Hey everyone, I have been lurking this forum for quite sometime but still can't figure out what's wrong with my 1973 evinrude norseman 40hp outboard. The motor had been sitting dormant for approximately the last 14 years after the floor in my 73 Peterborough jet star had rotted away. Last year I finally had a new transom and floor put in the boat, although the guy who did it put some cracks right through the Fiberglass trying to get the old rusted screws out of the trim. Anyways, I put it in the water and couldn't get it to start after changing everything but the electrical. I then took it to a marine place down the road from the cottage where they replaced all the electrical components. Got it back and the motor started, although now if I revved at around half throttle or a bit more in neutral the motor would start running away and start hiccuping and wouldn't throttle down when the butterfly valve is closed. When it does this I turn the key off and it kills the motor. So other than that the motor seemed to run ok at full throttle for a while. About a week later I'm half way across the lake and a cylinder drops out on me. After narrowly making it back to the cottage I haul out the boat and take it back to the place who fixed the electrical. When I get it back I asked what was wrong and he says something about a loose ground connection or what not. So I put it back on the water for a bit and now when I get it up to 3/4 or higher on the throttle the motor starts shaking like crazy like its misfiring or something. The motor would seem to settle down a bit and smooth out after it warmed up for 20 minutes or so. Sometimes you would gun it and it would shake for a couple seconds and then smooth out again. Also, at times it would be running smooth until you took a sharp turn and it would start shaking again. I also noticed when you would slow down quickly and come off the plane it would make an awful growling sound that I guess I would describe as ventilation or cavitation? Despite my better judgement, I continued to run it this way for the remainder of the 2014 season. Fast forward to the beginning of the 2015 season and lo and behold she won't start again. Some mice did get under the hood in the off season but I didn't see obvious damage. I decided to just redo the magneto plate again with all brp components. At this time I did notice there was no continuity between the magneto plate and the power head which I thought was strange. I then noticed that there was a wire that was tie wrapped and connected to the power head that appeared that it was at one time secured to the mag plate for a good ground connection. I ended up reattaching this wire to the magneto plate to ensure a solid ground to complete the circuit. Finally got the boat back in the water near the end of this season and got it running but still had the runaway problem when revving a bit in neutral and still have the motor shaking at 3/4 throttle and beyond. Again, if the motor is allowed to warm up for at least 20 minutes I can get it to eventually smooth out a bit but obviously somethings not right. I believe the boat is heavier since it was redone which if anything would just put the prop lower in the water. I've considered everything from an misfiring problem to a spun prop to ventilation issues but have done nothing but confuse myself. I haven't actually marked the prop yet so that could still be on the table? I just find it strange all these problems happened at once so I figured it's all related? I also suspect the first time I got the motor back that the ground between the magneto plate and power head was connected and the second time they decided to leave it disconnected and that's what he was talking about when he said a loose ground. The fact the motor works slightly better when it warms up and gets rid of the misfire problems may also offer a clue to what's happening? Maybe the grease the mag plate is sitting on is insulating it a bit from the power head but as it warms up the grease thins out a bit allowing a better connection? I have no idea at this point. I take it a spun prop wouldn't cause intermittent bite problems, it would either bite or completely fail? I uploaded some videos on YouTube to help diagnose the problem and perhaps the members here who are far more experienced than myself will be able to definitively tell me what the problem relates to. I appreciate any help you can give me, thanks!