Full ballast & stopped engine: hydro lock concerns?

[anmut]

I've been following some posts on a Centurion tow boat page on Facebook. Apparently with those boats there's a concern with weighing down the boat with full ballast and stopping the engine for an extended length of time. There are owners of these boats (Centurion being the only brand I'm aware of) that can testify that, when at full ballast and the engine off for a significant period of time (and because motor is sitting much further under the waterline) that they've experienced water creeping back up the exhaust and hydro locking their motors.

I've never read anything like that on this forum - however I wanted to toss it out there see what y'all thought. Personally, I don't weigh my boat down with more than 2k lbs of ballast, (unlike a Centurion where they might have 5-6k lbs), but if that rear platform is underwater, it would move the water table higher as it relates to the exhaust box and everything further down the line.

Thoughts?

 

[Julian]

Interesting thought.....never heard of it happening....but doesn't mean it couldn't. We have a lot of people surfing behind these boats....and everyone is shutting down their engines between riders/sets (because otherwise they'll be unwrapping ropes from their shafts all the time!!!). I wonder if the water boxes have backflow baffles of some sort??

 

[anmut]

Interesting thought.....never heard of it happening....but doesn't mean it couldn't. We have a lot of people surfing behind these boats....and everyone is shutting down their engines between riders/sets (because otherwise they'll be unwrapping ropes from their shafts all the time!!!). I wonder if the water boxes have backflow baffles of some sort??

That’s what I was thinking. According to these Centurion owners, shutting down for a few minutes to switch riders is no issue, it’s when you are full ballast and sitting for a lunch break or longer.

 

[anmut]

Someone posted this video on “passive hydro lock”

 

[swatski]

That’s what I was thinking. According to these Centurion owners, shutting down for a few minutes to switch riders is no issue, it’s when you are full ballast and sitting for a lunch break or longer.

I would say it is a very significant concern in our boats, indeed.
I have not had a chance to watch your video, yet. But this topic has been discussed, in general, if that's the same excat issue I don't know but there must be some overlap:

https://jetboaters.net/threads/hard-re-starting-list-side-engine-ballasted-ar240-wake-surfing.13897/

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[swatski]

Someone posted this video on “passive hydro lock”

great vid, thanks for posting, always a good reminder!
I will have to reread what was said on our boats, it's a little different exhaust system but the same concept.