Mercury 40 Four Stroke BigFoot Noise

[haggertb]

I have a new Mercury 40 Hp Four Stroke BigFoot on a pontoon boat. The motor is close to brand new, has maybe 5 hours on it. It seems to run ok, but there is this "rubber on steel" noise that changes pitch slightly as the rpm's go up, and gets louder as the rpm's go up. I thought these motors were supposed to be really quiet, but the whine is louder than the exhaust noise. My imagination makes me think it might be the water impeller. How easy would it be to take the lower unit off while the boat is in the water? Or is that a bad idea?? The noise is present at idle, but very faint at idle. The tell-tale stream is very strong at all times.<br /><br />Thanks,<br /> Bill

 

[Bear]

Re: Mercury 40 Four Stroke BigFoot Noise

Check the drivebelt tension. Maybe it is to tight.<br /><br />/Bear

 

[trevorcday]

Re: Mercury 40 Four Stroke BigFoot Noise

These motors are normally very quiet. They do have a funny little whistling sound that they make at about 3000 rpm but it goes away as the rev's climb. If the sound you are hearing is always present this is not what I am trying to describe.

 

[wilde1j]

Re: Mercury 40 Four Stroke BigFoot Noise

Bill, sounds like the motor is still in warranty. I'd be reluctant to start taking stuff apart, when the selling dealer should be messing with it, especially if it turns out to be a warranty issue.

 

[wayne c.]

Re: Mercury 40 Four Stroke BigFoot Noise

Bill, I had what I think is a similar problem w/my '02 90 hp Merc 4-stroke. It was what I call a Harmonic Whine. Does your engine have what Merc calls a FLO-TORQ II Prop ? This prop has a separate plastic hub. If so try a standard prop with rubber hub. When I did this, noise stopped! Got this advice from another on this board. Told dealer about this, he said Merc knew about problem, but wouldn't admit to it. I know it sounds funny, but it took care of problem, let us know what you come up with--Good Luck !

 

[haggertb]

Re: Mercury 40 Four Stroke BigFoot Noise

Thanks for the information from everybody. The FLO TORQ II answer seems to match my symptom best, as I do have the FLO TORQ II prop. I will have to see if I can get a different prop and try that out.