By Thomas P.

Revolution is a 4-blade propeller, designed to run close to the sea surface and operate very well even with small amount of water, a fact that makes it perform very well in high engine’s mounting heights as well as in excessively elevated trim settings of the engine.

Revolution 23΄΄

The features of Revolution fit very well with the stepped hull of SeaDNA 999 and the only thing we have to think about is the mounting height of the engines on the transom, which in this case depends absolutely on the use of the intended rib.

On the small brackets of 12 cm, two new 300hp Verados were mounted with the reinforced lower units and gear ratio 1.85:1.

Revolution 23΄΄

We chose these loads on our test because this is the way the owner usually uses his rib.

Looking at the numbers in the above table we see that the cruising speed at low and medium rpm is not satisfactory for the particular engine-boat combination.

Assessing the behavior of the rib with the particular loads we noted:

  • fairly significant lag concerning the time of plane
  • relatively slow accelerations and poor throttle response at low rpm
  • that we were unable to trim out the engines a lot.

All the mentioned above lead to the conclusion that we need to lower the engines by about one hole so as to get better numbers with the specific loads.

Certainly, if the owner used the rib with fewer loads we would not need to lower the engines since the performance in this mounting height would be much better.

But in our case, with the specific loads, lowering the engine by one hole is necessary.

In this way, we will see significant improvement in cruising speed due to reduced slip, reduce of the fuel consumption and reduce of the time which the rib needs to get on plane, reduce of the rpm that the rib stays on plane, greater explosiveness and throttle response at low rpm and greater control of the bow.
All these we will particularly appreciate when traveling in bad weather conditions.

The engine’s rpm is indeed very likely to remain at the same level because the rpm that will be lost by lowering the engines will be replaced by the ability we now have to trim out the engines much more.

Revolution 23΄΄

...keep Ribbing!