Assuming you have the 240 EFI engine-
There are several threads here about the infamous, crazy stupid expensive Merc TPS. I wrote some of them.
Let's back up a bit.
How are you connecting to the tps? There is a VOLTAGE SETTING procedure and a RESISTANCE TEST procedure.
For the voltage set: tps needs to be connected. You will need to disconnect the temp sensor on port side cylinder head. I recommend the test harness from Merc about $30. Makes the job easier. However, it can be done without it. With your meter set to 20V range, pierce center wire and one of the outside wires. Which outside wire? Pick one. Turn key on, engine off. Meter should show somewhere between upper & lower spec. Move throttle lever from idle to WOT. Meter should show smooth increase or decrease. If not smooth, Break Out Another Thou (BOAT). Also, pierce other outside wire and repeat. If meter changes smoothly both times, you dodged a bullet. To make your voltage adjustment, loosen 2 small screws that hold clamps that hold the tps. Rotate tps slightly until you can get your settings. WOT setting is more important than idle. Tighten 2 screws. Gently! Not very big. Reconnect temp sensor.
RESISTANCE TEST: is only to test the tps. Disconnect 3 wire harness. Set your meter to 10kΩ. Connect to center and one outside. Run throttle low to WOT. Same as before--need smooth transition. Swap outside wire and repeat.
