115 evinrude not running on all cylinders under load

[Dallas214Stars]

So I’ve been working on boats restoring and cleaning them up as well as getting engines fixed up and ready to sell for a few months now. Have experienced the usual problems and studied how to fix them. But the last 3 boats I’ve bought have all done the same thing and I really need to figure out what’s causing it because now it seems to be like a common issue. I’ve done research and have seen it said to be many different things but I wanted to get y’all’s experienced opinion on what the most common culprit is so I can start there. I’ve read cables, power pack, plugs, plug wires, etc. the list goes on and on. When I idle I have full power engine revs great but under load or in gear it has trouble starting up and will die if I idle and at WOT I am going 8mph with the butterfly’s completely flat open. Here is a video of the motor if you can hear it’s at WOT we’re going 8mph don’t touch the throttle at all it slows lags up then dies out at WOT on its own. Any help appreciate thanks folks!

https://youtu.be/d9j9snLiLuY

 

[racerone]

Fact ---When you rev up an engine in neutral they all SOUND GREAT and it means nothing !!--They will rev up running on 2 of 4 cylinders !!-------Model # of your motor.----First thing to do is a compression test.----Simple and no money spent.---Post the numbers.----Very clear to me that it is only running on 2 or 3 cylinders.------Check sparkplug wires / orange wires from powerpack to coils too.----Motor is a 1973 to 77 model.----Some simple trouble shooting will find what is wrong in no time.

 

[Dallas214Stars]

Fact ---When you rev up an engine in neutral they all SOUND GREAT and it means nothing !!--They will rev up running on 2 of 4 cylinders !!-------Model # of your motor.----First thing to do is a compression test.----Simple and no money spent.---Post the numbers.----Very clear to me that it is only running on 2 or 3 cylinders.------Check sparkplug wires / orange wires from powerpack to coils too.----Motor is a 1973 to 77 model.----Some simple trouble shooting will find what is wrong in no time.

Ya I figured something like that with the revving in neutral thanks for the info. Already checked compression in it 120 in all 4 cylinders. Put 4 new plugs in yesterday experienced the same issue. Plug wires look good but I’m sure need replacing. Haven’t checked the orange wires but I also have read that the power pack or coils could be bad. Definitely have done some troubleshooting but wasn’t able to figure out the exact problem.

 

[racerone]

Answer this question.----Do you have spark that jumps a gap of 7/16" on each lead, yes , no or not sure why that is important.-----I believe all the terminals on the powerpack are marked as to where they go.---Perhaps check that.----Note ---I have more than one of these motors for parts / rebuild.