Propeller Protection

Short answer is - typically not for pleasurecraft. Some commercial gill netters fabricate cage like protection to keep nets from entangling with props. There would be hydrodynamic lift that would occur when operating a "U" shaped bracket below the props, which could have a negative, or even positive effect, but would have to undergo a fair amount of trial/error/fitting to dial in, including multiple haul outs. If you make it too strong, you run the risk of punching the attachment points on the bottom of the hull through the hull bottom, so this may be a no go unless there are clever designs already in practice somewhere.

An electronic alternative - side scanning sonar or orientate the transducer facing forward at the bow to get a forward scanning image to warn of impending obstructions. This is not necessarily a cheap option although and may not be effective at all speeds.

Some reading: http://www.pbo.co.uk/gear/5-forward-looking-sonar-tested-29321

Find a spare prop set on the surplus/used prop market for added piece of mind.

Your best bet is to be extremely careful when your running in shallow water. Know the color of the water. Watch the water depth and know your hull depth.
We all have the same concerns and trust me the 454 props are a lot less than a large yacht where many props run 20-50k.

What kind of electronics do you have on board, especially with regard to depth? What is your draft? Are the areas you're encountering not marked and not on your charts? Is this the first time you've had problems or have you had repeated ones? How fast are you going when you hit?

YES- it's called charts and a chartplotter. Knowing where you're going and avoiding places that are too shallow cures bent props.

Kort nozzles come to mind. There was also some ring props years ago but have not heard any recent news on them.

Years ago (1960s) I had an I/O in partnership with a friend. He ruined at least 2 props a year. I never did. I think it's the captain.

Anything you build around your prop will probably bend and contact the prop, resulting in more damage not less. A friend of mine has an old Chris Craft Commander with a deep keel that was intended to protect the props and rudders, among other functions. Adding more center keel might protect the props, maybe just a skeg, even if it bent it would be fair warning. If it were too sturdy, it could damage the hull instead of bending.

I'm sure their is a website that will tell you at all times what the current depth should be (or correction should be).

The Montreal section of Seaway adjust the levels of the canal but it takes months just to lower one inch.
About twelve years ago Lake Erie was at a very high level and had to be lowered so the Welland Canal increased the water flow around the locks for ten months which did not effect shipping, but in the Montreal section of Seaway they had to stop shipping for ten hours a day for ten months two days a week because of the increased water flow ships could not navigate.
When you see the water level drop one foot over night is because of storm wind blowing the water to the west end of Lake Ontario which will last for one or two days.
As Lake Erie is a shallow lake I have seen marinas in Buffalo with no water as the wind is blowing down the lake. There were many days this past year when ships had to go to anchor in Lake Erie as there was no enough water.
https://www.google.ca/search?q=seic...v&ved=0ahUKEwiH7JyW6qTSAhXh7YMKHXY8CWwQsAQIIA

My boat draws about the same as yours, and I'll not intentionally go into water I think is 5' deep. If your props are a foot off the bottom, they are pulling things off the bottom, like nets and lines and things that can cause problems. A foot-tall obstruction isn't unlikely, an old log or rock or rusty barrel. I don't know what to say about those pesky ten-foot wakes!

Adjust your steering nut, and you will have fewer prop strikes.

1000 islands said: ↑
"My draft is supposed to be 40" according to the manual, but it is all dependent on fuel, & water levels, all the stuff the admiral has brought on board and how many guests she has invited....so I always consider my draft to be 48".."

and then said:
"So when going between 2 islands that had 5' of water last week might only have 4' and I am heavier than usual and a cruiser has just went by pushing a 10' wake and when I go down after the wake BANG!!!! just enough to put a small ding in a prop, but enough to put it off balance."

If I might be so bold to suggest, that if your draft is 48", and there is only 4' of water. . . there is immediately a problem, irrespective of a wake!!

Another issue you should thoroughly acquaint yourself with is the phenomena of "squat" of a vessel, and how it is magnified in shallow water. From what you've described in your operational theater, you will constantly be dealing with it. And while you are discovering the vessel's squat characteristics, take note of how the vessel's maneuverability is impacted by "shallow-water phenomena". Aside from being quite the eye-opener, you most likely will save a bunch on hull damage AND prop damage.

Fair winds and following seas, 1k islands!