Where's the Tach????

[wolfscott]

Ok, folks, here's one for you. I have a early 70's model alpha one Mercruiser 165. It is a standard inline six. Now, here's where the fun begins. The tach does not work. So, me being the inquisitive one followed the wire from the tach to the back of the boat. And attached to the other end is.......???????? Nothing. Yep, thats right. Just a dead end. Now I have searched this engine over several times, and perhaps it is me, or perhaps it it just doesn't exist, but if it did, where would this be I ask. I have located all of the other dash related items. Water temp sensor? Check. Oil Pressure sender? Check. Volt meter? Check. Fuel sending unit? Check. But I will be danged if I can't find that one. I thought it was located near the front of the engine by the crank or cam shaft pulley's but I don't see it. Anybody out there have a idea where this is? That's one I really need. Thanks a bunch. Scratching my head in Vegas.

 

[mkast]

Re: Where's the Tach????

Negative side of the coil.
Although, the tachometer may be disconnected because the tachometer is bad.
If it is, an it's connected to the coil, the engine won't start.

 

[ziggy]

Re: Where's the Tach????

i think the tach wire (brown) connects to the (-) side of the coil.

 

[HT32BSX115]

Re: Where's the Tach????

Howdy,


Keep in mind that the the "PLUS" side of the coil in a points type ignition system is simply connected to 12v DC (or possibly through a resistor) any time the engine is running.

The negative side of the coil goes to the points/condenser.......(and the tach!)

The Tach is, for all practical purposes, a "pulse-counter" with an analog display("clock-face" meter).

If the tach is internally shorted as indicated above, the engine WILL NOT run. If it's otherwise defective, it of course will not work but the engine will run........

Also be sure to check the wire that goes from the negative lead to the tach, it may be frayed somewhere between the coil and the tach and is "shorting" out somewhere along the way.......

You'll may also be replacing the tach.

Most marine supply places (like WestMarine etc) have them.

You could also pick one up from Ebay.....



Regards,


Rick

 

[wolfscott]

Re: Where's the Tach????

Awesome!! Thanks for the info. I will check this out this afternoon. The end of the brown wire coming from the tach has a blue wire connector on it so quite possibly the wires may have come apart. Just to be sure we are on the same page, the coil has the single "spark plug" looking wire that plugs into the top right? About the size of a red bull can, and mounts on the side of the block right near the distributer?

 

[HT32BSX115]

Re: Where's the Tach????

Just to be sure we are on the same page, the coil has the single "spark plug" looking wire that plugs into the top right? About the size of a red bull can, and mounts on the side of the block right near the distributer?

Um.......... you might want to get with someone that has had their hands on an internal combustion engine at one time or another before you proceed.........

 

[wolfscott]

Re: Where's the Tach????

That was pretty bad huh? Actually I do all of my own mechanic work, up to and including complete engine rebuilds. So, if I offended any one, I am sorry. I just didn't know where the tach on a marine engine connected. But perhaps you or someone could give me some insight. The person who had this boat before me had taken the power wire from the battery and connected two wires , both red, to it and ran one to the solenoid, and the other to the starter. The two coming off have fused together from the heat. Wouldn't it be better off to run one continuous wire to the solenoid, and then one to the starter? The whole electrical things confuses me a bit. And again, I apologize for the earlier post. I love the reply though. That was funny.

 

[HT32BSX115]

Re: Where's the Tach????

Well, I wasn't trying to be funny nor was I trying to insult you. If I did please accept my apology!


You should get yourself an OEM service manual for your engine model/series. There's also many sources, wiki's etc on the net that you can reference on how a points type ignition system works.

I don't think any of us here can safely direct you through a "re-wire" process via "text-messages".

Most all of us just want you to get it right and not set yourself up for a possible electrical fire.

 

[wolfscott]

Re: Where's the Tach????

HT, I appreciate your candor sir, and I am not offended. The last thing I want with the kids aboard or anyone for that matter is a fire. I have an OEM manual that came with the boat, but unfortunately some of the sections are missing, that being one of them. I have done some research on the points type ignition system, and I think I have a pretty good handle on it. I want to do this job right. Having been in the navy, I know the dangers of fire aboard a boat, and we don't need that. Thank you for the post, and the advice.

 

[HT32BSX115]

Re: Where's the Tach????

The last thing I want with the kids aboard or anyone for that matter is a fire.

Me too!!


There may be someone here that'll jump in with a PDF manual you can download....we used to have them here but they got pulled.........

There's also a LOT of info on the net on points type ignition systems......


Regards,


Rick

 

[wolfscott]

Re: Where's the Tach????

Thanks Bubba, that's exactly what I have. The needle on the tach is stuck at 3 ticks off zero, and there is a brown wire coming off the neg side of the coil which looks as if it were cut, so I am guessing the tach is shorted out. As was stated earlier if the tach is shorted out, the engine will not run. I am going to run a temporary jumper between the two for verification. If it doesn't start, then it looks as if I am buying a tach.

 

[Fishermark]

Re: Where's the Tach????

there is a brown wire coming off the neg side of the coil which looks as if it were cut,

There should be three wires on the negative side of the coil:
1. To the points (distributor).
2. To the shift interrupt switch.
3. To the tach.

Here's a pic that shows the wiring diagram. (If it is too big, here is a direct link: Click here to see it online.)

 

[wolfscott]

Re: Where's the Tach????

Thanks for the diagram Fisher. That helps alot. I have looked at alot of diagrams, but most were generic. This one helps being specific to 160 and 165 mercs. Wish me luck boys.

 

[wolfscott]

Re: Where's the Tach????

Ok guys. I followed the wiring all the way to the coil. The stubbed wire was from the blower which was removed. The wire from the tach to the coil is intact. So???? My tach is stuck at 900 rpms, and the engine runs fine. Obviously the tach is not shorted. Is it possible to have these things repaired or is it not worth the trouble? Also the wiring from the batt to the solanoid to the starter has been replaced. It looks a lot safer now. Any ideas on the tach?

 

[Bondo]

Re: Where's the Tach????

Any ideas on the tach?

Ayuh,... Replace it...

 

[HT32BSX115]

Re: Where's the Tach????

Ok guys. I followed the wiring all the way to the coil. The stubbed wire was from the blower which was removed. The wire from the tach to the coil is intact. So???? My tach is stuck at 900 rpms, and the engine runs fine. Obviously the tach is not shorted. Is it possible to have these things repaired or is it not worth the trouble? Also the wiring from the batt to the solanoid to the starter has been replaced. It looks a lot safer now. Any ideas on the tach?

Yeah. Just pick one up at West Marine in Henderson

 

[wolfscott]

Re: Where's the Tach????

Pretty much what I was thinking. Thanks guys.

 

[L8-Again]

Re: Where's the Tach????

The stubbed wire was from the blower which was removed.

I hope I misread this and that you still have a FUNCTIONING blower motor still installed.

Just don't want anyone to get hurt!

 

[wolfscott]

Re: Where's the Tach????

No sir, there is no blower. It was removed prior to my buying the boat. I have run the boat a few times on lake mead, but rest assured with the cover open to fresh air. No worries. There will be a blower installed before the next trip out though. Thank you for your concern.

 

[wolfscott]

Re: Where's the Tach????

Ok, this is cool. I went to a couple of local junkyards here in Vegas. And as we are walking around, the boy comes running up and says, hey Dad, there's a boat over here. And sure enough, there was a POS cuddy, all beat to heck, with a few miscellaneous items I needed. Say what?? He found a boat in an automotive junkyard? Yes I did. And the two most needed items? Yep, there they were. A blower, and a new bilge pump. Sweet. And, we gutted about 30 feet of wire from this thing. Even better score. So, the result of all of this you ask? The boat known as Wolf Run is back in the water, and Bad Fast folks.