Fouling spark plugs 135

[741violin]

135 horse '74 Evinrude, the top two spark plugs foul out immediately. I was wondering, is it electrical or carb?

 

[iwombat]

Re: Fouling spark plugs 135

Most likely carb. Check the choke plates on the top carb, make sure they're opening all the way.

 

[Randyg123]

Re: Fouling spark plugs 135

By immediately, how quick is that? How does the engine run otherwise? Are they fouling after a short time idling around or on the muffs?

What about tooling around for a while at high rpm only. Are they fouled then?

what do the bottom two plugs look like under after idling and high speed?

Since the top carb affects the top cylinders, it sounds like a carb issue most likely.

 

[ezeke]

Re: Fouling spark plugs 135

As Iwombat said, the choke system on the 1970's V4 motors had problems that sometimes need correcting. Run the motor with the cover off the carburetors long enough to be absolutely sure that the choke plates are wide open (horizontal) as soon as the engine warms up.

If the choke solenoid still has the two positive purple wires connected to different posts on the terminal block, you may want to change it.

By now the fouling will be throughout the firing chambers on those cylinders, so you may want to do your annual de-carbon treatment now.

 

[tashasdaddy]

Re: Fouling spark plugs 135

have you checked the spark on those cylinders, taken a compression check on all 4 cylinders, are they equal within 10%?

 

[741violin]

Re: Fouling spark plugs 135

Thanks for you input. The top 2 plugs foul out immediatly.I have put it in the water only to find out that when I put it in gear it stalls. The plugs appear to have oil only on them the gas is gone. At first I thought it was coils, but it seems to coincidential that it was just the top 2. When I had it in the water I let it run for about 15 minutes to make sure it was warmed up, but as soon as I put it in gear it stalled.

 

[741violin]

Re: Fouling spark plugs 135

What would I use to check the spark? Is spark tester something I can buy at a boat store? In my catalog it shows a spark tester for all 4 at once. Is that right?

 

[ezeke]

Re: Fouling spark plugs 135

If you want to do a good test of spark on the running motor, use a inductive timing light. It has fingers that wrap around the spark plug wire. The light will let you "see" the spark or lack thereof, and you can tell if it is firing erratically at different speeds.

If you want to do a static test, you need all of the plugs out cranking at 300 RPM and a tester that can be set to allow a spark to jump 7/16".

This one is sold here at iboats.; search the marine store for spark tester.