2014 mercury 90hp 4 stroke overspeed

[MwrEngineRepair]

This problem started out of no where. The engine does fine at low speeds but once I bring the rpms above 2500 it surges and goes to 5000-6000. It produces a weird revving and turns the craft to the right hard. The throttle cables are fine and lubed up, not sticking and no excess tension. I really need some ideas on what’s happening. All I can research is the overspeed alarm and nothing about actual overspeed.

 

[RickM46]

Is that Merc EFI?

 

[MwrEngineRepair]

Is that Merc EFI?

Its a ME 90L 4s

 

[fastjeff]

Slipping prop hub?

Jeff

 

[RickM46]

What Jeff said; when I asked if it is EFI, I meant is it fuel injected or does it have carbs? I am not familiar with fuel injection but I have read where there is a low speed black box and a high speed black box. Nonetheless, per Jeff, have you tried a different prop?

 

[MwrEngineRepair]

What Jeff said; when I asked if it is EFI, I meant is it fuel injected or does it have carbs? I am not familiar with fuel injection but I have read where there is a low speed black box and a high speed black box. Nonetheless, per Jeff, have you tried a different prop?

Sorry, it is fuel injected. I will try changing the prop out in the morning, the problem is still there even when using throttle only. I will also look into a high speed black box

 

[RickM46]

I am no expert on EFI and will defer to others on the forum; I saw on some other EFI problem threads that there is some electronic component that controls low speed/idle and another that controls high speed.

 

[MwrEngineRepair]

I changed out my iac valve and there have been no problems since

 

[RickM46]

Nothing like success! Idle Air Control valve.

 

[tinchotri]

Hi Did you solve the issue? I have a mercruiser 5.0 mpi, everything works well below 4200 rpm, above 4200 rpm the overspeed alarm went on. thanks Martin