4BT Tach issues

[Blair Ostergren]

I am having problems with my port tachs. I bought the boat with this issue so I cannot provide previous info. The lower helm tach was pegged at 4k with or with out motor running. Nothing on the upper helm. I removed the upper helm tach and installed in lower station, nothing. I put the starboard tach connection on it and tach worked. now I know I have a working tach at lower port station. I have a signal generator at the fly wheel. I disconnected and cleaned the connection. I am guessing that the signal generator may be bad. How can I test to make sure it is producing signal at the flywheel and check signal at the tach? Should I be looking somewhere else? Is there a magnet on the fly wheel that produces the signal? I

Thanks,
Blair

Topic

[john]

Swap the sender is the easiest way test it. If it duplicates you haveyour answer

[Blair Ostergren]

I don’t think I am confusing things

1. (The Problem ) The port side does not have any tachs working upper or lower.

2. Part of my trouble shooting I tested a port tach to make sure I have at least one good tach. This would eliminate the problem being I just have 2 bad tachs. I did this by using starboard engine wire at dash.

3. Yes, I have one Signal generator at flywheel housing that operates both tachs.

4. ( The Question) How can I test the signal generator at the Flywheel to make sure it is producing signal?
Sender part # 3078155 there are two ends one is plugged and the other is plugged into engine harness.
-there are two wires being used from the sender. should I assume one is power going to the sender and the other is signal going to the tach?

5. one more problem I am dealing with, when the port engine is running the buzzer does not shut off. I and tracking that next. I thought that was from oil pressure sender. would the tach have anything to do with buzzer? and yes engine has oil pressure and reads so on the gauge.

[john]

If you get a tach to work on port and starboard your senders are good. Lower and upper helm will share the same sender. I would look at wiring, corrosion, grounds

[Blair Ostergren]

Here is where I am at the moment

lower port helm tach is a good tach, I verified this by attaching the lead from starboard engine and it worked fine. I did this because the lower port tach I removed had the needle pegged at 4k with or with out power to it. So I wanted to make sure I have a working tach at lower port helm. While testing I went to fly bridge and the starboard tach worked with starboard engine even though I had switched the leads at lower helm (port lead to starboard tach and vis versa) I was checking to see if the upper and lower helm shared a signal or had independent signals from the motor. With everything hooked up back the way it is supposed to be (except I have no tach installed at upper port helm) the port is not working.

my next step is to try and test to see if the signal generator is producing a signal and check the signal input line at the helm. (other suggestions appreciated)

My question is how do you test that signal ?

More info
1. I bought the boat with this problem so have no prior info and cant get it.
2. Engines did get wet, and I have checked and cleaned connections
3. 4BT serial # 45294155
4. Part number for the signal generator on flywheel housing 3078155

[Rob Schepis]

If you moved the starboard tachometer to the port side and it worked didn’t that prove that the port signal is there?

[Author]

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