What's wrong with my boat?

[laopi]

Hi,
I had a 90's 40 HP mercury, when I drove on lake today, the reverse and forward with low speed all fine, when I try to speed up, I heard a very load noise from motor, and speed won't change.
Thanks.


peter

[fratri]

I don't know the answer but have a few questions, what kind of loud noise, is it from the engine itself or down in the lower unit? Any chance you can record a short video with sound?

[rick_iles]

Sounds like a spun prop ...

[dean.f]

Sounds like a spun prop ...

Those have that rubber shock absorber in the hub right?

[rick_iles]

Those have that rubber shock absorber in the hub right?

Yes, if the prop has spun, the rubber insert has come loose from the centre hub or the prop itself. It will be fine at low speeds, but will begin to slip with higher torque.
Im assuming the loud noise from the motor, is just the normal engine sound at higher revs.....just a guess !

[trimmer21]

Yes, if the prop has spun, the rubber insert has come loose from the centre hub or the prop itself. It will be fine at low speeds, but will begin to slip with higher torque.
Im assuming the loud noise from the motor, is just the normal engine sound at higher revs.....just a guess !

That's my guess,too. I had a 98 Merc SeaPro that the same thing happened. I hit a boulder on a shoal that spun the sleeve and cracked the prop. A new prop fixed the problem.

[sabmgb]

spun prop would be my guess if the sound is just engine revving, like others have said. I had this happen once, could basically go a little over trolling speed, but if I gave it more power would just rev up.