Kicker bracket position

[Hyperion]

I recently bought a 24' sailboat for my fiancee, and it came with a LS Mercury 9.9 on the kicker (I've read all the opinion regarding Merc outboards... it came with it. Let's leave it at that). The kicker bracket is mounted on the median of the centreline and port side of the stern (i.e. on the stern halfway between the rudder and the port side). When under power, the thrust sits the stern down a little lower in the water, putting the water line about 3 or 4 inches above the anti-cavitation plate. While we don't intend on sailing this small boat in weather, 3" of clearance often means that even a small swell will lift the stern and consequently the lower unit of the outboard out of the water. This wreaks havoc on the impeller, not to mention the boat's forward motion.

I have two questions. First, at what depth should the anti-cavitation plate of an outboard on a kicker be submerged to reasonably alleviate this issue?
Second, is it feasible to remove the kicker bracket from its existing location, fibreglass in the old holes, and remount it an inch or two lower? Would there be considerable structural issues?

Thanks for any constructive help you may have.

[CharlieCobra]

It depends on how far above the water the bottom of the mounting plate is. If it's in the water while underway, ya need to get a long shaft motor. What you describe is what I deal with because I have a medium shaft motor but for $125, I just couldn't pass it up.

[knotaloud]

Have you thought about an adjustable bracket, or a bracket with more adjustment? Garelick makes one that has 15" of vertical travel; you might be able to just lower the engine a few notches when the waves kick up. Garelick Aluminum Auxiliary Motor Bracket for 4-Stroke Motors - Hopkins-Carter.com

[Faster]

It may be possible to relocate the bracket lower down - check the reinforcement available or add strong backing plates if they are not already there.

The reality, however, is that stern mounted outboards will occasionally be lifted free and cavitate, naturally at the most inopportune times.

Your need to transit first Narrows with this boat will mean the such episodes could be more frequent than you'd like. Again, check the current tables.

3 -4 inches of submersion sounds about right - some boats "squat" so much under power that the nearly put the powerhead into the water, so watch for that. Also a lower mount makes the motor slightly more vulnerable to following seas, and makes it more difficult to lift, tilt, throttle and steer from the cockpit.

[Hyperion]

Charlie - yeah, I've got a long-shaft. The mounting plate is well above water while underway. Couldn't say exactly how high, but at the lowest adjustment point, the bracket is still well in the dry.

Thanks for the link knotaloud. I'll check it out, but was hoping for information on repositioning the existing bracket - if it's feasible. The boat isn't great and I don't want to sink much more into it. I'd like to sell it once she learns to sail, and just let her sail mine after that.

[Hyperion]

Faster - didn't see your post while I was replying. LOL Your knowledge of my requirements is exactly the issue. It was primarily during that episode in the Narrows that caused me the concern over the position of the kicker.

I was thinking a steel backing plate would probably do the trick. I think with 1.5" of additional submersion I'll be in pretty good shape.

[knotaloud]

I suppose it depends on your bracket, but rather than drill more holes in your transom, it might be possible to fabricate something that would allow you to lower the mounting pad an inch or two. Not where the bracket attaches to the boat, but where the actual mounting pad bolts to the bracket. I'm think just a flat 5/16" or 3/8" thick piece of square aluminum with offset holes. Either that or drill new holes in the pad and lower it on the bracket, or....maybe just cut an inch or two off the top of the pad so the engine sits a little lower. Okay, I'm done.

[Hyperion]

Knotaloud - actually, prior to considering putting more holes in the transom, that is exactly what I was considering. My only worry was that perhaps in adding a new mount which was offset, I might be inadvertently screwing up the structural integrity of the bracket, especially under thrust.

I work for a tire manufacturer, and see first-hand the significant impact that a 5mm adjustment to wheel offset or a 0.5% adjustment to camber can make. It seems minor until something fails.

I'm probably being overly-cautious in this case, though. Thanks for the input; I may well be going this direction.

[Faster]

Originally Posted by Hyperion

I was thinking a steel backing plate would probably do the trick. I think with 1.5" of additional submersion I'll be in pretty good shape.

Use Stainless or Aluminum instead of steel.. or a composite of some sort.

[sailingdog]

Even marine plywood, properly coated in epoxy, is a far better choice for a backing plate than plain steel would be.