old evinrude

[DazzaB]

Hi all
Just wondering if there are any mechanically minded guys out there who may have an idea about my 1975 25hp evinrude. I have no idea really about them and not really in a position to take it in to the mechanics to get it looked at so I thought i'd ask on here. After fixing my trailer issues a few weeks ago I took the boat out and while driving it made a bang. It didn't sound explosive like fuel or anything, more a hitting or snapping noise, but not like I hit something in the water. It ran fine for the rest of the session on the water. 2 days later I took it out and it wouldn't start at all. It revved very shortly after about 4 pulls, then nothing again. Spark, compression and fuel seem to be ok. I tried it again at home and it did the same thing, a quick rev after about 4 pulls then nothing. Yesterday I thought I'd have another look at it but couldn't get it going. I found a bolt that was very loose at the back that holds the yellow plastic part that has an arm that goes towards the fly wheel area. I've posted a pic of it below. I tightened this with my fingers, made sure a spring under it was in the right spot and gave the cord a pull and the motor started to fire. It stalled a few times but once I had tightened the bolt properly I got the motor going. So I was a bit relieved, I ran it for a while, ran the fuel out of it and left it for an hour or so then tried it again. This time I couldn't get it going again and it still wont go!
Does anyone know what this part I tightened does and if it would actually cause the motor to go or not? I was at the point of just leaving it for a while till I could get some money to buy a new motor but getting it going yesterday makes me think I might be able to get a bit longer out of it. Any ideas?
And sorry if the pics seem sideways, I got no idea why this happens.
Cheers
Daz