starting is a mystery

[JohnnyRay]

I'm new to the forum. I have a 2000 175 Mercury EFI on my bassboat. It has started and run perfectly since I bought the boat 4 years ago. I took it out for the first time this spring and it started fine. I was on a 5mph lake and so it ran at idle. I shut the engine off and fished with my trolling motor for 3 hours. When I started back up to go back to the ramp it ran rough and quit and wouldn't restart. The next day I started it on my driveway using a hose for cooling and it ran fine. Took it to a unlimited-speed lake two days ago and it ran great. Shut it off and fished for 20 minutes and it started right up and ran great. Went back to the 5 mph lake yesterday and it started and ran fine until I went to restart it and it wouldn't run. It cranked and cranked but wouldn't fire. As I was winching it onto my trailer I noticed an oil slick the size of the boat had formed on the water. (I premix the oil, it doesn't have oil injection) Any ideas?

 

[iang6766]

If you're using a 50:1 mix it is probably too rich in oil for extended idle, the oil injection system reduces the mixture to about 100:1. Basically the engine is not designed to idle for extended periods with a 50:1 mix and builds up a lot of oil in the crank case and on the plugs. I can't explain why it would start on a hose the next day unless you cleaned the spark plugs.

 

[Docksidemarineservices]

2x on the excessive oil caused by Idling on a Premix two stroke.

2 stroke outboards always start easier on the hose, no back pressure in the tuner.

 

[JohnnyRay]

lang6766 I forgot to mention that whoever owned the boat before me removed the oil injection system and I've been premixing since I bought the boat 4 years ago.