I have run in large ocean nearshore breaking or curling waves of height greater than six feet--thankfully going downwind--on an OUTRAGE 25 with twin engines with Mercury propellers with PVS vents with the plugs having some opening. I don't recall what size opening. Control of the engine was awful. The boat felt like there was a rubber band that had to be wound up before the propellers would produce thrust. I suppose you get used to this, but it was very annoying.
In my opinion the PVS is a gimmick for 80-MPH bass boats to fool with so they can run propellers with very large pitch, eventually get up on plane on a small step at the rear of the hull, and turn propellers with 27-inch pitch and wind out the engine to 6,000-RPM and get a couple of MPH more boat speed and bragging rights among other high-speed anglers.
The Mercury PVS system is generally of no use on boats that run under 50-MPH. If your boat is set up with PVS vents with openings, get the full plugs, close the holes, and test with them.
If you plan to run offshore in big ocean waves, I would be most concerned about avoiding propeller ventilation. This may require that you keep the engine mounting height at a moderate rise from lowest position, maybe one-hole-up at the highest.
Regarding changing to a REVOLUTION4 propeller. I have tested a REVOLUTION4 propeller. For a long time the lowest pitch available was 17-inches. The propeller load on an engine of a REVOLUTION4 is much greater than a MIRAGE
plus. This is because the blades on the REVOLUTION4 are the same size or area as on a MIRAGE
plus. In my experience, if you were running a MIRAGE
plus 17, changing to a REVOLUTION4 15-pitch will probably be more appropriate. This became so obvious that Mercury had to start making the MIRAGE
plus in 15-pitch.
The only way to get a REVOLUTION4 to turn at the same engine speed as a MIRAGE
plus of the same pitch is to raise the engine mounting height so the upper blade tips of the REVOLUTION4 are running out of the water. Otherwise the engine power needed to turn a REVOLUTION4 with the engine mounted so the blades are in the water all the time will be significantly more than with a MIRAGE
plus.In my
article on propeller power curves I deduced the power curve for a REVOLUTION4 compared to a MIRAGEplus of the same pitch:
Fig. 1. Propeller power curves for several propellers.If you are not familiar with propeller power curves, the plot shows the horsepower need to turn the propeller. It show that for the engine to turn a REVOLUTION4 to 6,00-RPM requires 440-HP compared to turning a MIRAGE
plus to 6,00-RPM needing only 300-HP. To understand how the data was developed, read the full article.
I have been using a Mercury MIRAGE
plus 17-pitch propeller for many years, and the PVS holes have always been plugged. My boat's top speed is about 44-MPH. Even though in my situation the engine mounting height is quite elevated (due to having a Whaler Drive), the propeller provides very good grip. However, part of the ability of any propeller to ventilate easily comes from the outboard engine. Modern outboard engines are controlled by processors that set the engine speed. The result of this control is that the engine does not tend to respond to change in propeller load on its own, that is, if the propeller load begins to decrease, the engine won't increase speed on its own. This is important in stopping propeller ventilation.
When a propeller starts to ventilate--to draw air into the water from the surface--the propeller begins to turn in aerated water. To turn a propeller in aerated water is much easier for the engine than to turn the propeller in non-airy water. Older engines without strict engine speed control from their engine control unit would tend to respond to the decrease in load by increasing engine speed. A propeller spinning faster draws in more air into the water, and very quickly the propeller has ventilated and lost thrust. With a modern engine the engine speed remains constant, and this reduces the opportunity for ventilation to become more severe.
I have run my boat in very rough seas with the MIRAGE
plus propeller without any problems with ventilation. I cannot recall a single instance of the propeller ventilating to the point where the I had to reduce engine speed to get the propeller to resume normal thrust.
Another problem with the REVOLUTION4 propeller: it is very heavy. You will need to get a cushioned hub insert in order to stop the CLUNK from shifting into gear from neutral with this very heavy propeller.
Regarding propeller endorsements: my observation is once a boater spends $750 on a new propeller, there is a very strong tendency to find that the new propeller improved something compared to the old propeller.