will this Quicksilver tach work on my motor? It looks the same but my manual doesn't give me a model # for the replacement. Will a 65794A2/73370A2 work, or should I look for a different aftermarket tach? Thanks!
I should probably also mention that this is a Thunderbolt Ignition model. I've read several threads on here about people having a hard time getting the correct tachometer for a thunderbolt ignition. Is there something special I have to look for?
I just tried to look up the part number on mercury parts express.com. It is no longer available. For the price of the tach on ebay , you can get a Teleflex or Faria here at iboats.com. They come with complete instructions on how to install.
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"Many of the greatest sailors were pukers."--Thorfinn Skullsplitter
Scott, That motor will work with all the aftermarket universal tachometers. In 1973, merc made unique tachs that ran off the switchbox pulses. They wired their motors to use these unique tachs. The one on e-Bay may be that type, but I do not know for sure. However, you may easily convert your motor to run off the aftermarket tach instead.
When the older mercs came from the factory the brown wire (tach signal) was connected to the switchbox on the motor. If you move the brown wire to either of the AC connections of the rectifier, the aftermarket tach will work. Set it to 6P.
Chris, are you saying he should just disconnect the brown wire from the switchbox and move it over to either AC side of the rectifier? So in other words that brown wire has no other function than carrying motor impulses from the switchbox to the tach?
Thanks for the responses guys, I decided to go for the aftermarket tach. I see the brown wire on the switchbox and I see both of the yellow/red wires on the rectifier, but the brown cable coming from the distributor isn't long enough to make it to the rectifier on the other side of the engine. What should I do?
Ahh, so the brown wire that runs from the engine harness? Disconnect from the switchbox and run to the rect? I'll run outside and check out the motor and report back.
Got her all hooked up and I'm on my way to the lake to try it out in half an hour. Just to verify, the AC side of the rect is the yellow/red wire(s), not the solid red wire, correct?
yes, the 2 yellow/red wires run to the stator. you want to double up the brown wire on either one of the contacts where the yellow/red wires hook up to the rectifier.
Took it out on the lake today and it was a no go.. I think my problem is that I don't have a wire running to the IGN post on the tach. My old quicksilver tach the black wire running to NEG, the brown running to POS and another wire briging POS to the mounting bracket, and a white wire running to the light. What wire should I be running to IGN? It says 12-16 volts, can this be any 12 volt wire (take a tap off my CD player?) or does it need to run to the control box so the tach knows when to turn off and not drain my battery? I'd really appreciate a shove in the right direction, you guys have been awesome so far.
I tracked down the white wire and apparently it ran to the backlight of my old quicksilver tach. I'm leaving for radio shack to buy another ring terminal so I can chop the wire and reattach to the tach. I'll post back with results.
She's alive!! One problem though, it's not reading the correct RPMs. At WOT It's only reading about 3600 when I know I'm going about 5200. The Teleflex Manual says to set the thing to 4P and everyone else tells me 6P. How can I tell how many poles are on my alternator?
Looks like the back of the tach was already set at 6P. The voltage regulator is also brand new installed at the dealer and the battery is getting a good charge. What else could it be? Could the previous owner have installed a different size alternator?
I just had the boat out on the river with my marine mechanic about a week ago and he hooked up his marine tach and it read 5200. The boat hasn't changed performance wise, and it rips on to plane in a couple seconds. I don't see any way the motor could turn an extra 1600 RPM.
The response I got from Teleflex was to try setting it to 5p or 4p and see if I could match the tach to actual RPMs. Is there a logical reason why another setting would be accurate?
Scott, Unless your Stator is bad or an incorrect model(and I do not even know if that is possible), 6P should be the setting. Sounds like the techs were grasping at straws.....
Hmmm... The dealer said the Stator was checked and found to be good, wouldn't a bad stator also give me some engine trouble? Is there really nothing else that this could be? Should I resort to exchanging the tach for another at the store?
1973 Mercury 850 85HP correct Tachometer?
Re: 1973 Mercury 850 85HP correct Tachometer?
Re: 1973 Mercury 850 85HP correct Tachometer?
Linear Mode
