135hp Evinrude '76... lose spark under load?

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mitchum10

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Jul 14, 2010
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I've just replaced about all the electrical stuff on a 1976 Evinrude 135hp.

1 coil
1 power pack
set of plugs
timer plate

Each time I replaced one of these items the motor would run great for about 2 runs... then would need something else...

Now after all the repairs, the engine has spark on all four cylinders, but when I put it in gear and head off out the hole, I can tell I'm down to 3 cylinders.

I was told that when I replaced the first coil, the other 3 were likely to fail at some point in time soon afterward...

I've been told that the reason I'm likely losing a cylinder under load is that one of the 3 old coils is failing, and that it seems fine in neutral, but when under load it fails...

Can this be true...?

(I'm currently waiting for 3 new coils to arrive, but I'm having second thoughts if this isn't likely to be the culprit???)

Thanks in advance to anyone who might be able to help me...
 
HighTrim

HighTrim

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Re: 135hp Evinrude '76... lose spark under load?

I would first ENSURE that you are losing a cylinder while underway. Do you have an inductive timing light? Does it do it when both warm and cold? Does it get to WOT? Why do you feel you are dropping a cylinder? Is it over revving at all on take off?
 
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mitchum10

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Re: 135hp Evinrude '76... lose spark under load?

When first got the boat I thought it ran fine, till my mechanic friend did a compression check and said I was running on 3 cylinders not 4... needed a coil, and boom.... went from top speed (GPS) of 32 to almost 42 - the motor sounded completely different with 4 cylinders than 3 as well.

Ran OK for a day, then wouldn't start. Replaced the timer place and power pack and boom... back to 4 cylinders and ran great for a day. Then at the end of that day, I went out for a last ride with my father, and boom, he and I noticed we were back down to 3 cylinders again (32 mph WOT and sluggish out of the hole as it had been when I first got the boat).

However, the next day, when doing a spark test in the water in neutral it shows spark on all 4 cylinders???

My fried just seems to think it might be a coil failing under load??? I don't get feeling it's a fuel issue as it seems to run pretty smooth even on 3 cylinders and idles pretty well???

Thanks again for your input Chris... any ideas you might have would be greatly appreciated...
 
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mitchum10

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Re: 135hp Evinrude '76... lose spark under load?

P.S. The engine does not sound like it's over-revving when I accelerate out of the hole.

It seems to stay on 3 cylinders hot or cold.

Not sure about the timing light... that would be my friend.
 
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jonesg

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Re: 135hp Evinrude '76... lose spark under load?

Its like replacing one headlight on your car, you know the other one can't be far behind. Do them all.

You can get cheap timing lights at any auto store, mine was $27.

An adjustable spark gap tester will show spark quality , set the gap to 3/8th inch, got mine at autozone for $12. These tools will save you money.
 
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emdsapmgr

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11,551
Re: 135hp Evinrude '76... lose spark under load?

Weak ignition components tend to fail when they heat up to normal operating temps. You may have that issue, since it seems to run better at times. You may be able to rent a timing light at a local auto parts store. It's helpful to diagnose just which plug is failing and a timing light should help you determine that. Check the spark after the engine is heated up to normal temps, then idle it in gear to check the spark.
 
kenmyfam

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mitchum10

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Re: 135hp Evinrude '76... lose spark under load?

Thanks for the help... will look into the timing lights...

Can anyone answer me on what to do about driving it... ??? Shows spark on 4 cylinders, and seems fine at idle, but I know that once it's running it's down to 3....

Is it OK to drive gently, or am I risking losing already replaced parts again?
 
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ezeke

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Re: 135hp Evinrude '76... lose spark under load?

Too risky; it's important to identify which component is breaking down once heated up and replace it before it damages other components. If it's an ignition coil you can warm it with a hair dryer while the engine is running to see if it stays alive.

Bad ignition coils kill powerpacks.

Bad ignition switches kill rectifiers, powerpacks and picnics.

Bad rectifiers burn stators.

The V4 series of motors of which yours is a part had a serious grounding problem with the rack that holds the ignition components. Later models had more grounding straps including ones to each of the cylinder heads. All of the engine grounds need to be very clean and well connected.

You have to be very careful that the powerpack connections are very clean, dry and sealed.
 
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autohead18

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Re: 135hp Evinrude '76... lose spark under load?

it is most likely arcing somwhere @ higher rpm you should check for arcs all wires and coils if this is not the problem it could be in the ignition or possobley the power pack is your key in the control box if so somthing might be getting spark in there when you leave netrual you may also get a shock from the control box if this is happening all you can do is check all conections and clean them and you should find somthing along the way let us know
 
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mitchum10

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Re: 135hp Evinrude '76... lose spark under load?

Thanks, I'll keep it onshore till I get the other 3 coils on it...

Appreciate the help...
 
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mrcj001

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Jul 25, 2008
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Re: 135hp Evinrude '76... lose spark under load?

I have the same engine as you. I had simular issues.

When I used a spark tester, the left bank would spark when I first hit the key. But when I kept cranking, it would loose spark.

On these old engines, you need to inspect ALL the wiring. They get old and brittle.

I found a wire were the insulation was cracked and was grounding out on the rectifier. Once replaced, it solved the spark problem.

Also, the carbs on these engines pretty much have to be perfecty clean and floats adjusted properly. Dont use Seirra brand kits on these carbs. Use the OEM kits from Evinrude.
 
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jalbert34668

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Re: 135hp Evinrude '76... lose spark under load?

I'm having the same exact problem with my evinrude 88' 140hp V4. Runs great fires on all cylinders when in neutral but under load it sounds like its missing on one cylinder, I relaced one bad coil though that would help but same problem I' wondering if your right about having one good new coil is causing the others to be weak or grounding out!! also check your wire from power pack to coils make sure you dont have one on the wrong coil! good luck let me know if anything helps so i can finally get my motor running like it should!
 
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mitchum10

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Re: 135hp Evinrude '76... lose spark under load?

I'm going to spend some time this weekend looking at the wires... the engine is so clean that it's hard to believe that it can be a wire, but I've seen it before on my old Jeep Wagoneer, so I know it can happen...

Once I finally get the 3 new coils and put them on I'll know whether or not it's solved the problem or if I have a grounding problem...

Again, thanks for all the input from everyone... what a great site!
 
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mitchum10

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Re: 135hp Evinrude '76... lose spark under load?

Well, yesterday I decided to fire up the engine since the boat has sat on land for over a week... I put it in the water, cranked it, and boom, back to 4 cylinders on take off!

Drove it out in the bay for about 10 or 15 minutes, came back, turned it off... waited 20 minutes, went back out a little further past the bay this time... and it ran on all 4 all the way for about 20 minutes...

Came back did the same thing again, except this time I waited a couple of hours... and went even further... all 4 continued to work.

At the end of the day I went out one last time... started it... and as I went to plane, immediately realized I was back to 3... I did a long loop and crossed some chop far out in the bay. As I came out of the turn, I could feel the boat accelerating again in a straight line (all by itself), and I was back to 4 cylinders... So I tired to replicate this by going the opposite direction over the chop to see if it would drop back to 3... (thinking maybe a loose ground), but no... it continued to stay on 4... I rode all the way home - all day - on 4 cylinders - a first!

Today, I went out 3 times... it only ran on 3. Tried crossing chop, wake, everything I did the day before.... but nothing would bring it back to 4 cylinders...

If this was a loose ground arcing, wouldn't I feel it slow down and then pick up speed every time the ground made and lost connection? In other words, as I hit chop and so forth throughout my runs, shouldn't I notice this slowing/accelerating felling quite regularly..?

I'm now leaning more toward one of the 3 older coils (still haven't received the new ones yet), as being more of the suspect???

Any thoughts or ideas?

Thanks again...
 
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