Mirage clunk on new Revo

I have a new Revolution. Under moderately heavy load, I get a clunk noise near the middle of the stroke. Switched to ST turbo fins, and it's easier to make it happen. I'm no gorilla, but I worry that I may be stressing something.

I've got the locking cams tight, and I've checked the cable tensions (they were VERY loose when new, and one was pretty loose again after a couple of days on the water).

It isn't anywhere near as severe as a skipped tooth - seems more like the rocking problem posted elsewhere. I can't recreate it on dry land, though maybe I could tether it in a swimming pool.

Any idea what I should check next?

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2x Revo
17' Grumman Ultralight

Hi Ya Rx-7
Just a hunch but I would try moving the pedal crank arms forward
(closer toward the bow) one or two notch holes then pedal at your normal pace and see if that solves it. Often times everything is fine its just that you may be bottoming out the pedal stroke. S-t-r-e-t-c-h out those legs a little bit, move the crank arms forward and see if that helps. Again just a hunch but worth a try. I have found the mirage drives to be very sturdy and reliable.
Cheers
Kepnutz

Thanks for the reply.

This clunk happens in the middle of the stroke, not at the ends. I've very nearly mastered the stroke length thing, so I rarely slap the bottom of the hull, and that noise is quite different in any event. This noise happens on;y under load. I'm an out-of-shape cyclist in my fifties, so I don't think I'm exceeding reasonable pressure on the mechanism.

Sturdy and reliable is good, but strange noises under stress are disconcerting. If there's something wrong, I want to adjust, fix, or compensate. It feels like I'm abusing it.

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2x Revo
17' Grumman Ultralight

Ok..
How bout something stuck in the chain link,like a small rock or shell.
Ive had that crunchy noise thing happen too after beaching every now and then.
Maybe the shop you bought it from or a friend with a hobie mirage drive will let you swap out your drive for another mirage drive to run a test and see if its different than yours.
The other thing I can think of is perhaps the cables might be tooo tight or the sprocket is bad. A sprocket is only ten dollars and takes ten minutes to change out. I ran my drives for two years before ever tightening a cable with no ill effect, they seemed to do ok on the loose side. If all else fails its a new boat so I would take it in to the shop for warranty repair. Hobie always covers any warranty problems with their new products
Kepnutz

Now that I have turbofins on mine, I could try and see if I get the same noise with my wife's. Before this, I couldn't tell them apart. I could also try my drive in her hull (stop it, folks - this is a clean forum!)

A friend is so taken with these that I'm going back to the dealer with him to look at one for him It's a long drive but since I'm going anyway I can bring my drive there and see if I can make noises in one of their hulls.

Seems like the noise is not normal and healthy behavior - that's really what I needed to know.

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2x Revo
17' Grumman Ultralight

There is a possibility this is not the Drive per se, but the interaction between the Drive and the Drivewell. Take a close look at the rear outhaul block on your Drive and see if there is any chaffing as appears in this picture:


If so, you would notice a little clunk as the fin rotates near the middle of the stroke, and the wide portion of the outhaul block makes sudden contact with the Drive.

Thought it was chain jump, but I was wrong. Still undiagnosed. More tests underway. Outhaul block is not hitting anything. Feels like what I'd expect chain jump to feel like, though not as severe.

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2x Revo
17' Grumman Ultralight

Sounds like the drive is just rocking a bit in the well. Even with the cams tight, there can be a little gap in the front or back that allows the drive to rock back and forth just slightly and produce a light knocking sound. You hear it early to mid stroke as you shift force from one pedal to the other. Try taking a small piece of duct tape, and putting it on the little shelf in the front of the drive well. Then put your drive in and try it out. See if that gets rid of the knocking sound.

I also am expieriencing the clunking noise on the mirage turbo fin drive. It never did it on the regular fins. My clunking happens at the begining of the stroke. I don't understand where to put he duct tape. Has this worked for anyone else? Does anyone know why this is happening?

A little more data: I'm pretty well convince that the noise comes from the drive moving back and forth by the right hand locking cam. The pocket in the hull and the rod on the drive both show a little wear on that side. I've been really tightening down the cam lock, but I think that the pocket is a little elongated front-to-back. If I can figure out something to wedge in there I'll see if that quiets it down.

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2x Revo
17' Grumman Ultralight

I found my problem. The cable slipped off the pulley and around drive. Replaced and tightened it securely and fixed my problem. Hope you fix yours.

The clunking noise you have described (occurs at mid stroke, worse under "heavy" pedalling) is the same as I have experienced on my drive in my Oasis. Mine would usually happen around 5 mph in that hull. Both drives I have do it. On several occasions I have had the chain jump a sprocket so I assumed it was related to that. I've got an older drive and boat (2003 ish) with the ss sprockets. Since it never happened at my cruising speeds, I didn't worry about it too much, I just avoided sprints or rabbit starts. It did always bugged me though. I've read RoadRunner's cable tightening recommendations and will see what happens next time out. Unfortunately, my wife and I have moved from Cali to Houston area and this area sucks for kayaking compared to Cali so it may be a while. However, the midwest is in our future, as is an Adventure, and I can't wait for that!

I was on Navaho Lake (north central New Mexico) last Friday and played with the chain adjustments trying to get rid of my clunk.  Not very successful.  I got rid of it on my wifes (we both use Turbo fins on our Sports) but mine still does it IF I do full strokes and at least moderate pressure.

Could it be that the right stroke speed can cause this?  I cannot feel it in the drive unit-to-boat interface (camlocks), and it doesn't change if I put sideways pressure on the pedals while maintaining the same cadence.

If I go pretty slow, or pretty quick, it doesn't happen.  It also doesn't happen when short stroking for best speed.I suspect it is a cable/chain walking condition, but I haven't been able to get to the magic adjustment that cures it.  I'm wondering if the front fin sweeping past the rear fin is changing the load dynamics where the chain load is shifting. 

I was OK until I replaced the bushings (and will replace the shafts soon because they are badly pitted from salt water corrosion).  Perhaps the angles (with worn bushings) created a wear pattern I have to work through?  Wow....pretty baffling and sure wrecks my confidence in my diagnostic skills!

Regards, JimL

P.S.  Navaho Lake is a pretty incredible (huge) place....but the rangers force you to wear a life jacket regardless of age or sobriety.  Camping and kayaking is best at the south end of the lake, nice rock cliffs to cruise along, small coves to dip into with BIG rocks underwater to tag your drives.  The campgrounds have nice showers (no extra money) and your camping fee also covers your day use fee (unlike the Colorado end of the lake where they charge extra for everything and have exposed campsites with no shade).  No mosquitos, either....unlike Ridgeway Reservoir where we got eaten alive....but that's another story for another time.

Still trying to figure this out. My wife's drive in my hull does not have this problem, but then she only has the standard fins so it's hard to exert sustained pressure for long.

Shimming the axle pocket made no difference.

It's very consistent and starts at the level of effort required at about 5.0 - 5.5mph.

I have a 2008 model drive. The clunk is near the middle of the stroke. I've gone over all the tensions and inspected everything carefully - all good as far as I can see.

I still wonder if the axle is rotating (around a vertical axis) in the hull pockets.

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2x Revo
17' Grumman Ultralight

You can score your drum shaft at the top to see if it rotates, but I believe all current shafts are splined. Even so, I doubt this would be a factor in any noise or performance issue. It certainly wouldn't hurt to check though.