no
99% of the outboard motors need 50:1
No.
The 15 horsepower Mercury outboard motor does not have a water pump. The outboard motor is air cooled and does not have a need for circulating water.
50:1 you can use any two stroke oil. You don't need to buy the expensive stuff, as they all burn the same.
do you need a boat licence for a 5hp outboard
Gas and oil are mixed on a two-stroke engine, but you don't always have to do it. Some two-stroke outboards have oil tanks and mixing systems that dispense the correct amount of oil for any operating condition; if you have this, you need to check the oil tank every time you add fuel.
A engine exchange will be necessary. Remove the diesel and install a gasoline type.
how do u remove the lower uint on an outboard motor? Depends on the outboard. Some Johnson/Evinrudes required that the powerhead (engine) be removed first for example. Look for a service manual for your particular motor on ebay, and it will tell you all you need to know to avoid problems.
If it is a 2 stroke then use any brand of 2 stroke oil mixed to the correct ratio with gasoline.
100 aph
You need model number to determine model year.
try oldmercs.com you should be able to find a manual there