1976 Evinrude 70 HP need help

[Turn4fun]

I'M AT MY WIT'S END!

So I replaced the upper and lower seals, including new O rings, new spaghetti seal in the crankcase halves, sealed with Loctite 515. The fuel pump was pumping strong, but for good measure I installed a new diaphragm kit anyway. Reset timing and link & sync. Started right up, idled well on muffs and sounded right as I advanced the throttle (not too much mind you). Drove 20 minutes to the lake to test run and once it was in the water it didn't want to start. Once I finally got it started, I set the idle speed with it in forward and it idled around well. However, if I gave it ANY degree of throttle at all it would fall flat. Back home in the driveway on muffs it once again started right up and stayed running, idling smoothly but intermittently cutting out on a cylinder.

 

[racerone]

Hard to believe is not , after all this work.

 

[flyingscott]

Did you ever make a video of the linkages you would not be the first one to have the timing linkage stick after sitting.

 

[oldboat1]

^^good idea to confirm.

Sad to hear you didn't get a fix yet. Think I would do some back checking (probably doing that). Do the leak test again with some spray carb cleaner; Recheck spark and compression.

You had a temporary fix when removing and replacing flywheel -- could mean the whacking and banging temporarily repaired a short. Might think in terms of grounds (thinking of a mag plate ground, maybe running a ground from the block to the mag/throttle plate and see if that makes a difference. I think there are a couple of other grounds as well, maybe at the power pack location.) Same with abrasions or other wiring issues, although think you were through that.

An out-of-box suggestion might be an exhaust blockage. On another make and model, I had continued issues until I discovered and removed an ancient mouse nest way up in the exhaust housing, under the powerhead (a hazard in the motors I like to restore). But an exhaust blockage somewhere could give you the performance issues you describe, maybe exhaust ports in the leg if that applies, maybe at the exhaust adapter or gasket, maybe in the l.u. affecting the thru hub exhaust -- additional back pressure overwhelms. (Runs OK on muffs, but stalls out in the water. BTW, would run in a barrel rather than muffs to insure some back pressure for testing -- sink it deep and keep the hose running, low throttle. Monitor temps.)

 

[Turn4fun]

Exhaust blockage might be feasible except that it ran fine at WOT on the lake two weeks ago. I double checked for leaks with the spray test, nothing happened. I did use a new gasket between the powerhead and exhaust adapter. Here's a video of how I set the link & sync.

 

[Turn4fun]

Here is a video of it idling at 1000 RPM. You can hear it surge randomly. Also doesn't quite sound right as I advance the throttle slightly.

 

[racerone]

Why is the bottom coil wire going to the # 2 cylinder ?

 

[flyingscott]

My impressions are you are not running on 3 cylinders and I can hear a crack that sounds like a spark plug arcing. Your spark plug wires might be to long also.

 

[flyingscott]

Why is the bottom coil wire going to the # 2 cylinder ?

It's not his spark plug wires are that long that they loop around each other

 

[racerone]

Looked on a bigger screen , the plug wires are correct.

 

[Turn4fun]

Should I cut them down? I thought it was odd that they were so long, the top one came with it's lead already short.

 

[flyingscott]

I would make them shorter and how sure are you that motor is running on 3 cylinders.

 

[Turn4fun]

It really doesn't seem to be running on all three all the time. As I was shooting that vid, that is the first time that I heard the snapping. Snapping goes away when the engine surges (all cylinders hitting at that point). Seems to me that the plug is firing but combustion is only occurring intermittently. I cut the wires down so they are all the same length and not crossing each other, no change.

 

[flyingscott]

Fire it up in the dark you might be able to see if anything is arcing.

 

[Turn4fun]

OK new developments....

It started easily and ran on all three in the driveway yesterday so I ran to the lake real quick for a test run. Once there, again the hard starting occurred and randomly dropping the third cylinder. I was able to keep it running however and eventually it stayed running on all three. When it did, in gear idle was great, acceleration was normal and WOT was normal. GPS verified that I was getting my normal top speed as well. However, at neutral idle it wanted to cut out again. After running around for a while, I shut it down for 5 minutes and tried to restart. This time it was really hard to start and did not want to stay running.

I began to theorize that perhaps the one carb was not delivering an ignitable mixture at idle since I know all three plugs are firing. I pulled the air box cover and put a small shot of ether into each of the carb throats one at a time figuring that the dead would perk up. What happened is #1 and #2 each just bogged down for a couple of seconds and then picked up a little faster than normal for a couple of seconds. #3 however did nothing.

Today I decided to swap the top and bottom carbs to see if the problem followed. I started it up first to make sure #3 was still at fault but to my surprise only #1 was running and #2 kicking in randomly. I then made an interesting observation about #2 and #3 that can be seen in this video. What could be causing this?

 

[oldboat1]

Did this leaking start after you shortened plug wires? If so, I would suspect the boot might not be fully seated -- make sure the spring connector is positioned correctly and the plug snaps securely into place. Boot needs to fit tightly on the plug. You had replaced those bottom coils -- boots new as well?

The plug insulator could be cracked. Might check it and clean the plug with some WD-40, then dry it off. Spray a little WD-40 in the boot as well, and insure the little nut on top of the plug is screwed on tight. I would be inclined to try a different plug even if no damage is visible. Be sure the plug base is clean and tight.

Given your ongoing issues, I would also check and probably reattach ground straps -- one on top of the #1 coil, one at the rectifier base, one at the base of the power pack (I think).

 

[Turn4fun]

Plugs are 3 days old and gapped at .040. Boots and wires are new, came with the coils. The boots fit tight and are fully seated. I'll recheck the grounds but they all looked good when I checked before.

I did notice that the boots on these two coils are not as thick as the top coil (which is two years old). The top one did not have any arcing. I think I'll see if I can find some heavier boots.

 

[oldboat1]

Think that's you: 1989-1975 49 CID 3-Cylinder QL77JC4 L77JC4 0.03

Plug preference is like oil preferences (many opinions). Could also try a surface gap plug -- think the rap on surface gaps is cooler running, good h.s. performance, maybe rougher idling.

 

[flyingscott]

Try putting die-electric grease in the boot then zip tie the boot on to the plug. This may help otherwise replace just the spark plug boot and new plugs. The motor was arcing before you made the wires shorter.

 

[Turn4fun]

Think that's you: 1989-1975 49 CID 3-Cylinder QL77JC4 L77JC4 0.03

OMG could it really have been this simple. I thought this was a typo at first as my manual states (more than once) that the spark gap is 0.04. I started Googling and every chart I found online agrees with you, 0.03. I was all set to track down new boots but decided to re-gap first. Much to my delight, it started right away and ran without any misfires and no arcing through the boots. Ran it for several minutes and then did two restarts after 10 minute rests and no issues appeared. Too windy for a test run at the lake today but I'm planning to tomorrow. I feel more confident about it this time but keep your fingers crossed anyway.