1971 25hp Evinrude running issues

[1970Mach1]

I have a 71 25hp Evinrude I've been working on. New seals lower unit. New carb kit. Checked the points. 125psi compression. New plugs. It will run for a bit but if you pump up the ball it will start to die out. If you leave it alone it will start coughing and want to quit. I can't get the idle screw to fix it. What do you set the float to? I just made it level with bottom of the carb. It almost seems like maybe the float level is to high. How do you check if t
he fuel pump is working properly?

Oddly enough the engine looks like it has little time on it, even when I had the lower unit apart the clutch dog has no wear at all. Shift fork looks like they never put it in reverse either.


Thanks for any ideas...

 

[racerone]

Inspect diaphragm on the fuel pump.

 

[F_R]

Agreed, the diaphragm is suspect. Easy no-cost check is remove the fuel pump from the motor, hoses still attached. Then give the squeezer bulb a squeeze. If gas squirts out the backside of the fuel pump, the diaphragm is the culprit.

 

[1970Mach1]

What does this hose do that looks like it's coming from the bottom of the manifold? Should fuel spray out of it when running?

 

[racerone]

Fuel sprays out when motor is running.----It has been suggested you inspect fuel pump diaphragm.---What have you doone there ?---Was it OK when you had a look at it ?

 

[1970Mach1]

So fuel should should be spraying inside that hose?

 

[1970Mach1]

Ok so I had a aftermarket fuel pump on it yesterday. When I ran the engine last week it was acting like the pump wasn't working and the fuel ball would empty. Anyways I put the old fuel pump back on and if you pump up the ball no fuel comes out the hole in the back.
I had it running for half hour or so in the can. It's got kind of a rougher idle than I would think it should have. Every once in a while it would slow down and buck a little. You can idle her up a bit and it will be fine for a while. If you shift her in gear and give it some more throttle it seems to run real rich till you rev her up a few times till it clears up. Smoked like crazy when you do that. Where should the throttle be set on the carb when the tiller is on start? Whoever had it before had the throttle adjustment half way on just on idle.

I've seen some fuel laying in the carb when I was trying to start it. It won't start with choke all the way when I was trying to start it also.

 

[1970Mach1]

I took the fuel line of from the fuel pump and it intermittent sprays, didn't take long at all till the engine quit.

I put a harbor freight temp gun on the cylinders. It was at 135°F after running a while I saw it around 110°F also.

 

[1970Mach1]

Here is a short video clip of it...


https://youtu.be/OHc-pzEGKtA

 

[1970Mach1]

Top plug always looks clean too

 

[racerone]

It is running on one cylinder.----Pull flywheel with a 3 bolt puller in those 3 threaded holes ( 1/4-20 ) ---Inspect coils, they will be cracked or a new set has been installed.----Spark should jump a gap of 1/4" with ease.

 

[1970Mach1]

I just had it running and pulled the bottom plug wire. The top clean looking plug keep it running on 1 cylinder. I had the flywheel off yesterday and both coils look good with no cracks.

 

[1970Mach1]

It does run better on the bottom cylinder when the top wire is off then running on just the top. Just curious but could the top not be getting fuel?

 

[1970Mach1]

I'm at a loss what to try? Should I swap coils and see if the top cylinder runs better? I see spark on both...

 

[1970Mach1]

Oh forgot to ask... is that ground wire supposed to go there (second picture) seems like a goofy spot when you throttle up its pretty much stretching the wire.

 

[racerone]

Does spark jump a gap of 5/16" on both leads , yes or no ?----Checked the reed valves ?

 

[1970Mach1]

I had a 18hp coil I tried in it. Didn't change much. Tired a new point set on the top cylinder. Didn't change much. Tried a used condenser. Didn't change much. Put the old condenser on the bottom cylinder and bottom cylinder condenser on the top. Didn't change anything.

I put it on a the boat and test ran it. It bogs in mid range then clears up and runs fine wide open.
Any ideas now?

https://youtu.be/4j2L2pcR-hU

 

[1970Mach1]

I couldn't find my clip on spark tester. I used a old plug and made the gap pretty wide. It did jump that. Any suggestions on a way to test a 5/16 gap?

I looked into the intake at the Reed valves, nothing blocking any open. How do you check them?

 

[werewolf]

i have two of those, a rude and a johnson, i had to replace plug wires and the wires for the points, started cutting out about 3/4 throttle one day, made the wires longer to allow for movement, ,,, runs great now it did the exact same thing with the plugs .

 

[1970Mach1]

I ordered OMC coils, points, condensers and plug wires for it. I'll rewire it too, the wires to the shut off are pretty bad. Thanks for the tip!