When riding on a lake do you keep the prop all the way down or trimme up. Seems like every manufcturer recommends differenty. what do U do
Depends on wave actions. Lots of waves, trim in to keep bow down for smoother ride and control. If flat lake, I trim up slowly until it makes an odd sound meaning the prop is up too high but not breaking the surface. You'll know the sound once you hear it. There's a technical name for this sound and action but have forgotten it.
The object of "trimming" your engine or outdrive up/out, or in/down is to decrease or increase the amount of "wetted surface" of the hull in the water. The larger the surface area of the hull that the engine has to push through the water, the slower you will go and the more fuel you will consume. Sea/weather conditions and the loading of the vessel are the two major variables to consider when trimming. In calm or light seas with an average or light load, once on plane, trim your engine/drive out. You will feel the bow rise and an increase in speed. If the prop "blows out", you will hear the engine rpm increase and the boat will slow down. This means that you have trimmed the drive too far out. I recommend trimming all the way in, easing the throttle forward to wide open, then once established on plane, ease the throttle back while simultainiously trimming out to a comfortable rpm/hull speed for you. Play with it and see what works best for your boat. If the boat starts to porpoise(sp?), then trim in a little.
I keep the props down. If i ajust stern drives to high i can ruin the gimbal bearings. My boat has trim tabs which I use. Not sure if you have stern drives or outboards.
At its simplest, trim in while accelerating from a stop. This pushes the bow down, gets you planing faster. Once on plane, trim out a little for best efficiency.
How much to trim out? Depends. To gain experience, watch your tachometer. Without adjusting the throttle, adjust the trim out. You'll see RPM and speed increase without adding more fuel.
If you trim out way too much, you'll hear the prop sucking air--ventilating.
But, if its choppy, you may want to forego max efficiency in favor of a smoother ride, and keep the bow down ( trim in). This usually results in a wetter ride as well.
Trim tabs are great for adjusting bow-down trim. But they have no effect on bow up trim. A sterndrive or outboard can change both.
Practice--"best" trim will change with the day, the conditions, and your course.