oil for motors

I have a 50 hp yamaha engine.  Is it necessary to use only there oil for the motor.

Thank you

I have a 2 stroke Johnson that is 25 years old. Have used different oil brands without issue. As far as plugs, I do those every other year. I will take them out in the year that I don't change them and clean them up a bit. Again, no issues.

I just got my 1st 4 stoke outboard. A 5 horse Merc. It only uses 10 oz. so 3 changes to a qt. that is only `10 bucks. I kow one thing, I dont have to change it very often. It came out pretty clear after 50 hrs. .   I am still so cheap that I am going to look at Fleet Farm & Walmart and when I find it for even cheaper , I will buy some.  As for spark plugs, how often you guys change them? I have a1997  25 horse Merc.  I dont think I have changed those plugs 5 times. I have 94 hrs on my 5 horse . I bought an hour meter as soon as it was new. I wonder if I should change the plug for a whole  $2.57. It trolls for hours  without a hickup , but it seems to start hard sometimes  if I dont run it for 1/2 hr. or so. Needs choke.

Found the owner/s manual for correct oil for a Yamaha 4 stroke motor.  yamaha lube-4-m FC -W or 4stroke outboard motor oil. Thanks for the time and information.

Will be using the QuickSilver Marine lubricant, 4-stroke marine engine oil with a SAE 10W-30                                  '

Thanks for the informaton.  I have a 4 stroke Yamaha.    

I am assuming you have a two stroke that either requires you to mix the oil and gas or the motor has oil injection. If that is the case you should be able to use any name brand oil that meets or exceeds your motors requirements. I would shy away from off brand economy oils as they may not meet your motors requirements. Oil isn’t a place to try and save a buck, just like running ethanol fuel in your outboard to save a few dollars 

Absolutely not required to use Yamaha brand oil. Call any marine mechanic, anywhere....ask the same question. Personally, I use Mercury Quicksilver brand oil - I buy it by the case when it's on sale at Menards.  Never had any issues, no matter what brand of engine.