Andy wrote: ↑17 Feb 2019, 16:23
I would imagine, but no doubt they will come back on this, that for most general duties youll keep the trim the same, for one person, but you have the option to change the trim to the weather conditions. No doubt someone will tell me off if i am wrong, and if the weight is placed in a different way, eg if you put 2 people up front, rather than one person only, then you can mess round with the way the boat handles. More weight at front more trim on the engine, so it planes better. Think I got that right ?
Andy your not that wrong there mate.
Started bashing out a reply but got bored, so lifted this rather long condescending but fairly comprehensive description off tinternet;
USING POWER TRIM
Positive and negative trim – what’s that?
Modern outboard and sterndrive engines have a power trim and tilt system that allows you to adjust the trim, or fore and aft running angle of your boat while underway. Adjusting this trim or hull running angle to suit changing sea, wind and current conditions will improve your boat’s handling, ride and economy.
You might wonder why changing the trim of your boat is even necessary — assuming your boat has been well designed in the first place. However, even the best of planing hulls will benefit from the use of power trim.
The first thing to learn is that changing the drive angle of your outboard or sterndrive leg will change the trim of your boat when it is running at speed.
Trimming or lifting your outboard leg up will trim the bow of your boat up. This is known as positive trim. Trimming your outboard full down or “in” is known as negative trim. This action will encourage the bow of the boat to push down further into the water.
If you think about the angle of the engine drive leg and the thrust of the propeller it is quite logical.
With the engine drive leg trimmed all the way down, the propeller is pushing or thrusting in a diagonally upward direction, and this lifts the stern of the boat up, which in turn drives the bow of the boat down. When you trim the drive leg up, the opposite occurs.
In nutshell, all you need to remember is that trimming the engine up or “out” will lift the bow up. Trim it down or “in” and the bow goes down. In most sea conditions, modern boats perform best with the outboard set so that the boat has a slight bow up running attitude.
That said, when taking off from displacements speeds, many boats will perform better with the engine and the bow trimmed down. This allows the boat to rise quickly onto the plane. Once the boat is up and running, however, the trim of the boat should be adjusted to suit the specific sea conditions.
Leaving the engine and the bow trimmed full down can cause the boat to handle poorly. If the bow is digging or ploughing through the water, the steering will stiffen up, boat speed will drop, fuel consumption will increase, and a lot of spray will be pushed out from the bow of the boat.
Running the boat with the bow full down is also potentially more dangerous than a bow up attitude, given that when running downwind or before the sea, it can encourage a broaching situation.
Having made these comments, trimming the bow full down can make your boat ride more comfortably through the water, particularly when running upwind or into the sea. Trimming the bow down allows the sharply angled forefoot of the bow to cut, like a knife, through the chop, improving ride comfort.
Conversely, trimming the bow up is important when running downwind or in a following sea to keep from broaching. In normal running conditions, however, it can be inefficient to trim the boat up too high. The boat will have trouble getting onto the plane, it may ride harder, be inclined to leap off waves, and it could also develop a porpoising or bouncing action, even in calm water.