1975 25hp Evinrude won't stay running.

The motor sat up fpr a while and then wouldn't start. I cleaned the carb, changed the points, changed the fuel pump, and changed the water pump. After all that it would crank (sometimes) but die after a few seconds. I let it sit a year longer. This time, I changed the fuel pump (again) and completely rebuilt the carb with all new innards. Exact same symptoms. Will sometimes crank and will only run several seconds then die.


Any ideas?

Re: 1975 25hp Evinrude won't stay running.

Check compression first off. Then if that is good, try squirting premix directly into the cylinder and see if will fire on that. That will tell you if your problem is fuel delivery. If it wont fire check to make sure your spark is good.

Re: 1975 25hp Evinrude won't stay running.

Pony said:

Check compression first off. Then if that is good, try squirting premix directly into the cylinder and see if will fire on that. That will tell you if your problem is fuel delivery. If it wont fire check to make sure your spark is good.

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Compression is great. And as I said in my earlier post it will run for several seconds then die (so it must have spark.) It has a new tank, new fuel line, new fuel pump, new fuel lines between plugs, pump, and carb, new needle and seat, new float, etc.

Re: 1975 25hp Evinrude won't stay running.

Have you tried continuously squeezing the bulb on the fuel line to see if that will keep it running?

Re: 1975 25hp Evinrude won't stay running.

BoatBuoy said:

Have you tried continuously squeezing the bulb on the fuel line to see if that will keep it running?

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Yes. I also forgot to mention that it would backfire every once in a while when the rope is pulled.

Re: 1975 25hp Evinrude won't stay running.

A couple suggestions were made to me conserning the symptoms:
1: Check the timing.
2: Check the surface where the case halves mate for leaks.

Either one of those plausable?

Re: 1975 25hp Evinrude won't stay running.

I know your problem. It is air intake. Check to make sure that there is sufficient air coming in! Try taking off the air filter completly, and starting it then. If it runs, put back the air filter slowly. When you start putting it back, you will feel the differnece, by the sound of engine. It may die once you put it back completely, again. Repeat procedure til the engine stays idling. Thank me later.

Re: 1975 25hp Evinrude won't stay running.

vdubber87 said:

I know your problem. It is air intake. Check to make sure that there is sufficient air coming in! Try taking off the air filter completly, and starting it then. If it runs, put back the air filter slowly. When you start putting it back, you will feel the differnece, by the sound of engine. It may die once you put it back completely, again. Repeat procedure til the engine stays idling. Thank me later.

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Only one problem..... It doesn't have an air filter. Only a spark arrester that offers no resistance at all.

Re: 1975 25hp Evinrude won't stay running.

Okay, the 25 has points that will change gap when the magneto plate vibrates due to wear. The top crank seal also leaks a gas/oil mix. R&R the flywheel, clean off any oil residue with carb cleaner, reset the points properly, but use a matchbook cover (clean) to set the points. That'll accomodate any slop. Pull the carb again. This time when you clean it, soak it in a sonic cleaner if you have access to one. Remove the welch plug on top of the carb. Make sure the tip of the low speed needle hasn't broken off in the hole. Make sure you can run a fine wire up the thin tube in the center of the main tube that goes up through the venturi. Make sure the fixed main jet is clean, and you can see through it. After all that, there's no reason it shouldn't run.

Re: 1975 25hp Evinrude won't stay running.

thanks, I'll try that.