Fulid master question

Lowes Fluid Master. Tank flapper, has a adjustment. Minimum maximum, (No instructions in box. Some on outside box). Here's my question, on our houseboat. I just. Installed a household commode, tips. To use minimum water going back in holding tank. I see there are 2 adjustments. One on the fluid master slide which controls water level in tank, I can make the shut off longer or shorter. I understand that. I don't understand. The flapper adjustment? Which has a adjustment like a sun dial. (Foremost is the commode clears solid. Thanks).

What is the sun dial adjustment control?

I think that is an adjustment for how quickly the flapper closes.

It controls how quickly the trapped air exits the flapper's bulb. The faster it leaves the quicker the flapper drops and the shorter the flush will be.

Each toilet has a sweet spot for how full the bowl is required to be when you finish refill, and the height of the water in the tank may have little to do with how much is actually used on each flush...they often use excess height to add more 'power' to the flush (think how a water tower works). But, getting the balance of how much it takes to refill the tank means getting the balance proper so that the bowl is refilled just at the same time, or you're wasting water. If there isn't enough in the bowl to start with (the refill didn't last long enough and the tank refilled too quickly), the toilet won't flush right - IOW, the balance of the water flow during refill must fill both the bowl and the tank at the same time. You only have control over when the tank is full. On some refill valves, the ratio of tank/bowl will never get the bowl full properly. On some fill valves, they have adjustments to help balance that flow...I do not think Fluidmaster has any that have this feature.

Trying to restrict the water use on a toilet not designed for it usually doesn't work well, if at all.

I hope some of you who responded are still reading, as u know a standard home uses a 4 " through the roof vent.
This unit is clearing itself on a vent line probably 3/4", (this vent is with in 6ft of the actual commode a through the hull vent on the side of the hull) this an off the shelve commode the low in, but works fine so I guess any tinkering I do may be risky....

The commode cleared itself on the very last flush as liquid was reaching the overflow. I really expected to lose some of my tank capacity, because of the venting issue,...anyway thanks for your input

What's the risk of tinkering?

Think of one control setting high tide in the tank, and the other setting low tide.

Unless the toilet is flushing into a "sealed tank", a vent, of any size, is NOT a necessity. And, a "standard home" toilet does NOT need a 4" vent through the roof, depending on the code it could be 1 1/2" or 2", but as a practical matter either one of those is also larger than "necessary".