Wow – 2 posts in one day – that must be a record or something.
One of my jobs this weekend was to get my Atomic Bomb (Atomic 4 Gasoline Marine Engine) running properly. When we moved the boat from our winter slip over to our summer slip, I noticed that I could not get the engine over about 1200 rpm. It should hit 4000 easily. Of course, I left that problem until I really needed the engine – like this weekend when we wanted to go sailing. Here is what I found.
The engine idled well – or I should say it seemed to idle well. But when I put the boat into gear and revved her up, the engine would begin to bog down and would not go above 1200 rpm. So…
I made a couple of assumptions: I doubted that the prop was fouled as we have not been out anywhere where it could have picked something up. I also assumed the gasoline was OK as it would run in a seemingly normal fashion at idle – certainly not rough anyway. So I decided to check to see if it was my electrical/ignition system. With the engine running I removed each spark plug wire one by one and determined that this here A Bomb was only running on 2 cylinders. Removing wires 1 and 4 made no difference to how the engine was running but removing 2 or 3 would almost stall the engine. So now I had narrowed it down to 1 and 4 – but what was actually happening with them?
Next I pulled the wire off of 4 and positioned it close to the engine block and turned the engine over. The spark jumped strong and hard from the wire end to the engine block. I did the same thing with wire number 1 with the same result – there was good strong spark.
So, now I knew that at least the ignition system was good to the plug – the final thing to check was the plugs themselves. What I did was pull out plug number 4 and connect it to the wire – then placed it on the block so that the plug body was grounded and then turned the engine over – ah ha – no spark. Tried the same with number 1 and again no spark. So what we have is spark coming to the plug but no spark at the plug.
Fred Hawood, the original owner was kind enough to leave a set of used plugs in my engine bin. They were nicely wrapped in a baggie and tagged ‘Used 1998.’ So I eagerly ripped into the bag and replaced plugs 1 and 4 with these ‘used’ plugs and …. tada – we have a full power engine again. This Bomb had 2 bad spark plugs! I can only guess that the insides must have corroded over the winter – but that is just a guess.
Does anyone know how spark plugs fail? I don’t mean burn up, I mean fail – not spark anymore. They appear to be fine – not cracked – no carbon trails, just not firing. Anywho, if the weather holds out, we are off sailing tomorrow.
I hope you enjoyed this another episode of Marine Engine fun – by far the biggest headache I have with this boat: my Atomic Bomb.