The NY Dad
Member
I had the boat out by myself the other day and opened it up. I got 52MPH at about 5200rpm, I know marine speedos are notorious for not reading correctly, but what concerned me is the tach. The markings leave plenty to be desired on the OEM tach, only marked every thousand rpm, so I'm guessing at the 5200 rpm by looking at the needle position. I know the motor could not be running at 5200rpm because the rev limiter on my motor is set for 4950 rpm, 4400-4800 is where it should be WOT. So It's off by at least 250rpm. I would say it's off by 350 rpm or more because I don't think the engine was turning 4,800 rpm it definitely didn't sound stressed at all.
Before I do anything I am going to find the switch on the back of the tach and move it back and forth a few times to clean the contacts then take the boat out and try it again.
I have read about using a frequency generator and one guy used a fluorescent bulb and a piece of tape on the belt pulley to calibrate the tach. These methods work but I do't want to mess with the math if I don't have to.
So I am thinking I will call Auto Zone see if they have an inductive timing light with rpm readout, I can borrow for an hour or so. Run the motor at 1,000rpm on the timing light readout, and compare the reading on the timing light to the reading on the boat tach,adjust if necessary, then repeat at 2,000, 3,000, then 4,000.
Does anyone know of a reason this wouldn't work.
Before I do anything I am going to find the switch on the back of the tach and move it back and forth a few times to clean the contacts then take the boat out and try it again.
I have read about using a frequency generator and one guy used a fluorescent bulb and a piece of tape on the belt pulley to calibrate the tach. These methods work but I do't want to mess with the math if I don't have to.
So I am thinking I will call Auto Zone see if they have an inductive timing light with rpm readout, I can borrow for an hour or so. Run the motor at 1,000rpm on the timing light readout, and compare the reading on the timing light to the reading on the boat tach,adjust if necessary, then repeat at 2,000, 3,000, then 4,000.
Does anyone know of a reason this wouldn't work.