2014 4 stroke 90 RPM fade

[crocksa]

My 90hp has started losing RPM at speed. I can ramp it up to around 4800 rpm, and it will slowly (within 60 seconds or) slow down to around 3000 RPM without the control lever moving. It does not run rough, or miss. It's a slow, smooth deceleration. Any ideas?

 

[510freak]

I'm new to boating as well so take my advice as a grain of salt I'm learning marine as I just got my first boat and working out the issues as I type this. I do have a a background in automotive and motorcycles though I do know the basics. Have you checked if you're getting proper fuel to your carbs? Is your primer bulb collapsing? Suggesting a fuel
Blockage inthe line. Or weak fuel pump? Check the fuel pressure? Clogged fuel filter.

But if it's not backfiring if could be a rich issue being you float valves are bad letting to much fuel in the bowls causing it to run rich bogging down the motor

 

[SoCalBoatGuy]

Could also be creating a vacuum in the fuel tank. Try running it with the cap loosened.