Question checking oil level in Yamaha outboard

[JiminVA]

I recently purchased a new Yamaha 2.5 hp outboard for my dinghy. It has a sight glass for viewing the engine oil level, but for the life of me I cannot determine what I'm supposed to be seeing through the sight glass to gauge the correct oil level. The user's manual is not helpful to me.

So my question is, if I use the dip stick that is attached to the filler tube cap to measure the oil level, should the dip stick be read after

a) Screwing the cap with the dip stick back in place?
b) Just inserting the cap with the dip stick until it rests on top of the threads?

Method (a) gives a reading that is about 1/2 inch higher than method (b).

I cannot find anything in the users manual about which method gives the right reading.

Thanks for any help.

[a64pilot]

I have not seen anything with a screw in cap that you screwed it in to check oil level, from little Honda motorcycles as a kid, to Honda generators, Yanmar transmissions etc. They are all checked by not screwing in the cap.
Not saying your engine is different, but as bet it’s not.
On motorcycles and turbine engines that have oil level sight glasses, usually half way up is the full level.
Book doesn’t say on either?

[JiminVA]

The engine oil filler tube has a yellow plastic cap that screws into the tube. Integrated into the plastic cap is a short dip stick. Unfortunately the manual is silent as to how to get an accurate reading. I’ll try to get and post a photo.

[a64pilot]

Is this your motor?
If so page 19 and 20 show you how to check oil level
http://www.yamaha-motor.com/assets/s...07-04_1376.pdf

[mvmojo]

If it's a round sight glass, oil level should bisect the middle of the circle, i.e., 1/2 way up.

[Boatyarddog]

Visual check thru the sight glass.
1/2 to 3/4 of the sight glass, In the upright,not tilted position.
Yamaha dealer here.
Cheers,
SV Cloud Duster

[merlinuxo]

Screw it in to check the level.
Page 37
https://cdn.yamaha-motor.eu/owner-ma...BVF819974E.PDF

[JiminVA]

Originally Posted by Boatyarddog

Visual check thru the sight glass.
1/2 to 3/4 of the sight glass, In the upright,not tilted position.
Yamaha dealer here.
Cheers,
SV Cloud Duster

Thank you, this is helpful but I’m still trying to understand why what I see doesn’t match p.20 of the manual, which seems to show some kind of internal tilted disk supposedly visible through the sight glass that indicates the upper and lower oil levels.

I don’t see the disk. Am I supposed to? Maybe I’m misreading the manual.

When I do measure the oil level via the dip stick (using the screw in approach) the oil level is perfect. (Between the upper and lower marks). But it’s really hard to see the oil through the site glass. Maybe because the oil is very new and still very light in color.

[a64pilot]

Originally Posted by merlinuxo

Screw it in to check the level.

Page 37

https://cdn.yamaha-motor.eu/owner-ma...BVF819974E.PDF

It does seem to indicate screw it in to check level.
Interesting to me is the the window on the bigger engines isn’t used to check level, just there to watch the oil splash around?