Ok, 1975 evinrude 75 horse power 3 cylinder. VEEERRRYYY interesting problem here and I need some help.
The engine starts and runs fine. In low RPMs it has no problem. you move the control box down to WOT, and it develops a shake. Will not gain power like its missing or something. Back off a little it is fine and you can SLLLOOOWWWLLLYY idle it up to WOT. The other interesting aspect is that when you are wide open, every 2 minutes or so, the engine will miss hard. Like, drop you off plane like you shifted to neutral hard, for about 5 seconds. Then it is back, like put you in your seat back. here's what i have done:
Cleaned/rebuilt carburetors
Rebuilt fuel pump
New gas tanks/fuel lines/hoses
New coils (the good CDI kind)
new spark plugs (the good kind)
New rectifier
Seafoamed engine (shock treatment version)
changed prop pitch from 17 to 15 aluminum
linked and synced
Fixed flywheel (key pin sheared)
Retimed engine according to factory specs
checked compression (125 all cylinders)
So I think the problem has to do with the ignition system. It's like the spark is there, but not at the right time. So I'm thinking power pack or maybe base timer? I tested the power pack and I am getting wierd readings according to CDI's troubleshooting pdf, but the base timer seems to test right where it should between 1-2 megaohms. the power pack, according to CDI, should read between 100-200 ohms accross the sensor to coil nodes but I am getting readings in the megaohms!! However across the second coil to sensor it is 1 megaohm higher than the other two.
I realize that everybody says the DVA readings are better, but I don't have access to one, and I am newly married and don't have the money. Furthermore the boat shops here will read ohms, they don't have dva meters
I checked because I thought they could run the test and I pay them a diagnostic fee and it would be cheaper.
I have been through a lot, so if I am missing info you need let me know. I am truly stumped here. Actually contemplating completely redoing everything, power pack, base timer, stator, everything!! Just because i want it gone.
please help me:facepalm:
The engine starts and runs fine. In low RPMs it has no problem. you move the control box down to WOT, and it develops a shake. Will not gain power like its missing or something. Back off a little it is fine and you can SLLLOOOWWWLLLYY idle it up to WOT. The other interesting aspect is that when you are wide open, every 2 minutes or so, the engine will miss hard. Like, drop you off plane like you shifted to neutral hard, for about 5 seconds. Then it is back, like put you in your seat back. here's what i have done:
Cleaned/rebuilt carburetors
Rebuilt fuel pump
New gas tanks/fuel lines/hoses
New coils (the good CDI kind)
new spark plugs (the good kind)
New rectifier
Seafoamed engine (shock treatment version)
changed prop pitch from 17 to 15 aluminum
linked and synced
Fixed flywheel (key pin sheared)
Retimed engine according to factory specs
checked compression (125 all cylinders)
So I think the problem has to do with the ignition system. It's like the spark is there, but not at the right time. So I'm thinking power pack or maybe base timer? I tested the power pack and I am getting wierd readings according to CDI's troubleshooting pdf, but the base timer seems to test right where it should between 1-2 megaohms. the power pack, according to CDI, should read between 100-200 ohms accross the sensor to coil nodes but I am getting readings in the megaohms!! However across the second coil to sensor it is 1 megaohm higher than the other two.
I realize that everybody says the DVA readings are better, but I don't have access to one, and I am newly married and don't have the money. Furthermore the boat shops here will read ohms, they don't have dva meters
I checked because I thought they could run the test and I pay them a diagnostic fee and it would be cheaper.I have been through a lot, so if I am missing info you need let me know. I am truly stumped here. Actually contemplating completely redoing everything, power pack, base timer, stator, everything!! Just because i want it gone.
please help me:facepalm: