Re: Tach question
You say the boat is powereed by a 150 Merc (singular) yet you say "tachs" (plural) jump around and only the fuel gauge works. If the speedo doesn't work it is not electrical as that instrument is non-electrical except for the internal light. Check for a plugged pitot or kinked hose going to the back of the speedo. Gauges jump around generally because of loose wires. The quick check would be to look at them and tighten the connections. Gauges need +12 volts and ground and a functioning sender in order to work. Those are all electrical so yes -- there is a good chance the problem is electrical. So what gauges do you have that don't work and when and how did the problem first appear?
