Low compression in port cylinder 3 optimax 250 dfi

[Ironmikea]

I have a 2004 utopia 205 with a optimax 250 dfi. I bought it from a friend of a friend in April. The boat had been setting in FL for a while so I didn't have high expectations. The motor did crank and run though. I've done a lot of work on inboards so I do have some motor knowledge. No work on outboards though. Here's the question. I did a compression test on the cylinders and this is what I read was the following: port side 1) 90 2) 100 3) 80, starboard 1) 100 2) 95 3) 100. I sprayed foggy oil in the lower reading cylinders (80, 90), but the didn't change. I know the "experts" state that they should be within 10% of each other so it appears that it's a problem with port side 3. Would you suggest rebuilding or replacing this engine? I know some would just fix the one cylinder but I guess you would disassemble the whole engine and evaluate? Is the any information that can be obtained through diagnostic equipment. I had considered taking it to someone but I believe they would have first done the compression test and cam to the same conclusion. Thank in advance for your response.