Help please I need a good Yamaha mechanic advice

[BayouNola]

I hope someone can please answer my problem. I have a 1994 150hp yamaha. I recently bought this boat and had an issue where the alarm would go off as soon as i would give the gas. At that time I changed the water pump and the thermostats. It seem to help until this weekend when my solenoid on the up trim went out with my battery. I bought a new battery and launched. As soon as I reached 1500 rpms the alarm would go off and the oil and heat symbol lite up on the tach. The tach has visual condensation thur the glass. After riding for a few minutes I turned the motor off and when I tried to start up I had nothing like the battery was dead. About 10 minutes went by and it started up and again the alarm went off after 2100 rpms. I went ahead and put the boat on the trailer and tried to lift the motor with the trim buttons and nothing like the battery was dead? ??? I had a mechanic look everything over and the oil levels were good and the motor was peeing strong and cool. He thinks it could be a faulty tach giving a false alarm. Is this possible and what else can I do. Thanks and PLEASE HELP.

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[rodbolt17]

find a real mechanic.
toss the tach in an EPA approved dump site and it wont affect alarms.
low battery voltage at the ECU will set an alarm.

[madharchod]

nobody sells cheap stuff only if they have faults that will cost a lot to fix and in your case it just looks like that ,but i would suggest you go through your wiring and connections as this could be the problem as if the battery sounds dead and come back alive its definitely the connection
where-I dont know
but its wise to trace all your wires and connections
1994 engine bound to have corrosion problem as that time Yamaha didn't invent the anti corrosion devices which are there in later models