Surging idle

[BRIELLY]

I just put the boat in the water today. It was idling fine in the driveway and was idling good at the ramp but then it just died. When I restarted it it kept on surging up and down. It would smooth out for a few seconds and then start surging again. I took it home and went through the carbs but they were perfectly clean. I'm thinking maybe this is an electrical issue? Its a 91 merc 35. Anyone have any pointers or trouble shooting techniques to get me started? Thanks

[captpete13]

check the fuel pump. unbolt it from the block but leave all the hoses connected. Squeeze the primer ball. If any fuel comes out from the back you have a bad diaphragm. The leaking fuel goes directly into the crankcase causing erratic idle. It would also run kind of rich. If thats not it I believe that motor has an idle stabilizer module on it. It manipulates the timing to achieve proper idle. Use a timing light to see if the timing is all over the place. If you disconnect it and it idles steady then it is probably bad.

[Bonita Dan]

Check your fuel filters for water. Its an easy first step before beating your head against a rock tryin to find out whats wrong. Mr.Ethanol is just killing us here in the south so I imagine its gotta be the for yall.

[BRIELLY]

This afternoon I ran it off a seperate tank of gas and its still surging. I also tried unplugging the idle stabilizer and checked the fuel pump. Still no good. There seems to be a very large amount of oily gas leaking from the carbs when I tilt it up. I realize there should be some leaking from the carbs but when it forms a puddle in the splashwell it seems too much. This was happening before the idle problem appeared but could it be related and what would cause this to happen?

[captpete13]

are you sure that you set the float heights correctly on your carbs? Have you checked the fuel pump yet? It really sounds like that could be it.

[BRIELLY]

The floats were perfect. I took the fuel pump off and squeezed the bulb and got no gas out of the back. I even took it apart and checked but everything was good.