1975 25 hp Evinrude 25502B

[KC9000]

Hello got another project motor. 1 thing I have been stumped on. As the cam roller passes the fist dot on the throttle control the engine dies out. RPM's go down and it dies. At higher RPM's motor runs good. It should be able to go passed the first dot on that throttle control and continue to idle. With the throttle valve closed the engine dies. If I tweak it to where is stays open a smige it will idle pretty good, but I wonder what would cause it to not idle when throttle valve is closed? Hoping someone can save me some time... The carb has been cleaned with carb cleaned and AIR. I have 2 other motor from this Era and they can close that throttle valve and idle fine. I have adjusted needle acording to manual, seat the needle gently and one turn back out, it actually needed like 1 1/2 and it ran great when that valve was opened a smidge. As soon as it closed all the way it dies.....

 

[Crosbyman]

did you clean the top idle drip chamber under the round dime size plug.... idling requiers fuel flow via the top side of the carb .
the top drip chamber is fed fuel via the LS needle tip which itself is fed fuel sucked up via the side of the carb ( look for a small side channel leading to the top clean it, carb cleaner it, and blow it dry)

carb cleaner shot in the side channel should exit on top near the retracted needle tip

btw how is compression ?

see pic of old style carb..... see idle drip chamber same as yours on the 25hp

 

[KC9000]

I did clean that and re plugged it. The needle I turned back out 1 1/2 turns and it ran good with that valve opened a little. But as soon as it closes it dies. So it is set to the leanest setting possible. Any more lean I get the lean sneeze. So needle is set in a good spot.

 

[KC9000]

Here is a video, I'll post a better updated video tomorrow of the issue. Captured this before I changed a fuel line that was leaking air. It stopped surging after the new fuel line. At the end of the video I was feathering the throttle to keep it running and when it died I had it as far back as I have the idle screw set, the cam roller is just behind the first dot on the throttle control.

 

[racerone]

Check spark.----Might be running on 1 cylinder.

 

[KC9000]

I hooked up the timing light and had good pulse. But I will check spark for sure. I did replace a coil as it was split and not working. Tested the current ones and timed points In with the multimeter. But do you think weak spark at low rpm? Or bad coil when it heats up?

 

[KC9000]

Both look like this. Got good spark.

 

[KC9000]

This is from the other day, a better video.

 

[F_R]

Hello got another project motor. 1 thing I have been stumped on. As the cam roller passes the fist dot on the throttle control the engine dies out. RPM's go down and it dies. At higher RPM's motor runs good. It should be able to go passed the first dot on that throttle control and continue to idle. With the throttle valve closed the engine dies. If I tweak it to where is stays open a smige it will idle pretty good, but I wonder what would cause it to not idle when throttle valve is closed? Hoping someone can save me some time... The carb has been cleaned with carb cleaned and AIR. I have 2 other motor from this Era and they can close that throttle valve and idle fine. I have adjusted needle acording to manual, seat the needle gently and one turn back out, it actually needed like 1 1/2 and it ran great when that valve was opened a smidge. As soon as it closed all the way it dies.....

About those two other motors "from the same era"---are they the same year and horsepower?

Just for laughs, pull the drain hose off the upper bypass port cover and let it spew overboard. Idle better now? Gotta tell you this; that motor is idleing about as good as a lot of them did when brand new. We got a lot of complaints about them from owners that traded in their old 18-20hp motors which actually ran better than their new one. The problem is the early attempts at cleaning up the environment. If you remember, new cars also ran crappy during those years.

I know a way to make them idle better but cannot say what it was because it probably is illegal.

 

[KC9000]

Lol yeah. The other 2 are 73 18 hp and a 72 20hp so no not exactly the same. I will pull that recirculation hose off and see if it improves read about this a few different times. Recirculating that gas helps environment but messes With performance. Should I run a j6c plug think that will help? Got a j4c in now.

 

[KC9000]

Pulled that line and it did not make a big difference. The engine is still surging a bit. Any ideas with that? I thinking the carb is bad?

 

[racerone]

What are the compression numbers ?----Those carburetors are are elegantly simple to inspect / repair.-----Could be a broken carbon seal on bottom of crankshaft too.

 

[KC9000]

Yeah I was suspecting that too. Compression is 130/135. Plenty of compression. When I put the hood on it runs a little better. I am showing it tomorrow. I have it up for sale soo we will see what goes down. I had it to the best it was gonna be that last video I put up. Then I pulled the recirculation hose off and it broke and since then it has been a little off of that video. We will see what happens, I got it to the best settings since that video. It runs great at high rpm's it's when you wind it down, it just bogs out. I ha e looked at the carb a few times and all passage ways clean, been under the flywheel and cleaned and set points. New plugs and tested spark and it is good. Gotta be that lower carbon seal? What other symptoms would I see if that were the case? Unburned fuel mix in the bucket? There is a little of that....

 

[KC9000]

Well I took it apart today. Found that the drive shaft o ring was gone, water pump grommet was all messed up and broken, baffle gasket was gone, and the housing cover seal was gone. Assuming that was all bad, I am sure the carbon lower crankshaft seal is bad too. Before I order all the things I need to get this back together, think all that would cause I to not idle... and die when the throttle valve is closed? I found lots of sludge in the lower like you see in that exhaust chamber.

 

[KC9000]

So what needs to be done to get that lower crankshaft carbon seal out? What bolt do I loosen, the two on the side then what others, I think I read something about 3 bolts need to be loosened and then the seal will come out...

 

[F_R]

Huh?? Carbon seal is held on by the snap ring. I don't think that is the problem though.

 

[KC9000]

I will inspect it later today. Got new baffle gasket and carbon seal on the way. Gotta find a cover seal though, they are scarce.

 

[KC9000]

@F_R any ideas what could cause the dying when throttle valve closed? After taking this thing apart I know several things needed to be fixed, driveshaft o-ring, baffle gasket, water pump grommet, and I will replace the lower seal just for knowing it's done. Probably replace impeller since I am there. If all that don't help it I will swap carbs with the 25 electric I got on the bench. Same carb. Needed to make it right after digging into this motor. There was fuel leaking a little on the bottom of the cover due to the baffle gasket being disintegrated.

 

[KC9000]

Well that was easy. Clip spring and pulled the lower seal. Will update when she's all back together. Hoping for a good idle. There was some fuel on the top of the seal, so it could have been leaking. Rubber inside looked old and worn too.

 

[racerone]

The picture shows the bottom of the seal.----The working part of this mechanical seal is the other side.----Picture of it ?