Gaffrig Tach bouncing at high RPM
 

All,

My starboard tach is bouncing around a lot. I think it is doing it even at 3000 rpm, but definitely higher. The only time it isn't bouncing is at idle. Port side tach is fine. The engine definitely isn't doing what the tach says.

I checked that all the wires are tight on it today. I plan to hook another analog tach to it next weekend and see what it does. I was a little surprised to see that every connector on the back of the tach has two wires on it. I would have thought that the wire that carries the signal would only go to the tach and no where else. The port tach has one connector on it with one wire, the rest have two.

Any ideas what could be causing the tach to be all wacky? :(

Thanks,
Garrett

Re: Gaffrig Tach bouncing at high RPM
 

Swap the wires between the tachs and try agina. That way you can tell if it's the tach or the sender. It's probably the tach.

Re: Gaffrig Tach bouncing at high RPM
 

More then likely you have a bad ground somewhere...i'm guessing on the engine causing the tach bounce.....check those first....i'd take each one off and make sure you have good contact. Also depending on how old you tach is theres a small circut board i have gotten in the past to cure this from Livorsi....(I'm assuming this is a Gaffrig/Livorsi Tach and not the Gaffrig of today) Just call them up and ask about it....i got one for free last time :)

Re: Gaffrig Tach bouncing at high RPM
 

Check the big connector from the boat harness to the engine harness. The big 11-pin pigtail at the rear starboard side of the engine. I had a similar problem with a tach on my 382, until it quit working completely. Checked the connector and found bad contact. Cleaned it out, applied di-electric grease and SHAZAM!!! Cared the problem.

Re: Gaffrig Tach bouncing at high RPM
 

Thanks Gentlemen! I have an email in to Gaffrig and I'll check out the connector on Saturday.
G.

Re: Gaffrig Tach bouncing at high RPM
 

Hey RedDog,

I pulled the big round connector off the back of the engine and checked it. It was fine. Stuffed with grease and no corrosion. It only had 9 pins though. It was about the size of a 7 way trailer plug. Is this the one you are talking about???

I hooked another tach up to the engine at the lake. It went bonkers too. I should have tried disconnecting the gaffrig with the test tach on there but I didn't, so I might try it again.

I'll check for ground issues on the engine. I'm also wondering if maybe I have a bad coil or other electrical issue on the engine.

Any other ideas?

Gaffrig doesn't have the parts any more for this tach. They said they would help me out though. I don't think the tach is the problem now that I've tested it some more.

Thanks,
Garrett

Re: Gaffrig Tach bouncing at high RPM
 

Thanks Troutly, I'll check it out.

Re: Gaffrig Tach bouncing at high RPM
 

If you have the tachs with built in hour meters,throw them away my gaffrig tachs were jumping around then not working at all,water intrusion.When I took out the guages brown dirty water came out.Replace with Lavorsi.

Re: Gaffrig Tach bouncing at high RPM
 

I'm going to do a couple more tests before condemning the tach itself. Unfortunately, my day job is going to get in the way this weekend. Playing on the boat is going to have to wait.

Garrett

Re: Gaffrig Tach bouncing at high RPM
 

Agree with Troutly onn this one, have also heard of the same. Try alligator clips and jumpe to ground the distributor and see if that fixes it.