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VIDEOS - 88 Merc 115.. Can someone figure this out??

8

89PartyHut

Contributing Member
Motor at idle:
https://www.youtube.com/watch?v=OQAFmqVRIV0&list=UUr_hYZkhnFUMLVmeMULQo6A

Motor at WOT:
https://www.youtube.com/watch?v=TK-HuZzExmU&list=UUr_hYZkhnFUMLVmeMULQo6A

At WOT you can see and hear my issue. It is sputtering and kicking. When I was refreshing the motor I have replaced the stator, rectifier/regulator, rebuild all 3 carbs with genuine parts, new 5/16 ID fuel lines, I removed the fuel filter (for testing purposes), My fuel pump is at 4-5 PSI at idle, I am using a external 6 gallon fuel tank for testing. I have 125psi compression across all 6. Oil injection has been removed/blocked and I run 50:1 premix.

Please help..
 
Which motor are you talking about! On the 4 cylinder Merc, you have an ignition issue--it's dropping a cylinder (or more) under load. I suspect a bad coil. You can confirm this with a WOT plug test--the darkened/ wet plug will be the 'bad' cylinder. Do NOT let the motor idle after running the hell out of it. Cut it off fast as you safely can and yank plugs.

Jeff
 
I did the WOT and kill engine test. Used a towable raft to hangout behind the motor while I pulled the plugs. All 6 plugs look identical. None look wet.
 
Ohmed out the trigger.. all wires tested the way I read to test from 1100 to 1400 ohms. From what I understand this is in spec.
 
it looks like one of the switchboxes were replaced at some point.. One is black the other is kinda see-thru yellow/orange color.
 
Went out fishing around the banks with it. Its so strange.. Sometimes it runs great.. other times something is clearly wrong.
 
Get a spray bottle and fill it with fuel/oil mix, have someone drive the boat and you spray the fuel mix into each carb. This will give you a definite answer to ignition or fuel loss.
 
I replaced upper switch box and my WOT issue has resolved. However I still have a problem with idle miss fire. I assume it is the trigger or the lower switchbox. I also have been told that the Bias circuit could cause this. I am going to ohm them out next.
 
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