1978 Mercury 70hp Worth Messing With?

[Berdink]

Assuming it has good compression. Assuming it runs and has a good lower unit.
Is it worth keeping?
It looks like parts are a little hard to come by than my Johnson.

 

[Berdink]

 

[Mc Tool]

Well , if it has all the things you assume it has , wtf not , I mean it looks to be in reasonable nick . If it goes ok and doesnt have any death rattles .
1978 doesnt necessarily mean its got a lot of wear on it ...might be a tidy old donkey . After that I guess it comes down to what you have to pay to get it .

 

[Chris1956]

Check the engine wiring harness, especially the quick disconnect plug. Look for insulation that is falling off.

I would expect ign and carb parts to be avail, as well as normal maintenance stuff.

 

[racerone]

Not a robust lower unit for a 70 HP.----And 2 carburetors for 3 cylinders.----Not on my list of favorite motors.

 

[Texasmark]

View attachment 419536View attachment 419537View attachment 419538

Follow the fuel input hose to the fuel pump attachment point.....look at the hose below it.....I see what looks like that connection is bad.....replacing the hoses is a good place to start. Wiring seems to be in good shape.

Usually new kits in the carbs with a thorough internal cleaning with good compressed air blow out when finished cleaning......water pump maintenance, may just need an impeller (would replace anyway) if the pump housing isn't all scarred up internally from impeller wearing on the surface where you would need a new pump.

If you get to the point of starting the engine (with a fresh, fully charged battery with good clean (internal) connections on both ends of the power cables) and something doesn't respond/perform to expectations, I'd get a wrench on every electrical connection that isn't covered with a rubber cap and back the locking device out a little, move the wire/lug back and forth a few times and secure the attachment. Sometimes corrosion gets in there and messes up the conductivity of the connection.

 

[Berdink]

Yes, all the fuel lines need replacing. I won't even attempt to turn it over without replacing all of them - they are dried stiff.
And yes, definitely will replace the impeller.
.
It was given to me by an older lady I work with who recently lost her husband. She knows I like boats and fishing and told me to just come and get it.
.
From my research, it's far from having the support of a Johnson/Evinrude.
So I was wondering if it was even worth attempting to get it usable.
.
She said her husband had it running last year.
.
I'll first remove all the fuel lines, then do a compression test and check the spark with a 3/8" gap spark tester today.

 

[Chris1956]

Gee, how do you define "Support for Johnson/evinrude"? They have been out of business for a long time. Dealerships are closed. Parts are avail via mail order.

Mercury is still in business. Dealers will tease you for having an old motor, but will mostly help.

 

[Berdink]

When I go to Crowley Marine or Boats dot net, I see a lot more parts availability for Johnson/Evinrude 70's 70hp, than for this Mercury.

 

[Berdink]

139, 137, 135.
Spark jumps a 1/2 inch gap on 1 & 3.
No spark on #2. No spark even at coil of #2.
.
Really funky build for getting to the carburetors, but I guess it's worth getting it to run.
.
I'll be putting it away for now and perhaps make it a winter project.

 

[Berdink]

Some stinky old fuel in the carbs. And the hoses look original.
I'll need to clean up some corroded wiring and clean the carbs, and run all new fuel lines.
But like I said, I'll make it a winter project. But at least I know it's worth getting it running.

 

[Chris1956]

I assume you tested for power at the #2 coil primary? A standard voltmeter may not show the quick pulse that fires the coil.

You might swap coils and see if spark returns to #2. If so, replace the coil. If not the stator or CDI unit is likely bad. There should be ohm specs for the stator.

 

[Berdink]

I assume you tested for power at the #2 coil primary? A standard voltmeter may not show the quick pulse that fires the coil.

You might swap coils and see if spark returns to #2. If so, replace the coil. If not the stator or CDI unit is likely bad. There should be ohm specs for the stator.

Thanks, I'll look further into it this winter. I need to get back to more pressing projects. I mainly wanted to verify the motor had good compression to know if I should just part it out or not. But I'll give it a chance to live again.

 

[Mc Tool]

I assume you tested for power at the #2 coil primary? A standard voltmeter may not show the quick pulse that fires the coil.

I just bought this stuff

To make a dva , only need one of each but minimum buy is 10 or 20 , whole lot cost about 12 bucks , as opposed to 80- 100 to buy one .