1999 merc 115 oil reservoir cap

[itspossible]

I have a 1999 2 stroke 115 hp with an oil reservoir for injection. I'm not sure about the cap with the dipstick, it doesn't seem to have any thread on it. Is it supposed to just turn 1/2 turn until it snugs up a bit or is it supposed to screw in so the o ring gasket compresses to seal it? I have to use a pair of pliers to remove it since it's kind of wedged in there.

 

[Texasmark]

I had a 90 of that series engines. I forgot but you can find out. The cap has a couple of locking tabs, right? Look in the tank where the tabs will be after you insert the cap. If you see a sloped exit from that area then yes it pulls down on the oring as you twist it CW. That's the only thing that makes sense. To just have a slot with a straight sliding area and twist till it abruptly stops, relies completely on the durometer rating of the oring at the time. Over time it will soften up and you will lose you seal. No body answered so I took a shot at it. If I still had my boat I could give you a better answer.