2005 190 NANTUCKET VERADO 150

Optimizing the performance of Boston Whaler boats
NoProblemo
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2005 190 NANTUCKET VERADO 150

Postby NoProblemo » Sun Jun 12, 2022 5:49 pm

My 2005 190 NANTUCKET has a Mercury VERADO 150 engine with a Mercury MIRAGEplus 17-pitch three-bladed propeller with the Mercury Performance Vent System (PVS) with "holes." I use the 190 NANTUCKET in coastal New England.

I read some [unspecified prior discussions and deduced that ] a Mercury REVOLUTION4 17-pitch four-bladed propeller will be better for ocean conditions and rough conditions.

Q1: should I replace the MIRAGEplus 17-pitch with a REVOLUTION4 17-pitch?

[Moved to PERFORMANCE for discussion--Moderator]

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Phil T
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Re: 2005 190 NANTUCKET VERADO 150

Postby Phil T » Sun Jun 12, 2022 5:52 pm

The Verado 150XL was an option starting in 2006. It came with the MIRAGEplus 17-pitch and 15.5-inch diameter

Have you tried running the boat with the PVS vent plugs in and out to determine the difference?

You may want to run the boat for the season before a $750 prop change.
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jimh
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Re: 2005 190 NANTUCKET VERADO 150

Postby jimh » Sun Jun 12, 2022 6:11 pm

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 MIRAGEplus. This is because the blades on the REVOLUTION4 are the same size or area as on a MIRAGEplus. In my experience, if you were running a MIRAGEplus 17, changing to a REVOLUTION4 15-pitch will probably be more appropriate. This became so obvious that Mercury had to start making the MIRAGEplus in 15-pitch.

The only way to get a REVOLUTION4 to turn at the same engine speed as a MIRAGEplus 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 MIRAGEplus.

In my article on propeller power curves I deduced the power curve for a REVOLUTION4 compared to a MIRAGEplus of the same pitch:

Image
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 MIRAGEplus 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 MIRAGEplus 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 MIRAGEplus 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.

NoProblemo
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Re: 2005 190 NANTUCKET VERADO 150

Postby NoProblemo » Sun Jun 19, 2022 11:43 am

First thanks, for moving the post to the correct spot. And for the help.

jimh--are you saying just run the propeller I have ?

jimh--or, are you saying that a REVOLUTION4 15-pith will work with my engine in the same engine [mounting height] as now?

This is all really new to me.

I would [like to alter the boat performance by changing the propeller to] get:
  • less propeller ventilation in rough water
  • the boat to remain on plane at a lower boat speed
  • the boat to accelerate to plane faster.

I can run the as-is--if the stock set-up is best for the boat and engine compared to modifying it. I'll survive.

jimh
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Re: 2005 190 NANTUCKET VERADO 150

Postby jimh » Sun Jun 19, 2022 2:08 pm

Here are two follow-on questions directed to me, and my replies.
NoProblemo wrote:are you saying just run the propeller I have?
It is not clear to me that you have already run the boat extensively with the current MIRAGEplus 17-pitch propeller. My inference from your earlier narrative was:
  • you have not run the boat very much,
  • that you have read somewhere that you must ditch the MIRAGEplus propeller and get a REVOLUTION4, and
  • that you think you ought to get a REVOLUTION4 17-pitch.

My first reply is, yes, you need to run the boat as now set-up, and discover if there really is some glaring defect in the boat performance. Also, you need to establish benchmarks for all the elements of the boat performance you think are going to be changed by just changing a propeller. Without that data recorded, you will never have any basis to know if a propeller change make any measurable difference.

NoProblemo wrote:or, are you saying that a REVOLUTION4 15-pitch will work with my engine in the same engine [mounting height] as now?
Based on my prior experience with the REVOLUTION4 17-pitch propeller, as I documented in the article on propeller power curves, the engine horsepower needed to turn a REVOLUTION4 is going to be greater than the horsepower to turn a MIRAGEplus of the same pitch. I thought made that clear earlier. I hope it is clear now. That's from my experience.

The REVOLUTION4 is a very large propeller, with blades with a lot of area, and it will be harder to turn than the three-bladed MIRAGEplus propeller of the same pitch.

I cannot predict what is going to happen with a REVOLUTION4 on your boat because you have not given any data about what is happening with the MIRAGEplus .

NoProblemo wrote:I would [like to alter the boat performance by changing the propeller to] get:
  • less propeller ventilation in rough water
  • the boat to remain on plane at a lower boat speed
  • the boat to accelerate to plane faster.
Those are all nice improvements to get from just changing the propeller. I don't know if you can make all that happen.

A propeller ventilates when it pulls air down from the water surface into the propeller blades. The best way to suppress that is to immerse the propeller more deeply in the water.

A boat remains on plane at lower boat speeds only if the ENGINE can produce the needed horsepower at that particular engine speed. The usual reason a boat won't stay on plane at lower boat speeds is that engine just does not have enough power at the engine speed needed to be maintained to keep the lower boat speed constant. This can be changed by going to a propeller with LOWER pitch, which will then need to be turned faster at the same boat speed needed to hold plane. The engine will be turning faster, and the engine MAY be able to produce more power at the faster engine speed and keep the boat on plane. The real problem is with engines that do not have a wide power band and cannot produce significant engine power output at lower engine speeds.

To get faster acceleration, there are two ways: get a more powerful engine, or reduce propeller pitch.

NoProblemo wrote:I can run the boat as-is--if the stock set-up is best for the boat and engine compared to modifying it.
If the boat came from Boston Whaler rigged with the engine and propeller, there is very good reason to believe that Boston Whaler thought the combination of engine and propeller was the best set up.

Before you spend $750 because somewhere you read you should get a REVOLUTION4, why not run the boat for a few weeks and see what happens without changing anything?

jimh
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Re: 2005 190 NANTUCKET VERADO 150

Postby jimh » Sun Jun 19, 2022 2:18 pm

MORE ON PROPELLER VENTILATION

Propeller ventilation is often actually induced by the engine. If the engine controller is not designed to maintain a constant engine speed at a constant throttle setting, when a propeller initially begins to ventilate the engine may accelerate due to a load reduction from the ventilation. When the engine accelerates, in makes the ventilation worse, causing more ventilation. Soon the propeller is completely ventilated.

In contrast, an engine with an engine controller that tries to maintain a certain engine speed at a particular throttle setting will work to avoid ventilation. If a propeller does have some initial ventilation, by maintaining a steady speed and not accelerating, the engine will not enhance the ventilation. This allows the propeller to clear the ventilation itself and get back to working in solid water.

Modern engines with engine speeds controlled by engine control units will usually not accelerate and run-away to higher engine speeds due to a momentary propeller ventilation.