1972 Mercury Outboard Gauge Questions

linckeil

Petty Officer 3rd Class
Joined
May 11, 2007
Messages
76
I have been looking for a set of period correct gauges for use on my 1973 16 foot Donzi powered by a 1972 Mercury 1400.

I came across a full set of gauges that is the exact style I have been looking for. The guages I picked up are out of a mercruiser I/O powered boat, so some of them are not applicable to a 2 stroke outboard. So here is a list of the gauges I have and I'd like your input on whether or not they can or should be used for my outboard:

1) 60mph speedometer - I see no issues with using this.
2) 5k tach - I will not be using this tach as a 2 stroke outboard should have at least a 6k tach, which I already have.
3) engine temp - could this be used on my outboard? if so, what sending unit would I need and where would I mount it?
4) amperes - could i use this gauge? The charging system on my outboard is much more simple than that of an I/O which would have an alternator.
5) battery - i assume this is a volt gauge. I see no issue with using this for my application.
6) trim guage - my motor does have power trim/tilt. although you can clearly see whether or not an outboard is trimmed, versus an I/O. regardless, could the power trim gauge be used? what kind of sensors/sending unit would be required on the motor?
7) oil pressure - i would not be used on a 2 stroke motor.
8) fuel gauge - i see no issue in using this, so long as i get the proper sending unit. anyone know specifically what sending unit I'd need?
9) vacuum - does a 2 stroke create vacuum? where would the vacuum source be on the motor? would it make sense to use this?
10) hour meter - I see no issue with using this for my application.

I'd like to also get a water pressure gauge - those are specific to outboards and i am keeping an eye out for one.

Here's a picture of the style gauges i have - note these are not my actual gauges, but this is what they look like.

http://www.classicboatwork.com/classicparts/gauges/othergauges/4783.jpg

so what are your thoughts on using these gauges on a 2 stroke outboard? Thanks.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,030
Re: 1972 Mercury Outboard Gauge Questions

A tach from an I/O from that era will very likely not work on an OB.
Engine temp will not work and that OB has no thermostat. Engine will run dead cold, most of the time.
Ampere gauge will not work, unless you run a new wire from rectifier to dashboard and another new wire to battery.
Volt gauge will work, connect to white wire.
Trim gauge will not work as motor has no sender.
Oil pressure will not work as 2 cycle motor has no oil pressure.
Vacuum gauge may work, but why do you care? it will not show you anything useful, IMHO.
Hour Gauge will work. Connect to white wire. What are you expecting to use hour reading for?
I doubt you will find a matching water pressure gauge, however, it is a real good gauge to have.
 

linckeil

Petty Officer 3rd Class
Joined
May 11, 2007
Messages
76
Re: 1972 Mercury Outboard Gauge Questions

thanks for the reply. the primary gauges I want to have is speedo, tach, fuel, volt, and water pressure (if i can find it). As for the other guages I mentioned, they all came with the entire set, so why not look into what my options may be?

the 5k I/O tach i do not plan to use anyway as I have an OB specific 6k tach.

ampere gauge will require additional wiring as you mention - wiring will not be in stock control harness and would require it's own specific wiring (not jumped from any other sources). I was wondering if it would work with the simple charging system found on these motors versus the more complex system found on an I/O? i'm guessing it would?

as for the vacuum gauge, i find them extremely useful on 4 stroke motors for purposes of tuning, monitoring fuel consumption, timing adjustments, and overall engine diagnostics - but have never run a 2 stroke with one. do you see no benefit to vacuum gauges in general, or just on a 2 stroke motor?

hour gauge would be used to determine how many hours the motor has been run - just as it is on any piece of equipment or engine equipped with one. again, if i have it and it'll work, why not use it? good for determining servicing intervals as well.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,030
Re: 1972 Mercury Outboard Gauge Questions

Amp gauge will work. Motor can charge up to 9A at near WOT, much less at lower speed. Gauge may not register very much. Gauges must be connected in series with charging system, in your case, between red wire on rectifier and battery + post.

Vacuum gauges are not used for tuning outboards. There is no intake manifold to connect gauge to, on that motor. carb vacuum is not useful, at least I cannot think of a use for it.

Hour gauge will measure running hours. Not sure what maintenance intervals you can calculate. No oil to change, no valves to adjust, no timing belt to replace. Change the gear oil once or twice a year, pump some grease into the zercs and use fresh gas. Those are the only maintenance items.
 
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