1979 Evinrude 25 hp tiller

[PikeSlayer]

I looked at my carb. The parts all appear to be right based off the parts drawing. I included some pictures. The first 2 show the carb with the choke in the normal position:
https://i1052.photobucket.com/albums/s450/PikeSlayer83/GEDC0353.jpg.
https://i1052.photobucket.com/albums/s450/PikeSlayer83/GEDC0354.jpg
The 3rd shows the carb with the choke pulled out:
https://i1052.photobucket.com/albums/s450/PikeSlayer83/GEDC0355.jpg
4 and 5 are when pushing the choke to the full closed position and what it looks like when resting against the choke arm respectively:
https://i1052.photobucket.com/albums/s450/PikeSlayer83/GEDC0356.jpg
https://i1052.photobucket.com/albums/s450/PikeSlayer83/GEDC0357.jpg
6 shows the choke lever pulled out:
https://i1052.photobucket.com/albums/s450/PikeSlayer83/GEDC0358.jpg
7 shows the choke lever pushed in:
https://i1052.photobucket.com/albums/s450/PikeSlayer83/GEDC0359.jpg

You can see that the throw of the choke knob makes the choke arm hit the air box and therefore not actuate far enough. This still doesn't address the idle issue, but like jasper said, I need to take this one step at a time. Thanks in advance for any advice!
Pappy, I had this motor running perfectly when I first put the carb back on. The only thing I can think of is that something that I didn't get out of one of the passages broke loose and is now blocking something in the idle port. It had origionally idled perfectly, I could shift it in and out of gear, and throttle up smoothly in neutral. This was all done in a barrel though, not on the water. Now, with the airbox off, no matter what I do to the idle adjustment, it wants to die off. I get that applying choke would imply that it is running lean, but I adjusted the idle screw until the motor was smoking like crazy, indicating a richer than normal mixture, but it still wouldn't stay running...

 

[jasper60103]

Nice pics!
With the choke open (pushed-in), I'm almost positive the choke lever should push the bell crank. I can double check when I get home, but I think that's the problem. You just have to remove the lever and reposition it if that's the case.

Also, I think pappy was just trying to get your idle problem resolved. I respect his advice.

 

[PikeSlayer]

Thanks. Yah, if you think I just need to reposition the lever, that probably makes sense. Also, I hope I didn't come off as being upset or disrespectful towards Pappy. I was just trying to clarify my problem. I get what he is saying about the idle adjustment, I'm more just checking to see if you guys agree with me, and I should take the carb back apart and reclean it since it had been working perfectly, and now it isn't idling.

 

[PikeSlayer]

So how exactly do you reposition the choke lever? I'm worried that adjusting the linkage on the side of the carb for the choke will effect the way the throttle plate opens when you use the choke.

 

[jasper60103]

So how exactly do you reposition the choke lever? I'm worried that adjusting the linkage on the side of the carb for the choke will effect the way the throttle plate opens when you use the choke.

Pike,
I'm going by memory here, but it requires a little patience and dexterity. You are not making any linkage adjustment by doing this.
You'll have to remove the screw and washer for the choke lever. Then re-attach the choke lever such that the arm extending upward is behind the bellcrank. I'm not sure about this step, but you may have to push and hold the bell crank forward (because its spring loaded) to accomplish this.
When you get to this point, it will start to make sense. I wish I had some pics of mine, but I didn't get a chance to look at last night.

To answer your other question, checkout the youtube video below. Notice how he is moving the throttle and it doesn't affect the choke.

https://www.youtube.com/watch?v=8uhNenO6aIQ

 

[PikeSlayer]

I guess I'll just have to dig in and give it a try. Also, I'm guessing a re-clean of the carb may be in order. I just can't figure out why it doesn't want to stay at idle now...

 

[PikeSlayer]

I looked a little closer at the linkage from the choke pull knob to the choke plate linkage and it looked like it was a bit bent and tweaked from previous use. I did a little creative adjusting and got it to where the choke plate closes fully and the throttle plate opens slightly upon fully pulling out the choke knob. Then I took apart the carb and cleaned it again. I didn't see anything specifically come out, but there were a few very small particles floating in the carb cleaner when I was done. I put her back together, fires right up and idles with the airbox on. I still need to do a little more adjusting to get the idle right where I want it, but it runs, idles ok, and will stay at a low enough idle for me to shift in and out of gear. I just didn't get it to idle great with the throttle all the way on the idle stop cause it was getting late and I had to shut her down. Thank you all so much for your help! The advice and motivation/confirmation of ideas helped me to get through it without giving up. I will be creating a new thread shortly about my brother's Merc 9.8 horse 2 stroke that runs and idles, but won't carry a load in gear. I told him I'd take a look at it after I got mine worked out. Thanks again guys!

 

[jasper60103]

Hopefully, you'll get the idle just right when on the boat. Thanks for the update.

 

[PikeSlayer]

AHHHHH!!!! I got the idle great in a barrel, took the boat out yesterday and the motor absolutely SCREAMED across the lake! It was awesome for about 2 minutes, then it started missing a bit, running rough, and I had to throttle it back because it bogged down so bad. I tooled around with it for a while and it continued to run somewhat rough and it seemed to run a little bit better when I backed just off of full throttle. We anchored, fished for a while (about an hour) and I started the motor again. The return trip it ran much better, but still not as fast as the initial run when it was cruising. I made sure to tool around and took my time getting back to shore to see if the motor would run differently once it was warm. It ran smoothly for the entire trip back, but again, it wasn't as fast as the initial run. Any ideas? I don't want to screw with it too much because it at least pushes my boat through the lake, but I got that little taste of what it could be and now its haunting me :?

 

[PikeSlayer]

I pulled the plugs this evening. I know its been a couple days since I ran the motor, but the brand new plug I installed right before running, are already kind of fouled looking. There is some caked on crap. I don't really get how it could be fouled already unless it's running rich right? I have the idle dialed almost a third of a turn leaner than the recommended starting point. Is there any way to adjust your full throttle mixture? Could this be causing my issue?

 

[bigwave]

Hey Pike this may be a silly question. Did you use new gas on your trial run, and is you mixture of oil correct for the engine? I once over mixed my fuel/oil, fouled my plugs real quick, boat ran like crap. I changed the plugs and gave her fresh fuel and she ran like she was supposed to. This is a cool thread, I am learning through your problems.

 

[PikeSlayer]

Yah, it was fresh gas, and a new tank when I did it. Brand new, 50:1 mix. At worst, I mixed it ever so slightly lean. So I don't think its a fuel mix, but thank you for throwing ideas in to keep the mind running. Good thought!

 

[xbacksideslider]

It might have got hot on that initial run when it "screamed" across the lake.

How's your compression now?

 

[shawnfish]

probally a dumb question, did you adjust both of the idles? i had the same problem with my 80 j25 after removing and cleaning carb and just played with the low speed needle(front of carb through the silencer) and didnt get it right untill i used a tach and adjusted the one at the base of the tiller and the low speed needle....5450 rpm's and mine was singin!..........

 

[PikeSlayer]

I took my boat back out yesterday for its second trip. The motor ran good cooking across the lake right away. I still don't think its running as well as it did for my very first time out, but with 2 adults and 3 kids, the boat did push along at a decent clip. The problem is, after sitting for about a half hour, I started up and when I cranked up the throttle, it just surged and didn't really want to run above 1/3 of throttle travel. Shut it down, fished some more and then fired it up, ran good again. Sat and fished some more, then took a run across the lake. The motor would run good for a couple minutes, then start surging and loosing power, if you dropped to idle for a few seconds and back up, it would run good for another minute or so before surging again. I started pumping the bulb while cruising and notice it was getting soft. When I continued to pump the bulb it smoothed out some. After sitting and fishing for awhile, the return trip across the lake I didn't have to pump the bulb at all, and it ran for the most part fine the entire way. I do notice around the time it starts to surge a bit, before it surges badly, if you back the throttle off just a touch from wide open, it actually increases RPM a bit. Could it be that the fuel pump is weak and not keeping the bowl full of fuel? I was wondering since with the motor running at idle for a bit, it will run higher rpm again for awhile, like maybe the slower speed allows the pump to catch up a bit? Any ideas would be great guys.


P.S. I have not checked compression yet. I need to get my hands on a reliable tester.

 

[PikeSlayer]

probally a dumb question, did you adjust both of the idles? i had the same problem with my 80 j25 after removing and cleaning carb and just played with the low speed needle(front of carb through the silencer) and didnt get it right untill i used a tach and adjusted the one at the base of the tiller and the low speed needle....5450 rpm's and mine was singin!..........

Where exactly is the other needle? I'm wondering if that might help it out a bit. The problem is, if I look on youtube, I can find guys with the same motor cruising across a lake and they look like they're going a lot faster and their RPM sounds higher. I'm sure some of this has to do with the weight of the boat, and maybe I'm being too picky, but I really like to go fast! 8)

 

[Johny25]

Surging indicates a fuel delivery problem........ can be several things, float not set correct in the carb, weak fuel pump, clogged fuel pump, high speed orifice in the carb clogged, fuel lines sucking air, carb base gasket leaking, fuel tank vent hose not working.

If you pump the ball on the gas tank and the engine runs better then 99% of the time it is a weak or faulty fuel pump. If not then I would clean carb good and flush lines to be sure they are clean.

 

[PikeSlayer]

Surging indicates a fuel delivery problem........ can be several things, float not set correct in the carb, weak fuel pump, clogged fuel pump, high speed orifice in the carb clogged, fuel lines sucking air, carb base gasket leaking, fuel tank vent hose not working.

If you pump the ball on the gas tank and the engine runs better then 99% of the time it is a weak or faulty fuel pump. If not then I would clean carb good and flush lines to be sure they are clean.

I had the carb apart and cleaned thoroughly. I had also flushed the lines as I reassembled everything. The fuel pump is the only thing I didn't mess with. I haven't been able to find a rebuild kit for the fuel pump. It looks like you have to buy an entire fuel pump assembly for about $60. I just wanted to bounce this off you guys before I spent the money on it. Hopefully a new fuel pump helps with the problem. Thanks for your help!

 

[PikeSlayer]

I just ordered a fuel pump and will hopefully have it on and tested within the next week. I think what I will do the next time I have the boat our is try and take a quick video of it running to see if that offers any additional info for you guys. Thanks again for all your help. God I hope this works.........

 

[PikeSlayer]

WOW! So here is the conclusion. I got my new fuel pump, went out and got new fuel and vacuum lines. I decided to take off the carb to make it easier to replace some of the lines. When I pulled off the airbox, there was a huge chunk of foam from the upper cowl insulation stuck around the main jet and jammed in the throttle plate. I CAN'T BELIEVE MY ENGINE EVEN RAN WITH THAT IN THERE!!! Needless to say, I already had a new pump and lines, replaced all and took it out yesterday. RUNS LIKE A CHAMP!!!! 8) Thanks for all the help guys!