris1956]

Optimax's have several alarms. One of them is when the sensor detects water in the water separator.

You might tell us the number of beeps or solid tone length.

 

[Onequickwrench]

Thanks for the reply.

I’ve already drained the water separator and checked it again after priming the system - no significant water build up.

After the initial key on “beep” the system remains silent until the engine is running. A rhythmic on/off beep starts before the starter motor has quit spinning and continues until the key is turned off.

I’ve read through the service manual on the Optimax paying particular attention to the chart on what the “beeps” mean based on their frequency. The thing is, no where in the chart does it describe a steady on/off beep.

 

[Chris1956]

It is likely time to test the possible sources of the alarms. Test the water separator sensor to see if it is generating an alarm. Test overheat sensor, oil tank level sensor, etc. The Service Manual should help.

Does the motor alarm with the motor not running and the key in the on position?

 

[Onequickwrench]

It is likely time to test the possible sources of the alarms. Test the water separator sensor to see if it is generating an alarm. Test overheat sensor, oil tank level sensor, etc. The Service Manual should help.

Does the motor alarm with the motor not running and the key in the on position?

Im pretty sure the alarm would stop if the engine quit running, but since it idles beautifully I can’t test that theory. the only way to kill the engine is to turn off the key, which is supposed to reset the system.
There isn’t much in the service manual regarding the oil level sensor electrical values (resistance or continuity).
There’s a flow chart for diagnostic steps to take on the oil level sensor and my sensor readings fail it. Hard to imagine the sensor would work perfectly and then fail during the engine swap procedure