TOPIC: New 1975 Merc 1500 Questions

I realize once I get manuals I will probably be able to get these answered, but what gauges can you hook up to the 1975 Merc inline 6?
Can you get an engine temp? Where does the trim indicator get its data? I assume you can hook up a tach with an engine hours timer, and there is no oil pressure sensor since the oils premixed.

Tach is a given...you can get a seperate hour meter if you want to run a vintage tach or find one that will work with your motor that has one built in. No idea about a temp sensor but i would imagine you can. You can put a water pressure gauge on it too...which i highly recommend.

Interested to hear about any trim position indicators as i want to put one on my 1350 also.

What wire pairs go from the motor to a water pressure gauge? Do you have to install a sensor?

The water pressure gauge is the sensor. Just run a hose off the top of the engine where the tell tail is and T it off there.

Next to a tachometer, a water-pressure gauge is the most important instrument needed for an outboard engine. A water-pressure gauge will alert you to a decrease in water flow due to a worn impeller, internal water-passage blockage, or an overtrimmed engine. By the time a temperature gauge indicates the engine is overheating, engine damage could already have occurred. Since a water-pressure gauge operates on direct water pressure from the engine, not electrical current as a temperature gauge does, it is more reliable and instantaneous in its readings.

THANK YOU! I will need to learn how to hook it up. Do any of the service manuals describe how to hook it up?

Wait a sec... you mean I will need to run a hose line from the engine to the gauge on the dash?

Yes

Yes,

a quick google search turned up this:

http://www.diy-boat.com/content/view/151/49/

The following instructions are for our Mercury 150-hp V-6 outboard and also apply to Mariner V-6 models. A water bypass hose on top of the cylinder block made for an easy one-hour installation. Some installations, however, are much more difficult and require drilling a small hole in the front port corner of the lower engine cowling, or removal of the pipe plug from the cylinder-block cover. Included with the gauge are complete installation details and diagrams for all makes; follow the instructions carefully.

First, remove the cowling, cut the bypass hose with a utility knife about 5cm to 7.6cm (2" to 3") from the 90· fitting on top of the cylinder block. Attach the female pipe-to-tube adapter on the plastic tee, then insert tee ends into the hose and secure with cable ties (Figure 2). On V-6 models, the tubing is fed through the cable harness retainer. Because our engine didn't have a spare slot, we doubled up with another cable and filed the hole to accept the extra width. Now, loosely route the tubing through the harness retainer, under switch boxes on the starboard side and up to the water bypass hose. Engines differ you'll need to find a clear route. Install tubing on the barb of the adapter and secure with tie straps

]So, here is a shot of the instrument panel.


Now, the fuel gauge works, but one of the tank sensors does not. Or perhaps its a loose wire somewhere. Time to break out the multimeter. (Something I AM good at!)

RPM gauge pegs, and is malfunctioning. Again, it could be wiring, or a defective gauge.

Speedometer works, don't know yet how accurate it is.

Trim meter does not work.

I am thinking about removing the trim gauge. I can not see the benefit right now. I just turn around and look to see if its all the way up or all the way down. I spoke with the mechanic at Valentines and he stated that they are constantly getting out of adjustment.

In its place I would use that hole to hold a water pressure gauge. The mechanic stated that the Mercury 1500 inline 6 has 2-4 psi at idle, and I think he said 12-14 PSI at max. So a 20PSI gauge would work perfectly.

While its more expensive, I would prefer to get a matching set of gauges. It just looks odd to have piecemeal. Faria Instruments are the brand of gauges that Nordic Boats uses now.
This is a link to the catalog, which gauge style do you think would look good?

www.faria-instruments.com/docs/fm-0010026a_Faria_Standard_Styles.pdf

I am leaning towards the Dress White, or the Chesapeake White SS, but with so much Brown, Yellow, and white, maybe the Spun Gold, or Euro White Gold.

What about Teleflex? That seems to be the other dominant brand.

Bass Pro Shops sells Teleflex Artic series gauges, and I like those better than the Saraha or Eclipse.

Oh, one more thing... When I get the new gauges in, I'd be happy to share the other gauges if someone wants to salvage them.

When several gauges start to mess up or one for that the first thing I check is the ground! Voltage goes to it but cannot get back to the negative and it has a partial ground. Since most of the gauges rely on resistance it is very important. Gauges for the most part are nothing more than resistors. Hope this helps.

That Airguide tach is probably designed to read off the switch box rather than the rectifier so if someone moved the sender wire (brown) from the starboard side of the switchbox over to one of the yellow wire terminals on the rectifier or if someone replaced the six cylinder switchbox with a 4 cylinder switchbox at some time in the past - that style tach will peg.
T

I would love to get my hands on the tach if you decide to do away with it. I have a future project that it would be perfect for.
Doug

Thom is correct (as usual) that tach is specific for the merc switchbox. If you look at your wiring diagrams when you get the manual you will see the tach wire shown in two locations, one with a dotted line, one solid line. Connect the + terminal on the tach to the switchbox,the - terminal goes to ground.

There is no trim sender on that engine so the trim gauge is Moot.

Doug, I have one that I used on my 75 1150, works well, chrome in good shape. If you are interested I will post it in the classifieds.

Amigoid wrote:

Bass Pro Shops sells Teleflex Artic series gauges, and I like those better than the Saraha or Eclipse.

I bought the same gauges t@ Cabela's...took a few hours to wire but looked good in the end....
I purchased a tach harness on Ebay to hook up the harness..this did not work? so i basically threw away $20.....