Motor revved up and the boat slowed down!

[chap]

Hi,<br />I was cruising around a lake at full throttle with a 9.9 hp (1995) Mercury outboard motor. The motor suddenly whined and revved up well beyond what is normal at full throttle and the boat slowed down. <br /><br />I checked the prop, it was turning and appeared okay, so I gave it more throttle. Bubbles and smoke came out of the exhaust and there was hardly any forward motion. I shut off the motor and restarted it with no problem and it idled perfectly. I was able to "limp" back to the dock at a very low speed. <br /><br />Out of the water, the prop appeared normal to me, but I'm no mechanic. Any thoughts on what might have happened? <br /><br />John

 

[ZmOz]

Re: Motor revved up and the boat slowed down!

Sounds like there might be a problem with the prop hub. Take the prop off and inspect it carefully.

 

[Barnacle_Bill]

Re: Motor revved up and the boat slowed down!

ZmOz is correct, the prop needs to be re-hubed. That is a small prop, so it might be economically feasible just to buy a new one. (unless its stainless).

 

[d67bart]

Re: Motor revved up and the boat slowed down!

Don't feel bad I gwas on vacation two weeks ago ,coming back from a bad day on the lake catching nothing but drowned worm's, half way across the two mile lake the rpm went way up and the boat slowed down .Limped back at just above idle and found spun hub in stanless. With my motor in gear I was able to turn the prop on it's shaft . I've got a 40 hp mariner , I think your 9.9 may have a shear pin.