How to 'hook' a shop tach to a 3.0L...?

[Rocky_Road]

I have a very accurate automotive shop tach...that I need to know how to use with a Mercruiser 3.0L (SN OWO39755).

I intend to set my idle speed, on the water...as outlined in the service manual.

The 'old' days, of clipping the tach to the negative post of the ignition coil...seem to be long gone!

 

[Don S]

Re: How to 'hook' a shop tach to a 3.0L...?

Good question, I've had a digital tach on my Snap on timing light with an inductive pickup, for so long (15 years) that I don't have any idea how you would on the new EST distributors. But let me look around, there must be a preferred way.

 

[JustJason]

Re: How to 'hook' a shop tach to a 3.0L...?

should have a grey lead coming off of the coil. You may find a bullet connector that you can grab on to, or carefully backprobe the connector and hook up your shop tach to that.

 

[JustJason]

Re: How to 'hook' a shop tach to a 3.0L...?

1 more thing....

The 'old' days, of clipping the tach to the negative post of the ignition coil...seem to be long gone!

Not really.... the post was just a way of attacting a wire to the coil. As in a termination spot for the wire. Now they just take that post and put it inside a plastic connector. Your really doing the same thing/process, just looking for that "negative pulse".

 

[Don S]

Re: How to 'hook' a shop tach to a 3.0L...?

Just found it, as Jason says, there should be a bullet connector in the gray wire.

NOTE 2: Gray lead for use with service tachometer.

carefully backprobe the connector and hook up your shop tach to that.

I hate doing that, it usually ruins any seal that was on the wire.

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[JustJason]

Re: How to 'hook' a shop tach to a 3.0L...?

I hate backprobing to. I have a few Fluke backprobes that came with one of my meters that work okay.
Then I found out about these.....

http://www.toolsource.com/backprobe-kit-p-96147.html?osCsid=q96gpbrjs8u71kog6bbhuioc56

They are made by thexton and work great. The ends are sharp like needles. With a little dialectric (or usually just spit ) they slide right through the rubber. They are real sharp though, so 1 has to take care not to pierce the wire.

 

[Rocky_Road]

Re: How to 'hook' a shop tach to a 3.0L...?

Nice work, Don and Jason!

If I read the both of you right, I use the red lead on the shop tach on the gray wire...and ground my black lead, as usual. If I can find the female 'bullet', I can make me a simple lead, with a male terminal.

Don...your description of your Snap On timing light got me interested. There are quite a few being sold on eBay...models 1261, and 2261. The pricing is all over the place! What model do you use...and do you have any idea as to the difference between the 1261 and the 2261 (Snap On's website is down for some reason)?

Also, Don...what do you think about this clamp on tach?
http://www.esitest.com/cart/325.html

 

[dan t.]

Re: How to 'hook' a shop tach to a 3.0L...?

for back probing I use "T" headed pins, found them at the local hobby supply store

 

[Don S]

Re: How to 'hook' a shop tach to a 3.0L...?

I have the 2261, I looked on ebay and the 1261 seems to be nothing more than an older model of the 2261. I do know there are other inductive pickup timing light brands out there that are just as accurate and also have the advance feature and the digital tach for a lot less money.

As far as that tach goes?? I have no idea, don't own one and don't do tool reviews and comparisons. Having said that, it would probably work fine. WIth the state of electronics today, it would be pleny accurate enough to check rpms with.

 

[chiefalen]

Re: How to 'hook' a shop tach to a 3.0L...?

60 bucks for that clamp on one is money well spent.

I was gonna post why not get one like that, my friend has one, was gonna ask the brand name and post it.

Then whenever your friends need to have you come over with it, ya drinking for free that day my friend. HA.

 

[Rocky_Road]

Re: How to 'hook' a shop tach to a 3.0L...?

Then whenever your friends need to have you come over with it, ya drinking for free that day my friend. HA.

I like your thinking, chief!

Only problem is...my friends know just how much 'free' beer that I can consume...and will realize that they will save a whole lot, buying their own tach!

Need to plan the First Annual BYOT party (bring your own tach)....

 

[chiefalen]

Re: How to 'hook' a shop tach to a 3.0L...?

That might even be the one he has. Between the four core guys i hang with that work on there own stuff we have almost everything for boats and auto stuff.

Just got done with a diesel hoe a guy got for almost nothing. I like diesels.

One guy bought the tach say, i got all the pullers, and a bunch of spare parts like alternators, and pulleys, starters also one or 2. Another guy is a master welder.

Other guy has a reader for cars, another guy got the hoists, and a bunch of tools, gotta say we almost got it all.

Or we fabricate it.

 

[Rocky_Road]

Re: How to 'hook' a shop tach to a 3.0L...?

I hate it when a person asks for help...gets great input...and then you never hear the results from the poster!

So...I am pleased to tell you (especially Don, and Jason) that the gray lead was right where I was told to look...and my 'vintage' shop tach worked perfectly, when connected!

On the muffs, my engine (3.0L) would idle at 740 rpm, in forward gear. I know that I am supposed to set the idle in the water...but there has to be a ballpark figure for this on the trailer?

Thank you for the great research on my tach question...!

 

[Don S]

Re: How to 'hook' a shop tach to a 3.0L...?

Glad you found it and it worked out. Hope you checked your onboard tach with your shop tach to see if it's reading ring.
I normally set a 3.0L engine in the 725 range. If everything is adjusted right, it will usually idle around the 650 mark in the water

 

[Rocky_Road]

Re: How to 'hook' a shop tach to a 3.0L...?

Glad you found it and it worked out. Hope you checked your onboard tach with your shop tach to see if it's reading ring.
I normally set a 3.0L engine in the 725 range. If everything is adjusted right, it will usually idle around the 650 mark in the water

The helm tach was within reason...but the graduations are so coarse, that it is useless for what I am trying to do. My shop tach has a 'low rpm' scale, and I can witness every 'hiccup' at idle. I plan to use it to adjust the idle mixture.

I just realized that I have a new question! Any reason why I can't adjust the idle mixture (2 bbl), on the muffs?

 

[Don S]

Re: How to 'hook' a shop tach to a 3.0L...?

You should be able to get it real close, I have to always adjust them out of the water. Then when you get to the water, you can always do some final tweeking.

 

[Rocky_Road]

Re: How to 'hook' a shop tach to a 3.0L...?

You should be able to get it real close, I have to always adjust them out of the water. Then when you get to the water, you can always do some final tweeking.

Great!

See you on the ebb tide...!