Guesses on what happened?

[MDPursuit2470]

Kind of a long story.... late summer this year I bought a Pursuit 2470 with 1996 oil injected carb'ed twin 150's with about 500 hours on each. I was told the ignition module was busted when I bought it and figured I would fix it over the winter. The port engine starts with the key but you have to run it in the off position otherwise it chirps every couple of seconds. To stop it I would have to choke it since the ign module is broken. Well, I was out running and felt the port engine start to bog, so I shut it off immediately and checked the prop to make sure I hadn't picked anything up. No problems with that, so I started it back up and it sounded terrible. Shut it off and checked under the cowling, and it had run out of oil! Both the main tank and the reserve were empty. Since the ign module was broken I had no alarms or gauges to tell me it was low but I did do a visual check on the oil tank every now and then (must have been seeing the stain thinking it had some oil in it.)

Any way went back to the pier on the good engine and pulled the plugs. Couldn't see any visible damage to the cylinder head so put some oil in it and fired it up. It still sounded horrible, like it was running on 4 or 5 cylinders so I shut it down and started kicking myself for being so stupid. Finally a month later I got the nerve up to go down and do a compression test. 115-130 psi all around. So I changed the spark plugs and fired it up and it ran fine. Took it out and ran it for awhile at high rpm's with no problem. It sounds exactly like the other engine. Came home and put an OHM meter on each of the old plugs and they all were showing the same resistance from the tip to the electrode, so I don't think any were bad.

So what happened, any guesses? Why didn't I sustain more damage, or did I, and it just hasn't shown up yet. Could it have been the plugs overheated as the engine heated up from the lack of oil and I shut it down before there was serious damage?

Interested to hear your thoughts/experiences on this.

[Bay Catt]

Strange things sometimes happen with outboards, and then as if it were an act of god they are just fine. Perhaps your low oil did have some adverse effect on performance,(didn't help any). But beings it sat for a month and I am assuming that the boat was docked and that the gas was settled when it ran OK, you might want to take a look at what has settled to the bottom of your gas tank. I pumped mine out recently with the siphon tube resting on the bottom of the tank and was amazed and the crap that came out. Black algea, water, and this white lumpy stuff that looks similar to lithium grease. Then I disconected the fuel line and ran engine till it stalled, put the fuel line into a fresh gallon of gas, started it up and presto. Within 10 minutes it ran like new. Cancelled the appointment with the boat doctor and went fishing. Now with this ethenol gas I only keep tank 1/2 full unless I am planning on burning alot. Let me know what happens.

[MDPursuit2470]

Well I drained the gas tank and the gas looked fine, put it in my truck and no problems. Ran both engines on land and did notice a slight tapping noise coming from the engine that ran out of oil. Maybe it did sustain some damage? I'm not sure that the tap hasn't been there all along. That engine always was the harder starting of the two and always smoked more than the other.