1988 90 hp v4 plugs

[moonman]

Motor hasn't been running good. I have replaced plugs, plug wires, coils, tried spraying carb cleaner through carbs, put seafoam in gas tank and I am only getting 2800 rpms at WOT. Just ran it for about 15 min in my driveway, then checked compression and got 120 on all 4 cylinders. Pulled the plugs to look at them and 3 looked the same, a little dirty and fouled. The other was bright and shiny and looked like it had been touched up on a wire wheel. Tried to post pics from phone but it says file is too large. Not very tech savvy. Wondering if carb might be completely blocked or perhaps that cylinder isn't firing? Gonna try spark test next, I guess. Any ideas?

 

[interalian]

Yes, check spark - should jump 7/16" with a bright blue snap.

Also, check the carbs in case you're getting no fuel to that cylinder. Bad things will happen quickly with a blocked jet in the carb.

 

[moonman]

No spark when I did the spark test on the plug wire going to that cylinder. Tested coil with multimeter and it was bad. I had just changed all of the coils in the spring because all of the old ones were cracked. Glad it wasn't anything more serious.

 

[interalian]

Good news. But bad news that new coils failed so quickly. What brand did you buy? I lost one original '82 coil this year and replaced it with another OE coil that I had from a parts motor.

 

[moonman]

I have to try to look it up where I bought the coils from. Thinking it was a Sierra part. Luckily, I saved a couple of the old ones. They have a couple little cracks in them but they both tested good. The new coils are probably like most things that you buy anymore......it is usually junk and doesn't last.

 

[moonman]

Got them on Amazon on May 9th, 2016. They were from Sierra International. 18-5179. $19.94 a piece. Think I have only had the boat out about 5 times. I guess it is the classic case of "cheaper isn't always better"!