Boat "rumbles" in reverse...normal?

J

JeffR

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Hello all...I while back I posted some questions regarding diesel engines, and since then, we've purchased the boat and love it. Thanks again for all the input!

This is my first boat with inboards and diesels (only relative to my question because of higher torque, bigger props, etc) and I have what might be a strange question.

I know props are not made for reverse, are not efficient, and will make noises, etc when in reverse. However, this boat seems more extreme than what I'd ever expect. When I back the boat into the slip, for example, I don't notice any extreme or abnormal noises. But, if I have any forward motion - I'm talking very slow as in forward motion in marina - and I have to put the boat in reverse as you would to slow or stop to allow a boat passing, it makes a heck of a racket and rumble, almost a knocking sound as if I hit something, until it gets settled and then it quiets to "normal".

Do I have problems, or should I be concerned, or is this typical of the larger props, higher torque, etc?

Thanks.
 
Likely your rudder/rudders fluttering. Not really a problem. To check get the boat in an open space with room to go in reverse, put it in reverse and turn the wheel see if the noise changes likely will, maybe even stop.
 
Mine doesn't do that I'm not sure what that is but rudders sound possible.
 
Check your rudder zinc's also. If one is loose it will sound just like that.
 
Sounds like Cutlass bearings. I guess it could be several things, motor mounts, gear to shaft coupler misalignment or something loose, gear plate pressure, but first check for a rumble in reverse is a cutlass bearing.
 
There are several possibilities but check the "free stuff" first... ;)
 
Lots of props cavitate when heavily loaded. If it "quiets to normal" I wouldn't worry about it, but if it rumbles ALL the time I'd be concerned, check the cutless bearing.
 
Of course, check the free stuff first but it's probably one or more of the items Silver Lining mentions above. It's not uncommon for lots of boats to rumble in reverse. Just that a boat with good alignment, and good cutlass bearings shouldn't do it. A little rumble may be negligible without consequence but over time I have seen even the transmissions and their bearings affected. Your mileage will vary. I have seen some neglected for years, others not so lucky. If your packing often needs adjustment, it's a good bet your alignment is out.
 
Massive cavitation. As you noticed, this happens when you reverse while still inforward motion. Normal noise.
 
Maybe one of your paddle wheels has a stick in it.

But seriously maybe you should try double clutching between shifts.

Really though, all kidding aside, whats your transmission? What brand? Is it a typical Velvet Drive?

Velvet drives will sometimes give off a sound in reverse especially at idle speeds. Something to do with the planetary gears or something like that. It's normal and goes away when more rpm is applied.
 
Jeff, if this is used boat ask the old owner if this is normal, as others have stated on some boats it is.
 
Thanks for all the replies. I'll definitely check the items suggested, but I'm leaning toward just cavitation (hopefully), and not being used to the larger props and higher torque.
 
When the New York Waterways ferryboats which cross the Hudson River leave the slip and turn (they are not double ended) they have one engine in reverse and sound like they're coming apart.
 
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