Alright guys, here's the situation:
I just purchased a 1974 Glastron 15ft with a 1971 Evinrude 85hp outboard and took her out for the first time a couple of days ago. Upon launch, it started right up, and with 6 people on board cruised around 30mph for maybe 15 minutes before it started "bogging" down. It picked back up in speed after a few minutes and then we came to a stop in a cove and floated for maybe another 15 minutes. When I tried to crank it back up, I got no fire. I continued to prime, choke and crank (in a revolving fashion) until the battery itself went dead without ever starting back up. We were lucky enough to be close to the dock and got a short tow in...
My immediate assumptions were:
A) The battery had insignificant voltage to provide spark.
B) The gas that came with the boat and that I was running was either a bad mix or had been sitting long enough to become varnish and quickly caused immediate clogging or fouling of the plugs.
So, yesterday, I recharged the battery (800cca) to full capacity, switched lines to a brand new 50:1 mixed tank and it once again fired upon first crank. Once I set out on the water, though it wouldn't run above 5mph or so and quickly died, leaving us floating in yet another cove. Luckily, I brought the trolling prop with me and we putted back to the dock.
I busted out the tools at this point, pulled the plugs, and found that they were NGK "surface discharge" plugs and, without a gap, made it somewhat difficult to tell whether they were acceptable. They did have a light black covering on them, though, so I suspect this to be the issue.
My plans now: Replace the plugs, clear the lines, and try again.
My question is: Am I a complete moron to suspect this to be such an easily fixable problem or is it likely to run much deeper? Should I even waste money on plugs at this point or should I perform further inspection? Any suggestions would be great and YES, I am a noob to outboards so feel free to put me in my place.