1975 Evinrude 135 HP will not stay running

My engine model number is 135483-B and serial number J0003106. Engine is on a 1975 Browning Mustang II (18'). Some background... I have had the boat/motor for about 2 months now. Engine has always idled rough. Ran fine once it gets above an idle. Occasionally would lose power when running at WOT. The last time it did this was the last time it was running continuously. It lost power when I was pulling a tube, wouldn't start again, and had to get towed back to the dock.<br /><br />Now it won't stay running. Will fire after I choke it and run rough for 5 or 10 seconds, then sputters and dies. Cranking and rechoking it generally will make it run another short time.<br /><br />Since the problem on the water, I have had carbs off and rebuilt them, floats are level with the carb body when turned upside down (closed). I had reed box off and cleaned reeds - none bent or damaged, compression is 125 psi on each cylinder, new gaskets and hoses on everything... nothing seems to help.<br /><br />Also checked all 4 coils. Primaries are good. The secondary on one of them measured open with the meter, so I replaced it. Now all secondaries measure the same resistance. Sensors check ok. I have a strong blue/white spark at all 4 plugs. <br /><br />I see a pulsating stream of fuel from the fuel pump output with the hose to the carbs disconnected while cranking. However, the primer bulb goes soft after the engine starts. This is the case with each bulb, on the built-in and portable tanks (I don't think the pickups in the fuel tanks are clogged). I can pump the bulb up to the point where it's very firm, but once the engine starts running, it goes soft.<br /><br />I don't know if any of these symptoms mean anything together, but I'm really running out of ideas. I think my last resort is a new fuel pump. I think I got all the info I know so far in here... sorry for the long posting. Any help would be appreciated. Thanks!

Re: 1975 Evinrude 135 HP will not stay running

The way you can check for the fuel pump is while the engine is running pump the bulb and try to get it to high RPMs, then keep pumping it and bring it back to an idle... If while you're doing this, the motor stays running i'd say you have a bad fuel pump.

Re: 1975 Evinrude 135 HP will not stay running

Brett, thanks for the advice. I wish there was some other way to test it out, since I can't run it above idle with the flush attachment. I guess it might come down to putting it in the water to try it.