my tracker 25hp 2 stroke is making some weird noises. im not sure if theres something wrong but the motor seems to run strong. when i run the motor and its hot it starts to make a sorta rattling noise coming from the motor. hard to explain almost sounds like something rattling around inside as its running. doesn't do it when it first starts just after its had a run.  otherwise it runs great. just have to touch the key and it fires right up and it pushes the boat 25mph. any clues? places to start? or is this just a common noise for 2 stroke outboards? im wondering if its old gas maybe, sounds almost like detonation on a car engine, maybe the timings to advanced and it is detonating? would explain why it makes the noise after the cylinders are hot.

If your sure it's internal, you have a problem, 2strokes don't rattle.  Most mercs run a ratcheting prop drive so the prop free spins when you let off the gas, preventing the decel knock common with many other motors.

Might pay you to have it checked out.  There are numbers of things that can cause wierd rattles.  Bad wrist pins, cracked piston, a bad main bearing, exhaust tuner loose or broken off or even a lower unit can make it sound like the motor is making the noise.  Just make sure you check everything before thinking about going into the power head.  I just had a friend that just took his 150 merc power head and put on a remain'd one because it had a serious sounding rattle in it.  Still had the rattle after swapping powerheads, his exhaust tuner had boken loose and rattleing around in the mid section.

try some dry gas to your fuel,and check the mix,has it been setting a while,does it pee out the back as it used to befor this started,also is your engine with or without oil tank?also recommend some stabil to your fuel,good luck and good fishing,i have a 150hp 2 stroke,it made this rattle,and it was the oil type i was useing,tryed to be cheap,now i buy only the good stuff thats recommended,luckey me,once i emptyed my oil tank an switch engine was fine,water really adds up in plastic tanks,condensation as the temp changes,so do the basics first,befor you shop it,could save you some money,then after you have,if problem still exist you can put in the shop;hope this helps

Check your lower unit oil if it runs fine at idle and noise increases with speed. I swore it was motor but just the lower unit. Had a no it all mehcanic put the lower magnet screw in the top hole.

Garnet