bump in reverse

[ab1]

I am hoping this is not a problem, but rather a normal occurence...

When I launch my boat (93 150 Johnson FS) and shift into reverse, I get a very dull thud from my outboard...usually just one or two thuds a couple of seconds apart. It is not hitting anything and only seems to do this in the very shallow concrete bottomed launch area. I can reverse with no problem in deeper water. I was thinking the prop wash in reverse is pushing against the concrete and just slightly bumping/pushing the motor up. Is this normal?

I've had other boats and never noticed this, but they were not outboards.

Aaron.

 

[ab1]

Re: bump in reverse

Had it back out and still doing this...any help you can offer would be great. It's a bass boat and when I launch and shift to reverse I get a couple of bumps almost like I am hitting bottom, but I am not. Is this a cable needing adjusting, or the prop thrust pushing the outboard up a little bit. The bump is pretty subtle, but definitely there.