New Mercury prop spun for no aparant reason?

W

wijames

Cadet
Joined
Oct 20, 2010
Messages
12
I have a new 40 HP 4 stroke Mercury bigfoot engine on a 18" Tracker Baby Bass Buggy and was out this weekend 6 miles out in the gulf on a calm day and on the way back at just under full throttle the prop spun. I immediately tilted the motor to see if I had caught a crab trap or wrapped something but the prop was clean. I was able to limp back in at 1/4 throttle and when I got in pulled the prop. There was nothing wrapped behind the prop and no damage to the prop at all. Could it be that the prop is not strong enough for the weight of a pontoon boat in the gulf? Any other ideas or thoughts?
 
Texasmark

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,557
Re: New Mercury prop spun for no aparant reason?

If I have my facts right, the lower unit on the bigfoot is the same 4 1/2" (I think) dia. lower unit used on the mid range engines like my 3 cyl 90 hp. Unless there is a prior use, or mfging. problem, I assure you that that prop should be able to handle your 40 hp. The gear ratio is 2.33 and the prop would be shallow pitched to accommodate the 40 hp. Probably in the 12" category. I run a 24P at 5800 engine rpm's on that lower unit/13+" prop dia....many thousands of them on the water.

HTH,

Mark
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: New Mercury prop spun for no aparant reason?

The FloTorque hub wasn't tightened down tight enough to force the hub into the prop. They feel tight on the shaft, but when run, they get loose and it beats the plastic hub to death.
All you should need is a new plastic hub.
 
W

wijames

Cadet
Joined
Oct 20, 2010
Messages
12
Re: New Mercury prop spun for no aparant reason?

I looked at a picture of the FloTorque hub and it doesn't look like I have one. My set=up doesn't look like that at all.
 
Texasmark

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,557
Re: New Mercury prop spun for no aparant reason?

How about a picture of your prop!
 
R

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Re: New Mercury prop spun for no aparant reason?

Since it's new and you apparently haven't hit anything, maybe take the prop back to the dealer for a no charge replacement...they've usually got some extra props around. Good Luck!
 
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