Mercury optimax 300Hp 2 stroke issue
Had an issue with my mercury optimax 2 stroke 300 HP engine and wanted to run it by you guys before I take it to mechanic. Just recently bought a boat and The only mechanic I’ve had so far seems to have figured out I don’t know anything about boats and has been overcharging.
When I accelerate my boat with a mercury optimax 300HP two stroke initially it works fine. After a minute or so if I am going at a fast speed the RPM seems to jump and I can no longer accelerate further. At times the engine will also slow down without me moving the throttle. It didn’t used to happen when I first bought boat and it doesn’t happen all the time. I know boats don’t have gears but it feels as if it is stuck between two gears in a car and bouncing between both.
I tried adding a video to show the sound it makes and the RPM jumping but it doesn’t allow me to add videos.
The RPM jumps from 3 to 3.5 and back to 3 and will make like a pulsating noise.
This does not happen if I am going at a very slow speed <8 knots. Only when I start to pick up speed it’ll suddenly get stuck and not accelerate further. When I first bought boat there was no issue with me hitting 20+ knots and this did not happen. It started happening rarely and now it happens almost every time.
I read online it can be a gas/air filter, the engine not getting enough gas or something with an alternator.
Any guesses?