1970 Evinrude 18hp Trottle issue

[davidmbv]

Maybe recheck compression with different tool to make certain the compression is low. I would go ahead and replace the head-gasket now that it’s off. If that doesn’t fix it….
Maybe get it running and use timing light to see if your dropping a cylinder, intermittent spark/only running on one cylinder. If so, then track down why you are losing spark.
Clean carb ?

 

[jimmbo]

To me that Head Gasket looks like it has been reused a few Times. Head needs a good cleaning and checked for Warpage and a Lapping
What do the Crowns of the Pistons look like? Covered in wet blackish Goo?

 

[racerone]

The head is warped.----Resurface it on a piece of glass and emery paper.----Install new head gasket.----Test run.

 

[frustratedboater]

Maybe recheck compression with different tool to make certain the compression is low. I would go ahead and replace the head-gasket now that it’s off. If that doesn’t fix it….
Maybe get it running and use timing light to see if your dropping a cylinder, intermittent spark/only running on one cylinder. If so, then track down why you are losing spark.
Clean carb ?

I appreciate the detail.. yes, went through the carb 3 times and the low & high speed fuel circuits are clear.
I'll check the timing and see whats going on. Strange thing is right at 3/4 throttle it dies off fast but gradually like its running out of fuel. The pump is new and there is fuel. Even re-checked the points and they are snug .20 ths' with the feeler.

 

[frustratedboater]

To me that Head Gasket looks like it has been reused a few Times. Head needs a good cleaning and checked for Warpage and a Lapping
What do the Crowns of the Pistons look like? Covered in wet blackish Goo?

Agree and will do that. Everything looks black and slightly oily. Cause of the black?

 

[racerone]

Thermostat stuck open ?

 

[frustratedboater]

Thermostat stuck open ?

Therm is fairly new and operated during test.

 

[racerone]

Ignore the black stuff !

 

[frustratedboater]

Ignore the black stuff !

Gotcha
Think I'l check ignition but really think the rings just need replacement and a good cross-hatch cyl. hone

 

[cyclops222]

1970 engine might need it. Also allow a check of rings operating correctly.

 

[racerone]

Resurface the warped head.----Install head with a new gasket.-----Post compression numbers.-----Test run.

 

[frustratedboater]

Just to circle back on this motor and completed the following:
-I had split the case, replaced the rings, honed cly's, and new head gasket.
-Checked the carb for the 6th time over and high speed jet is clear.
-Ohms tested the coils and .007-.006 (going off memory-out of town).
-Points contacts are clean
-I saw a short in one of the spark leads in the evening and was one was arcing to coil plate and replaced both with new copper core leads. and fixed that. Though it was it
-Spark is jumping 1/4"

I dunked it in the ramp. Strapped the boat down and ran the throttle up to full and still dies off back to idle. I even pumped the bulb during and is not the fuel pump. Would failing condensors be causing this?
Only parts still origional is carb, coils, points/condensors. Don't enjoy throwing parts at it. Recommendations?

 

[saltchuckmatt]

Just read the thread, I don't see the new compression numbers nor do I see that you sanded the head. Was that done?

 

[frustratedboater]

Just read the thread, I don't see the new compression numbers nor do I see that you sanded the head. Was that done?

I did purchase a new compression tester and still got 70 on each cyl. and should be 110 ish' I tested it to my compressor just to test and seemed correct. the reeds were all seated. I believe I did run the head over 220 and saw no depressions. I'm out of town now. I'll straight-edge both surfaces when I get back in town.

 

[saltchuckmatt]

"I believe I did run the head over 220 and saw no depressions."

This one is hard to believe. They are all out of spec.

 

[frustratedboater]

Coil testing question on this motor. I have a multi meter and performed the following tests on the coils: and the lowest setting starts at 400 ohms. Disconnected and isolated each coil and was getting 000.6 from both primary wires. When I touched the spark lead and the black ground nothing. Also the other little red wire (connects to points) to spark lead, also no reading. Should I expect diffrent readings?

 

[Nordin]

Secondary side of the coil (HT wire to one of the thin wires) should read about 5-8kOhm.
You need to change the setting of you multi meter.
If you have it at 400 Ohm range it will read infinity when measure secondary winding of the coil.

 

[frustratedboater]

Secondary side of the coil (HT wire to one of the thin wires) should read about 5-8kOhm.
You need to change the setting of you multi meter.
If you have it at 400 Ohm range it will read infinity when measure secondary winding of the coil.

I wish I could. My meter (the one I purchased) 400 is the lowest. I'll see if a friend has one that low. Thanks!

 

[Crosbyman]

??? what scales do you have I never saw a VOM that can't measure a few thousand ohms. ...any cheap analog 20$ meter will work for you.

Testing an Outboard Coil with a Multimeter using an ignition coil from the Johnson H or T

Multimeter testing of Johnson outboard coils

pochefamily.org

 

[film495]

I'd put points and condensers in it just to rule that out.

When you checked the head, did you use a straight edge? I did one a while ago and by eye it looked fine, but it was very much not flat when checking with a straight edge. Easy job to hone it, took like 30 minutes.