1975 Evinrude 50hp running rough

[starcraft_guy]

I have a 1975 evinrude 50hp it will start, idle and go about 2.5mph all day long but when it comes time to accelerate it, it wont even plain out. It always starts right back up if it stalls out. I took it out for the first time last week and it planned right out perfect then i trolled around for about 3 hours at 2.5mph and went to open it up on my way back in and it wouldn't plain out or get above 10mph. I cleaned the fuel filter and went threw the carbs and everything checked out fine. I also changed the plugs. Anyone have any info on what my problem is??? Thanks in advance.. Neal

 

[Daviet]

Re: 1975 Evinrude 50hp running rough

Have you checked the spark and compression?

 

[starcraft_guy]

Re: 1975 Evinrude 50hp running rough

Have you checked the spark and compression?

Ive checked the spark it looks good. I havent shecked the compression with a tester yet but i put my thumbs over the holes and push and it blows my thumbs off..

 

[Daviet]

Re: 1975 Evinrude 50hp running rough

IF the spark will jump a 7/16" air gap and the compression is at least 125 and within 10% of each other try a couple of things.
Use an inductive timing light and check the spark on each plug wire when it is acting up, should have constant flashes, no skipping.
Remove the air silencer cover and squirt some fuel mixture into each carb and see if it runs properly.

 

[starcraft_guy]

Re: 1975 Evinrude 50hp running rough

IF the spark will jump a 7/16" air gap and the compression is at least 125 and within 10% of each other try a couple of things.
Use an inductive timing light and check the spark on each plug wire when it is acting up, should have constant flashes, no skipping.
Remove the air silencer cover and squirt some fuel mixture into each carb and see if it runs properly.

Ok Sounds like a plan. What if it doesnt run properly when I squirt the mixture into the carbs? What does it mean?

 

[Daviet]

Re: 1975 Evinrude 50hp running rough

If the engine runs properly when you squirt fuel into a carb, you have a carb problem, the carb is not metering fuel to the engine.
If both carbs are operating properly it will try to flood the cylinder for a second.

 

[starcraft_guy]

Re: 1975 Evinrude 50hp running rough

If the engine runs properly when you squirt fuel into a carb, you have a carb problem, the carb is not metering fuel to the engine.
If both carbs are operating properly it will try to flood the cylinder for a second.

I can manually choke the motor and it will stall out. Is that the same thing?

 

[Daviet]

Re: 1975 Evinrude 50hp running rough

No, when you manually choke the engine you are doing both carbs at the same time, you need to do one at a time to isolate the carbs.
I guess you could remove the choke linkage and try choking one carb at a time, but it is not hard to remove the air silencer cover.

 

[starcraft_guy]

Re: 1975 Evinrude 50hp running rough

ok. I will have to try these things. Im really hoping i dont have a bad cylinder. It runs really good at low rpms and on the hose but put on a load it wont go. It did once but thats it.

 

[skipper711]

Re: 1975 Evinrude 50hp running rough

starcraft_guy, I have a thread Titled "Advice", I am trying to find the exact year of my 50hp, I have just put a couple of pics on would you mind having a looksee and tell me if they match please?