Mirage Drive Hull Thump

Hi, I bought a Mirage Revolution this winter and can't wait for warmer temperatures to get on the water. Meanwhile, I put the drive in the boat to try it out. Well, I heard a giant thumping sound coming from the hull when I moved the peddles. I noticed that one of the flippers was striking the bottom of the boat while the other was about a half an inch away from the hull. The drive also looked askew: when I had the flippers lined up vertically underneath they were slanted to the starboard side, the same side as the thump. I re-installed the drive a number of times with the same result. I then put the drive in backwards and the flipper now thumped the port side. So, I took the time to examine the drive out of the boat and it sure looks like the flippers are not properly aligned.

When the rear flipper is aligned on the vertical axis the front flipper is leaning starboard; when the front flipper is aligned on the vertical axis the rear flipper is leaning starboard. In each case the pedal shafts are slightly out of alignment.

When I properly align the pedal shafts the flippers line up with each other but they are not on the vertical axis but are now both leaning to the starboard.

This faulty alignment is what is causing the thumping on the hull. The sound is quite loud....I've heard it on some YouTube videos, too. Not only will it be annoying on the water it will spook the birds I hope to photograph. Is there anything that can be done or is an exchange required?

In what may be related, one of the pedal arms is loose no matter which adjustment hole it is set in. If I hold everything on the drive steady and push the starboard pedal arm it moves with a noisy jerk. The port pedal arm does not move in this manner and is also much stiffer to adjust. What is going on there and can I fix it?

I'm looking forward to going out on the water with my new boat but have concerns about both of these issues. Thanks...a Maine Guide

Sounds like simple chain adjustments to align the fins.

This is not difficult, but your dealer should handle this for you under warranty.

If you want to do this yourself... Look at the owners manual. It explains some of the adjustment, but roadrunner and others here in the forums have written much about maintenence and adjustments.

Also refer to the FAQ at the top of this forum: http://www.hobiecat.com/community/viewforum.php?f=21

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Loverid, welcome to the forum and congratulations on your new boat! The pedals rarely come perfectly aligned from the factory. It's an easy process to fine tune them though, especially with the '08 or newer Drives. While you're at it, check your cable tension and make any adjustments as you align the fins.

With some of the hull shapes (like the Revolution and Adventure) it is possible to smack the hull bottoms with the fins. When you get your boat in the water, you should set the pedal positions so that the pedals do not normally thump against the hull with your legs extended (without hyper-extending); a slight fin misalignment would not normally be noticed operationally. If someone is experiencing noise from the Drive, it is most likely due to the pedals being adjusted too close.

There is a variable amount of slop in the crank arms where the pedal adjustment pin goes through. Again, when you're pedaling, this should not end up as an issue as your leg will keep the pin pressed against one side as you pedal. If it is bothering you, show it to your dealer and ask his opinion.