1971 Evinrude 50 - sudden power loss

[JT!]

i have already tried replacing my coils to resolve the problem, but the problem CAME BACK. It did seem resolved with the new coils for about 2 hours.

could i have killed the coil? or can a new sparkplug go bad and stop sparking?

cylinder #1 plug is black & sooty
cylinder #2 plug is 5% sooty and very wet.

if i test the plugs, they both spark.

i can idle, and fast troll without problems. anything over a 1/4 throttle, it just doesnt respond. it doesnt bog. like it did before changing the coils.

oddly, the fuel line primer bulb is very soft, but re-inflates quickly, and pumping it doesnt help in the 1/4 to WOT range.

 

[larky]

Re: 1971 Evinrude 50 - sudden power loss

If the top plug is black and sooty then I would say that its running too rich. Now I know you have been through a lot with this motor, so you may have already got the carbs set. But the factory setting are just a starting point (imho) try to adjust a little beyond that setting.

You have probably already read this but here it is,

carb settings by joe reeves:
http://forums.iboats.com/showthread.php?t=167352

 

[JT!]

Re: 1971 Evinrude 50 - sudden power loss

back from my days of racing MX and fixing my own bike, i learned the plug should be a dry caramel/golden color.

so i will check my fuel mixture, once its running.

but for now, how to get above 1/4 throttle. i'm still stuck.

 

[Redneck1]

Re: 1971 Evinrude 50 - sudden power loss

I had a '79 70 hp do about the same thing but mine didn't do it as I was running along but same syptoms idled like a champ but no top end and I found out today it was apower pack. The only differance is mine is a 3 cyl.
Rob

 

[JT!]

Re: 1971 Evinrude 50 - sudden power loss

are powerpacks known to have issues only once warmed up?

my condition happens after 5 minutes of WOT and doesnt heal until next time out on water. even with motor off for 2-3 hours while using trolling motor

 

[JT!]

Re: 1971 Evinrude 50 - sudden power loss

took the boat out again today.

i am now convinced i'm running on one cylinder as my top speed is 7mph, no power, no acceleration.

also answers my question about fuel economy, i've been pouring gas thru an unfired cylinder. double the gas and only 25% OF THE POWER... the working cylinder loses its own momentum from constantly compressing the non-firing cylinder

 

[Okee Jimmy]

Re: 1971 Evinrude 50 - sudden power loss

It sounds like you have a ruptured fuel pump diaphram, allowing fuel to be sucked directly into the crankcase. This would explain the slack primer bulb, high fuel consumption, and sooty plugs.

 

[JT!]

Re: 1971 Evinrude 50 - sudden power loss

thats a very interesting perspective jimmy i will check that first thing in the morning.

do you think its the entire cause of my issues, or just a contributing factor?

 

[JT!]

Re: 1971 Evinrude 50 - sudden power loss

a dead plug!