Knocking sound at full throttle

[mtbeatle]

Sorry for the duplication, but given the new last paragraph, I thought this topic may be more suitable under this topic.

Hi there,

I have just bought a boat and tried it out for the first time today.

It is a Pioner Maxi with a 15HP 4 stroke Yamaha outboard. It is about 7 years old.

There were four of us in it to start with and it seemed to work perfectly from slow to full power.

I then went out in it myself so it was obviously a lot faster (about twice the speed) and when I got up to full speed something made a 'knock knock knock...............' noise.

Im not sure its the outboard itself but was certainly coming from the rear of the boat/engine/propeller area.

Any ideas? Is this something to worry about?


It has been suggested that because my propeller has a few chips on it and one of them fairly big, that this could be the cause. Any thoughts?


Thanks

Craig

 

[Silvertip]

Re: Knocking sound at full throttle

Not likely the prop unless the prop is loose. You have a four stroke engine. Did you check the engine oil before you went out. This engine is just like the one in your car. Unlike a two stroke, It has a crankcase than holds the oil. If oil level is not up to the full mark on the dipstick, you need to add oil. Running it out of oil is death to the motor as it loses lubrication. It also gets very expensive.