10w30 or 25w40 in 1999 Mercury 25hp bigfoot?

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Gtornai1

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Cant figuer out what oil to use in my 1999 25 hp Bigfoot? Any suggestions? Thanks guys!
 
Barefoot_Johnny said:
this should be an indicator that you need to purchase a shop manual.
Then, you can keep up with maintenance and periodic adjustments.
That is way too nice of a motor to wreck it over something simple.

I am an OMC fan. So don't know too much about Mercs.
Never heard of a manual..... I know I baught one just would rather change my oil before I take it out this weekend while I am waiting for the manual to get here Ino it is either 10w30 or 25w40 just don't wanna put the wrong one in
 
There should be a sticker under the cowling that looks like it has a thermometer on the sticker. This will indicate what weight of oil is acceptable to use in your motor based on the temperature range the OB will be operated in. If no electric start, the 25w40 will make it a bit more difficult to start in cooler/cold temps (harder to pull due to thicker oil).
 
TNtroller said:
There should be a sticker under the cowling that looks like it has a thermometer on the sticker. This will indicate what weight of oil is acceptable to use in your motor based on the temperature range the OB will be operated in. If no electric start, the 25w40 will make it a bit more difficult to start in cooler/cold temps (harder to pull due to thicker oil).
Yea I noticed that sticker after I posted this yesterday.... Went with 10w30 just because it said it was good for all temps.... Thanks man
 

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