Why would this happen

[steplift20]

First, 1988 150 hp Black max oil injection
I start my boat about once a week cause I changed the switch boxes and want to make sure it starts cause I had a issue last year so I want to start it to test it
She starts perfect don't even have to prime the bulb
I did this going on about two months just to check
Yesterday I when to start her and it was very hard to start,I think it was flooded with oil
I looked at the inline fuel filter and it was blue the color of the oil
I finally got her started,smoked very very bad ran for about 10 minutes to burn off the oil,never had this happen before
I started her today and perfect No smoke started right up started her twice And perfect, the only thing that I did before I had the problem was that I topped off the oil resivoure but that's all I did
What would cause the oil to flood the motor I'm stuck The only thing I could think of is that I think there is a one way check valve and maybe it got stuck open And let the oil flow I'm baffled .