Weak spark on 1977 Evinrude 75hp -Problem solved!!

[BonairII]

I checked spark on my new(to me) 1977 75hp when I first got the motor a few days and it was pretty good. I checked it again today and all 3 sparks are weak/thin and not snappy. I drop tested the motor and got some change when I pulled the middle and lower plugs, but not much change in the top cylinder.
When I took the boat out 2 days ago, I did get a very slight 'miss' a couple times, but it when away.

How do I check to see whether it's my coils or powerpack. I don't want to start throwing parts at this motor haphazardly.

 

[F_R]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

First you need to get over that idea of what the spark should look like. That ignition system is worlds away from the "fat, blue spark" that use to be the norm. Will it jump a 7/16" open air gap with ease? If it will do that, there is nothing wrong with it. They actually will jump more than 7/16", but that is a torture for the coils, so not advised. Yes, that 7/16" spark will be thin and clear. It also will knock you right out of your BVD's if you get hooked up with it.

 

[BonairII]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

Well that's good news! I'm still a little suspect of the top coil since the motor didn't seem to stumble much when I pulled it. I just went through some of the grounds and cleaned them up hoping that may help a bit.

Just my luck that I have the weekend to work on the darn motor...and my manual is being delayed by the post office.

 

[BonairII]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

Update: Not great news.

Splashed the boat today. Motor started and we putted out about 500ft from shore. I hit the throttle and she jumped up on plane pretty well. Got to 32 mph(just raised motor 2 holes). We ran for a minute, then I could feel a faint miss then it would go away.

After another minute, the motor bogged right down. I was at WOT and doing 15-20mph, I bumped the key and the motor bogged. I pumped the fuel ball....No change.

I guessing it's a spark rather than fuel issue, but God only knows. :facepalm:

In the video, the motor is surging...but that's because I'm using the throttle on and off trying to get the motor to wake up.

http://www.youtube.com/watch?v=oOY3Ukd0tuQ

 

[mrcrabs]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

CDI power packs have always been a plague for me, similar symptom's and then they just fail completely, I think thats why I got into the tecumseh's...finally a CDI I could fix....LOL

 

[BonairII]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

Is there a reliable way to check coils and/or powerpack to be sure of cause?

 

[BonairII]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

Anyone?

 

[F_R]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

Is it still throwing a 7/16" spark?

It could be other things, y'know. How about arcing out at the plug boot? How about a bad spark plug? And the most serious dread of all dreads, is it ingesting water into a cylinder or cylinders? Those 3 cylinder loopers are bad about that.

 

[BonairII]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

Is it still throwing a 7/16" spark?

It could be other things, y'know. How about arcing out at the plug boot? How about a bad spark plug? And the most serious dread of all dreads, is it ingesting water into a cylinder or cylinders? Those 3 cylinder loopers are bad about that.

Not sure if it was exactly 7/16ths cause the spark tester doesn't have a ruler on it...I just ballparked it. Even when I shortened the gap to see if spark improved spark was what I call 'impressive' on any of the 3 cyls. I didn't 'snap' much either.

Out of curiosity, I went over and checked the quality of spark on my neighbor's '69 Johnson 55hp. His motor runs on a single coil w/ amplifier instead of powerpack, but the coil looks like my coils...but with a screw-in connection. Part numbers are close....0502882 vs. 0502886.
His spark was white and 'snapped'.

Ingesting water? What would cause that? And what are the symptoms of water ingestion?

If you read the initial thread on started on my motor, I had couple hiccups(they were like quick 'misses' or hesitations) when I splashed the boat for the first time a few days ago. They were very quick 'misses' and went away. Other than that the motor ran great for the 30 mins or so we ran it. Ran it at WOT for about 30mins cruising around and had no problems.

Update: Pulled the plugs to see if pistons looked "steam cleaned"(evidence of water ingestion). Top 2 holes have oily film on them. The oil still looks wet. The bottom hole is clean, exactly but I don't know exactly how 'clean' a piston would look if water was getting in there.

I'll pull the head if it's necessary, but don't want to do it just for the heck of it.

 

[mrcrabs]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

Chances are the coils are OK, water ingestion is possable but will show up on the plug and also its a good Idea to check out every thing as F_R said.
BUt I watched your video and I have had that same sympton more than once and I always end up with a dead power pack, When mine go out they will give there first sign by dropping voltage under WOT for moment or 2 like yours then jump back up and go...may even go awhile before they pass away, last year I put my boat in for the fourth of July weekend, a couple runs fishing the day before the party she droped out like yours and then the next morning when I went to go look for the drifting drunks to make my gas money back the power pack was dead, the one before that left me a drifting drunk....LOL
I don't know how to check them other than swap out a known good one and see what happens, coils are easy enough to rule out just find the spec on them and use a Ohm meter,

If you know a friendly boat shop maybe you could borrow a power pack to check it out.

 

[BonairII]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

I didn't see an 'milky goo' or anything suspicious on the plugs. Plug boots look new and the coils look new(the plastic cases anyway).

Can I test the coils on the motor or do I have to remove them? Where do I place the multimeter leads to test them?

 

[mrcrabs]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

double posted...sorry??

 

[mrcrabs]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

do a youtube search on testing coils, or visit www.enginesandmagnets.com Ed Stoller is a good friend of mine and my go to guy for this stuff and since the coils are very similar the should test similar, I think Ed give's some detailed instruction on testing a Capasitive discgarge coil ( pulse transformer )

maybe check the connestion's on the power pack for corrosion or lose wire

 

[F_R]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

I feel like I'm fighting the power pack theory. Hey, I could be wrong. So go ahead and try it if you feel you are correct. I'll make one more comment, then shut up.

EDIT: I had it all written out how to check for water ingestion, but erased it. Too dangerous, you could be burned alive. Instead, I'm going to tell you to take it to a certified Evinrude mechanic. The offender is the exhaust cover on the side of the powerhead. More precisely, the baffle plate between the outer exhaust cover and cylinder block. There are areas around the exhaust ports that are pretty far between bolts. Furthermore, the baffle plate is very thin in those areas. At even the slightest hint of any overheating, those thin areas warp, and the gasket leaks, squirting water into the exhaust ports.

BTW, comparing your Mag CD system to your neighbor's battery CD system is like apples and oranges.

 

[BonairII]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

Mrcrabs, this is what I got from the service manual posted on Marshall public library site:

CHECKING FOR SPARK. Disconnect
spark plug leads at spark plugs and
connect them to a needle point spark
checker, similar to unit in Fig. 0M14-11,
with three gaps used at V2 inch (12.7
mm). Consistent, strong spark indicates
ignition system functioning properly;
suspect spark plugs, timing, improper
wiring to ignition coils or to spark plugs.
Weak, inconsistent spark or spark
from only one or two ignition coils;
suspect sensor coils or ignition coils.
Weak, inconsistent spark from all three
ignition coils; suspect charge coils. No
spark at all; suspect power pack.
WIRING. Engine missing, surging
and failure to start or run can be caused
by loose or corroded electrical connections.
Check all terminals and plug-in
connectors for tight clean contact. Also
check all wiring for short circuit to
ground.



I'm I'm understanding this correctly, if all 3 cyls have weak spark...then I should be suspecting the 'charge coils' in the stator. That sound right?

 

[mrcrabs]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

I feel like I'm fighting the power pack theory

No fight here, I just opined on what I see in his video and my experiance with these CDI electronics on the 3 cylinder J/E, one sure fire way to find out is spend a couple hundered at the J/E dealer for a professional diagnosis as F_R suggest.

 

[BonairII]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

Update:

Just tested all 3 holes for spark. Bottom and middle have great spark(see vid). Top cyl has NO SPARK at all. Weird. I did clean up some of the grounds yesterday, but I don't know remember if I re-tested the spark after cleaning them up. I believe I did though.
http://www.youtube.com/watch?v=XJug-uA-4x0

Going to swap coils now to see if the problem follows the coil. Stay tuned.

 

[mrcrabs]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

and if it doesn't follow the coil what will that tell you? would be a cheap out if its only a coil

also I was looking back at your other vids and I can hear it missing on the hose...It was running to smooth

 

[BonairII]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

Update:

Swapped coils and sanded all connectors and ground points. with the 2 coils. The problem DID follow the coil. No spark at all on the problem coil. So I'm assuming it must be the coil

I'm going to replace all 3 coils...and use the 2 working coils as "backups".

 

[mrcrabs]

Re: Weak spark on 1977 Evinrude 75hp

Re: Weak spark on 1977 Evinrude 75hp

well thats good news, I vote for new coils all around...LOL Good luck and happy boating.