Buy a tachometer, otherwise you pretty much have to buy a bunch of props.
The fewer blades generally make for higher speeds as there is less drag, more blades are usually for more “bite” at lower speeds, high thrust props for example will have more blades.
However four blades props are generally thought to give the stern more lift
, or hold the bow down, same thing.
Those wings on an outboard are a patch at best, they correct for an incorrect setup. They work
by generating lift
, which raises the stern, lowers the bow, but if an engine
is trimmed correctly and the boats CG is correct, they are not needed and are only excess drag.
Ever wonder why no engine
is supplied from the factory with them installed?
If your dinghy is a center console and you cannot move your weight forward, that is when you need to go with a Dolefin or similar, but fixing the proposing etc with the engine height and trim being correct and the boats CG being correct is the best way.
I bought this tach for my motor
and used it to ensure my prop was correct, but it’s also an hour meter and I can schedule services based on operating hours, I also put on on my Honda generator
You would think these high dollar, electronic controlled engines would have an hour meter that the user can access. The engine ECU tracks hours, but only the dealer can access it.
Planing your big dinghy with 4 to 6 people and gear
with only 20 HP is going to be tough, you will likely need a prop that with only one person that you will hit the rev limiter.