Mercruiser mechanical tach conversion

[Mguill4650]

I am restoring 1935 Dodge runabout and will be replacing the original engine with a Mercruiser 140 - serial number 0A432326/ 1985 - setup as an inboard. I would like to use the original mechanical tachometer. Is it possible to convert the Mercruiser electrical connections to run a mechanical tach? Distributor conversion kit?

Thanks

 

[Alumarine]

When you say mechanical tach do you mean one driven by a rotating cable like a speedometer cable?

 

[Bondo]

I am restoring 1935 Dodge runabout and will be replacing the original engine with a Mercruiser 140 - serial number 0A432326/ 1985 - setup as an inboard. I would like to use the original mechanical tachometer. Is it possible to convert the Mercruiser electrical connections to run a mechanical tach? Distributor conversion kit?

Thanks

Ayuh,...... Welcome Aboard,..... What are ya usin' for intake, 'n exhaust manifolds,..??

I've never seen, nor heard of any sorta mechanical tach that'll work on those motors,.....

 

[Mguill4650]

Yes, the original mechanical tach is driven by a cable.

 

[Mguill4650]

The intake will be handled by an add-on water pump such as a #777 and the discharge is attached to the exhaust pipe as was the original inboard engine.

 

[Mguill4650]

Does anyone have experience with the Cable X made by Abbott Industries used to convert a mechanical speedometer to an electric speedometer? I will check with Abbott next week - hoping it can be modified to convert my tach??

 

[Bondo]

The intake will be handled by an add-on water pump such as a #777 and the discharge is attached to the exhaust pipe as was the original inboard engine.

Ayuh,.... Aren't ya gonna run outa water, long before ya run outa gas,..??

Donno where you'd ever find 'em, but the intake, 'n exhaust manifolds from a 1962 to 'bout 1964 Chevy II, with the 2.5l, I4, will bolt right onto yer motor,...
No water, No extra pump needed,....

 

[GA_Boater]

I am restoring 1935 Dodge runabout and will be replacing the original engine with a Mercruiser 140 - serial number 0A432326/ 1985 - setup as an inboard. I would like to use the original mechanical tachometer. Is it possible to convert the Mercruiser electrical connections to run a mechanical tach? Distributor conversion kit?

Thanks

I doubt you will find mechanical tach drive distributor for a Merc 140 because they all have electrical driven tachs. No, you can't convert the electrical pulses to a mechanical drive with a kit because it isn't made. You would have to design such a thing and make it.

Does anyone have experience with the Cable X made by Abbott Industries used to convert a mechanical speedometer to an electric speedometer? I will check with Abbott next week - hoping it can be modified to convert my tach??

The Cable X goes the other way. It converts the electronic pulses out of some transmissions to a cable drive for a mechanical speedo. Kind of what you are looking for, but I'm not real sure how pulses per mile can be converted to RPM or if the input signals are compatible.

 

[gm280]

Of course anything IS possible, but unless you know about microcontrollers or PIC controllers and stepper motors and can figure out the ratios to do the conversions, you are better off using a modern pulse tach... You would have to take the pulses from your engine and digitize them send them to a microcontroller or PIC controller and then write a little program to convert the pulse counts to drive a stepper motor that would dive the cable to your present tach. So yes it can be done, but not without a lot of effort and understand of how all those things work...

 

[Silvertip]

GM has built a lot of four cylinder industrial engines over the years and I would expect at least one of them had a distributor with a mechanical tach drive. Even early Corvettes had mechanical tach drives and yes, they were V8's. It may be worth a stop at a GM parts department. Just talk with someone that is older than 18 because they haven't mastered the art of "look-up".

 

[Scott Danforth]

contact D&D speedometers in the twin cities, or the speedometer shop in Milwaukee and have your mechanical tach converted to a pulse tach if you want to preserve the face of the existing tach and not buy new gauges.

there is no mechanical tach distributors available for the GM inline 4. period. old flat-head 4's yes, the GM 3.0 - not a chance.

the other choice is find a V8 mechanical tach distributor and remachine the housing for the 4-cylinder cap. you will spend more money than having your tach converted, however you can then use the mechanical tach.