Evinrude 25HP 1973 Fouled plug/white spark

[G DANE]

Working on brotherinlaws 25 HP. It keeps fouling plug on lower cylinder, causing cyl. not to run. After 1/2 hours of run it starts cutting out on cylinder. We have checked fuel pump. Plug is black wet and very soothy. Compression is fine-120 on both. Both sparks will jump 3/8 gap, only difference seen is that lover spark looked white- like ( hard to see in sunny day ) It got new pionts and condencers last summer. we tried to swap coils, but problem stays at lover cyl. When new plugs in, it runs fine for the first 1/2 hour to favorite spot. When it then gets restarted, It starts not running on lower ???? I tried to unscrew fuel pump and squese bulb, but pump didnt leak through vacuum hole.

 

[steelespike]

Re: Evinrude 25HP 1973 Fouled plug/white spark

G D are you saying the diaphram is good and fuel doesnt leak through into the pulse port?<br /> Manual says points should open exactly 180<br />degrees from one another, of course you need a fixture to check it.<br /> But be sure the points are at .020.and all <br />connections are clean and tight.<br /> If it has adjustable high and low speed mix<br /> screws give them a finetune.<br /> My personal theory is the lower cylinder runs slightly richer than the upper.and becomes more noticeable under adverse conditions.I may be<br />nuts but it sure seems that way to me.

 

[G DANE]

Re: Evinrude 25HP 1973 Fouled plug/white spark

Thanks for replying Steelspike.<br /><br />I did try to adjust l/s misture. With new plug in, it iddles like a 4stroke. Just fouls plug after half an hours of run, upper still looks like new by then. Can anybody tell mee, does white spark mean lower voltage, bad capacitor, though newly changed ??

 

[G DANE]

Re: Evinrude 25HP 1973 Fouled plug/white spark

bump - weather is great here and fish are biting, just not for us !

 

[Jack Shellac]

Re: Evinrude 25HP 1973 Fouled plug/white spark

G Dane: It's not unheard of for a new capacitor to be bad, but first I'd try a new spark plug wire. As the engine and it heats up, it may start arcing to ground.

 

[G DANE]

Re: Evinrude 25HP 1973 Fouled plug/white spark

Thanks for Idea - Plugwires are part of coil on this old stuff. We have tried to swap coils, but error stayed at lower cyl. It fouled plug so bad that it didnt fire at all, when we swapped lower/upper plug to see if it could run then. can the chrage coil be weak ?? If it was, shouldnt upper miss as well as lower ?? Really gives me headake.

 

[G DANE]

Re: Evinrude 25HP 1973 Fouled plug/white spark

I got a used statorplate today and put it on. discovered the points were some burned, especially on lower and cleaned them with 400 paper. Still cuts out now and then in iddle, but immediately picks up again. Surges when trottle is advanced under load. Will try to clean carb again and take a look at reeds. Compression was 112 exactly on both. Fuel pump pumps, i pulles hose and every piston stroke gives squirt af fuel.

 

[G DANE]

Re: Evinrude 25HP 1973 Fouled plug/white spark

we had it fixed today - it was a bad capacitor - runs amazing now, Thanks to all who replied to this thread.