It may be your starting technique.
1. Lower motor so that it is at or close to the normal running position. Be aware of the water depth so you don't damage the prop when you engage the gear case.
2. Prime the motor by squeezing the rubber primer bulb 4 or 5 times until it becomes firm. If it does not get firm, then you may have a bad or leaking needle valve in the carburetor(s).
3. Advance your throttle handle forward in the "Neutral Fast Idle" position. To place your throttle into the "Neutral Fast Idle" position, pull the throttle handle out towards the center of the boat and push the throttle handle forward. You may have a button on the throttle handle right at the pivot point of the handle that you have to push to release it. The handle will move out about a quarter of an inch. By pulling the throttle handle out, it disengages the gear case and the propeller won't turn.
4. As you turn the ignition key, press the key inwards to engage the choke. Do not engage the choke for more than 3 or 4 seconds at a time, otherwise you may flood the motor. Very easy to flood the motor and really make it difficult to start. You can continue to keep the key turned to the start position without pushing in to engage the choke until the motor starts.
Once the motor starts, give it a short warm up then return the throttle handle back to the neutral position, and it will pop back in. Now the gear case is engaged so that when you move the throttle handle forwards or backwards, the propeller will turn.