first tach then motor goes screwy

[uwboater]

I spent a good 2 hours on the water without problems the other day then decided to head back in. I ran the 1978 115hp Evinrude at about 4000rpm then gave an extra throttle to 4500. Suddenly I heard it "pop" a couple times then the tach was bouncing around zero. I backed off the throttle and the tach never recovered. Soon after, the motor started to bog down and loose power. At the dock I tried giving the motor gas in neutral but it sputtered a bit and never quite screamed like it used to. The boat has a brand new power pack and coil in one cylinder. what caused the tach to go screwy and could that have an effect on the motor? Other ideas?

 

[ob]

Re: first tach then motor goes screwy

First thing I would do is perform a spark test.

 

[Hooty]

Re: first tach then motor goes screwy

In some cases, a shorted rectifier can cause problems with the charge/trigger coils. Disconnect the rectifier and see if the ignition returns to normal.<br /><br />c/6<br />Hooty