Motor goes full throttle while in idle

[TCummings]

I start my boat from cold start and put it in idle. After a minute it will rev up to full throttle without doing anything. I try and turn the engine off and it doesn't respond. I end up having to disconnect the fuel line until it dies. I am not sure where to start on this one. With the engine not turning off when turning the key off is probably a faulty switch but the reving to full throttle I am not sure on. Any suggestions would be appreciated.

 

[pinecrestwoods]

Re: Motor goes full throttle while in idle

Wow.



What boat/motor is this?

 

[TCummings]

Re: Motor goes full throttle while in idle

Sorry, it is a 2001 Mercury 50 HP. The boat model is a 2001 Sea Fox 16ft center console. I bought it from my uncle. It had 10 hours on it over a 9 year period.

 

[Dave1027]

Re: Motor goes full throttle while in idle

Either the throttle is stuck open or the timing advance is not set correctly. Something may have come loose. A "sync and link" is in order.

 

[Superjetjim]

Re: Motor goes full throttle while in idle

Sounds like an airleak to me, it causes the spark plug end to get so hot it deisels (needs no spark to continue running) it shouldnt do it in the water, just on the hose - is this what your seeing?