1978 Evinrude 70HP- Trouble starting/idling/bogging under load

[evinrude2323]

Hi All,

I recently purchased a 1982 starcraft that has a 1978 EEvinrude 70HP 3cy 2stroke engine. Its electric start with a steering console. Previous owner stated it bogged under acceleration and would die. I took it out for a leak test and can confirm this was the case. I got it opened up and thoroughly cleaned all three carbs. Boat doesn't want to start and when it does, it runs a few seconds and dies. I just hooked it up to a fresh tank of gas at 50:1 ratio. Where should I begin? I have rebuilt engines in the past (motorcycle) and have done alot of mechanical car projects, but this is my first outboard and my first 2 stroke. When it is struggling to start, sometimes it will seep dark oil out of the bottom unit right before the prop. Any ideas on where to look? I checked compression and all three are at about 115psi. Checked spark and we have spark on all 3. The only thing I noticed was the plugs were wet with oil when i pulled them. Turned it over a couple times to blow out any excess in the cylinder but still same issues. I'm using muffs in my driveway if that changes anything. Got a manual coming in about a week but if anyone knows where I should start, let me know.

 

[racerone]

Compression should be around 140 PSI.-----Load test the battery.

 

[saltchuckmatt]

Did you try a spark plug jump test or just see that it has spark?

 

[Nordin]

Check fuel pump diaphragm.
If bad, fuel will enter the crank case direct from the fuel pump not going through the carbs.

 

[Crosbyman]

When it is struggling to start, sometimes it will seep dark oil out of the bottom unit right before the prop

most likely carbon and sludge wash out from extra fuel on those et oil plugs

 

[evinrude2323]

Compression should be around 140 PSI.-----Load test the battery.

13-14v like a car battery? And maybe rings are worn?

 

[evinrude2323]

Did you try a spark plug jump test or just see that it has spark?

Haven’t tested for spark but I will this evening when I have another set of eyes to turn the engine over for me

 

[evinrude2323]

When it is struggling to start, sometimes it will seep dark oil out of the bottom unit right before the prop

most likely carbon and sludge wash out from extra fuel on those et oil plugs

So just unburned carbon sludge? Or where is this material coming from?

 

[evinrude2323]

Check fuel pump diaphragm.
If bad, fuel will enter the crank case direct from the fuel pump not going through the carbs.

I have a feeling this is it. Would this explain the seepage on the lower end?

 

[Crosbyman]

So just unburned carbon sludge? Or where is this material coming from?

the exhaust housing is full of carbon deposits & unburnt fuel-oil when inefficient 2 stroke engines blows out the cyl fumes when the incoming load of new fuel-oil fills in the cyl. space on the downstrokes.

Probably 30% of good fuel and oil is waisted by the 2 stroke design which is why DI engines are so efficient. My 75HP ETEC burns less gas (.6L/h trolling) than my old carbed Merc 50

 

[evinrude2323]

the exhaust housing is full of carbon deposits & unburnt fuel-oil when inefficient 2 stroke engines blows out the cyl fumes when the incoming load of new fuel-oil fills in the cyl. space on the downstrokes.

Probably 30% of good fuel and oil is waisted by the 2 stroke design which is why DI engines are so efficient. My 75HP ETEC burns less gas (.6L/h trolling) than my old carbed Merc 50

Should I be cleaning the exhaust housing? Or what is causing it to run so poorly in your opinion? I’ll buy a new engine down the road but I wanna use this one if possible

 

[racerone]

Checked thermostat ?----Does spark jump a gap of at least 3/8" on the 3 leads ?---The motor is 45 years old and possibly 5 owners.-----Remove head gasket to inspect cylinders.----Head gasket is cheap compared to ignition parts / carburetor kits or an hr labor at a big shop !

 

[saltchuckmatt]

"wet plugs" "starts and dies" "black fluid running from lower"

Spark jump test....buy a cheap one, $15 at any auto parts store or get a nice one online.

Could be one of many electrical issues. Rule out each thing and move on.

Once running, take it out on the water and magically watch the sludge go away.

 

[evinrude2323]

Checked thermostat ?----Does spark jump a gap of at least 3/8" on the 3 leads ?---The motor is 45 years old and possibly 5 owners.-----Remove head gasket to inspect cylinders.----Head gasket is cheap compared to ignition parts / carburetor kits or an hr labor at a big shop !

3/8” spark? Like from plug to engine block? And if I pull the heads do I have to mess with timing? I’m down to rebuild if necessary

 

[racerone]

Just 22 bolts to remove cylinder head.----No timing issues involved.-----Easy on a fresh water motor.----A simple test device is used to check peak output of the electronic magneto.----Buy one for say $10 or make one with wire , cardboard and glue.

 

[evinrude2323]

Just 22 bolts to remove cylinder head.----No timing issues involved.-----Easy on a fresh water motor.----A simple test device is used to check peak output of the electronic magneto.----Buy one for say $10 or make one with wire , cardboard and glue.

Picked up an inline spark tester and will test soon. What’s the name of this other device and I’ll order it along with new head gasket

 

[racerone]

Some " blinking light " spark tester will fool you.

 

[evinrude2323]

Some " blinking light " spark tester will fool you.

What should I be looking for? Or what tool is actually going to be useful for this? I can test for spark but i guess I’m wondering how I test the gap it sparks. Do I just hold it 1/2” inch for metal and see if it jumps?

 

[saltchuckmatt]

Try this. Nice blue 3/8 crack.

 

[evinrude2323]

Try this. Nice blue 3/8 crack.

I’ll order this.