How can i check the oil level in my bass boat? I cannot see the oil level at all .I know its not empty.I even used a flashlight.

Need to know year and make of motor. 2 stoke or 4 stroke? Motor oil or lower unit oil? 

Make sure you have the motor trimmed level.

Mine has a dipstick, yellow like a car 

Not enough information!

1999 Johnson 225 H/Output. It has a plastic reservoir in the battery

 compartment like the windshield washers on a car . I just can't see the oil level. ThankYou

11 hours ago, Ghostshad said:

1999 Johnson 225 H/Output. It has a plastic reservoir in the battery

 compartment like the windshield washers on a car . I just can't see the oil level. ThankYou

A lot of folks bypass the plastic reservoir and mix their own “just in case”

 

I would imagine that it will beep when the plastic reservoir is nearly empty. I would just keep some on board and make sure it’s always topped off 

I don’t know about your specific motor but on my 2000, 225 merc 2 stroke, the oil injection system consisted of 2 parts.  The remote oil tank in the bilge area and a saddle tank on the side of the motor.  The oil injection system pumped oil from the bilge tank to the saddle tank on the motor.  If the bilge tank ran low and subsequently the saddle tank was not getting filled, an alarm would sound.  You fill the bilge tank not the saddle tank.  Possible failures are a plugged filter in the bilge tank hose.  It periodically needs to be cleaned and a failure of the oil pump to pump oil to the saddle tank on the motor.  Generally speaking the oil injection systems were very reliable but some opted to pre mix oil and fuel directly in the tank.  This requires removing some injection equipment and plugging some vacuum lines not just adding the oil to the fuel.  

If you can't see the oil level inside the tank use a yardstick to measure the depth. I always checked my tank every two weeks & topped it off to eliminate running low on oil. Never let it get below half full. 

And I almost forgot, since it is a vacuum system, the caps on the oil tanks need to be sealed.  They can crack or have the rubber seal go bad.  My boat had a remote fill that was on the outside of the hull in the rear.  I could always hear the oil gurgle when it reached the bottom of the fill neck. 

Try cleaning the outside of the plastic tank, when they get dirty it becomes very difficult to see thru. Had to do that on my Merc OB.  As hard as I tried, I couldnt see the oil level....cleaned sight glass and tank....now it is very easy to see !!

If you don't have a remote oil fill, un-strap the tape and and lift it up to get a better view. You might try cleaning the outside of the tank to make it easier to see. 

I would just make up a nylon dip stick with a tee handle. They have small square stock at the hardware store. Sort of like metal key stock. Keep in in a storage compartment in the boat so it doesn’t get lost. Easy to wipe down. Try to keep a spare quart of oil on the boat also.