Tachometer

[SereneWarrior]

I have a 1970 53 MY with DD 8V71Ns. My question is about instrumentation, specifically tachometers and whether or not the RPM reading can be adjusted. My port tach on the salon console clearly registrers 100-300 RPMs low compared to the one on the flybridge, dependant on engine speed. At idle, the difference is 100 RPMs. At WOT, the difference is 300 RPMs. The starboard engine tachs agree almost exactly throughout the RPM range.

Can the tachs be adjusted or must I replace the port engine main console tach?

[Trojan]

There is an adjustment screw on the bottom of the tach inside. Accessible through a small hole in the bottom. You can adjust it, but I don't think you will win. Give it a try. You have nothing to loose. I didn't win. My starboard tach is correct sometimes. The longer I run the engine the more accurate it gets. I use a synchronizer and forget about it.



BILL

[SereneWarrior]

Trojan, thanks I'll give it a try. Also have a Glendinning, but it is in disrepair. I don't know much about them, but have looked at the website. Suspect I have a bad synchro. Wires were disconnected when I bought the boat and I haven't got around to fixing the thing. Perhaps it's time....

[RyanN]

Today while running our boat, our port side tachometer stopped working. We were running at 1800RPM or so, and I noticed that the port tach went to 0 while running. I also checked the tachometer inside and it also read 0. The synchronizer still works perfectly though. I don't know anything about tachometers or how they work. I'm looking for someone who may know exactly what is wrong. Any ideas of where to start before I tear up half the boat looking for something as simple as a loose wire or something?

[TopHattandTails]

Mine was the port tach... Stop using the synchro if you have the same problem. I had the port side tach wire out of the engine (charging pump, I think) pulled and the tach wire rebuilt (actually the worm gear on the motor). The tach has a square end on the engine and rounded out the plastic connection. You can buy new - but why. Just rebuild it. Took my mechanic less than 2 hours to dissassemble, rebuild, reinstall.

[wshelton]

Okay since we on the issue of tachometers this is my problem.

As usual while fixing one problem I create an additional one.

I have DD 671N and Guest Judson Syncronizers that just to let you know when the engines are in sync.

I apparently broke one off the Starboad engine and now no tach. signal.

Guest is out of business and no help.

This piece attaches to the back of the engine and has a green wire attached to the outside of this piece and two other wires, one red and one yellow coming out of a wireing harness on the engine attached to the top of this device that has a red rubber cap one the top convering the yellow and red wires. (Exact piece on the other engine)

I need this replace this whole piece.

Other question is how can I at least make the tach. work?