Be very cautious of how much $$ you put into this outboard. As Fitz said, there were many flaws in these engines, but the problems could be hit or miss and some of them were okay. The fact that yours is 25 years old and still running means you got one that was okay to start with. As for your current problem, what is the engine doing/not doing?
Have you tested the TPS or just read the code? These were a 3-wire sensor which means you have a ground, 5 volt reference, and signal. Just do an internet search for "how to test a 3 wire throttle position sensor" and you'll find plenty of information. In short, you need to ensure you have good 5 volt power at the sensor and when the throttle plate moves from closed to wide open the sensor shows smooth, consistent voltage changes from about 0.5 volt to 4.5 volt on the signal wire. If your voltage on the signal wire is jerky or jumps wildly at any point the sensor is bad.
If you don't have 5 volts at the sensor, check the wiring harness to make sure the ground wire reads 0 ohm to a block ground location. Next, make sure the 5V power wire has 5 volts to a block ground. If either of those fails you probably have a bad EMM because the ground to the sensor and the 5volt reference were both delivered through the EMM. You can have the EMM repaired (about $500 +), but this is the point where you ask yourself if you want to put more money into an outboard that is increasingly difficult to repair due to parts being unavailable and shops not wanting to touch them.
The TPS is no longer available new, but can find good used ones on Ebay or call around to shops selling used outboard parts.
