1998 Mariner 150 OPTI #0G655960. Last June was getting alarm and no power. Connected to MEDS diagnostics and showed TPI codes about 90 times each. Both would sweep but while idling, the #2 TPI would jump about a volt. I ordered both TPIs and one did not arrive until Oct. I installed both and cleared codes and all seemed ok running in tank. No more fluctuations and codes not resetting. Boat sit from then til Feb and first time out was doing same thing. Checked codes again and had same TPI codes. While monitoring guage sweeps the #1 will stay on about 5 volts and never move and #2 will move from about.48 volts to about 5 volts. I checked wiring and terminal A is ground, B goes to ECU and C is 5 volts and when I unplug sensor it goes to 0 on guage so I assumed it was a bad #1 TPI. Installed a new one is still same. Something else strange is it will store an active TPI 2 code even though that sensor appears to be operting correctly. I have Mercury manuals but they do not show what I should be seeing at connectors or terminals. Is there a manual for Optimax diagnostics that might help me. I only saw a 90-889525 that says for 2000 model year and up. I think 1998 and 1999 might be only years with dual TPIs. Thanks for any info.