I have a few concerns with regard to what is happening at Lenthall's, and eventually other dams which have had their administration handed over, and I'll try to sound slightly intellectual here.
It would be helpful if we were advised the reason for the HP limits. Is it pollution? If so, let's look at where the water is drawn for public use. I do not know where the actual water is taken for Wide Bay use, but I do no about Somerset and Wivenhoe. Somerset allows petrol motors with no overall speed restrictions. Ignore the 6 knot zones due to low water. Wivenhoe only allows petrol motors in an emergency, or if they are fitted to a trailer sailer type vessel. (Nup, dunno why they can use them!) All of the water from Somerset either goes to Kilcoy, for their public usage, (they musn't worry about the pollution aspect) or into Wivenhoe, which must have a special filter at the top of the dam to remove all the pollution before it hits Big W. The water then passes from Wivenhoe to either Esk, for public use, or down the Brisbane River to Mt Crosby. Between Wivenhoe and Mt Crosby, Lowood and Fernvale take their water, (and pump their treated sewage) but petrol outboards are again permitted on the river above where Brisbane draws it's water. I also draw your attention to the proposal from our State Government that a water grid be introduced so that water can be shared between dams in times of shortage. They must be fitting filters so the pollution from Boondooma, Bjelke Petersen, Borumba and Somerset does not get transferred to Wivenhoe and Hinze. My conclusion here is that "pollution from internal combustion engines" cannot be the reason for not permitting petrol engines.
Erosion! Perhaps this could look like a reason to someone who has not been on Lake Lenthalls, or any other dam. Erosion from power boats does occur as can be seen at Somerset Dam, but hang on, why is there the same erosion at Wivenhoe? Could it possibly be caused by wind and the common practice of clearing all trees from the banks during construction of the dam.
I've come to the conclusion that Water Corporations, they are no longer Government departments, find it difficult to administer the recreational usage on their dams. They obviously fail to see the income generating potential of recreational usage to small towns in the vicinity of these dams. Businesses Kilcoy, Esk and Fernvale obviously earn money from users of Somerset and Wivenhoe. (I buy at least one Fernvale pie every time I fish there!) They want to sell their water for the maximum amount of money they can get, with the minimum outlay. No public usage of the facility will see it much easier for them to accomplish this.
Bomber is correct. These impoundments were built with taxpayer's money. The administration of the water has been handed over to other enterprise, however I'm sure the actual dam must still belong to us, the taxpayers.
Unfortunately, my conclusions will never have a large influence on the Water Corporations. Maybe the only thing that will, is public safety. If I have to remove the motor from my boat to use Lenthall's, and I go for a fish, and all the Fernvale pies I've eaten catch up with me and I have a heart attack in my boat, where am I? My mobile doesn't work there, and I don't have a motor to get back for medical treatment in a timely manner. OK, I'm dead, and it's a tragedy, and I can't sue them, but maybe my family can. I hope so, because if it wasn't for their unjustifiable rules, I may still be alive.
My last thing is to liken these rules to road rules. How many Councils have a 50kph limit, and also direct that only 4 cylinder cars can use that street. It'd never happen on the road, but it may happen on our waterways.