2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Optimizing the performance of Boston Whaler boats
RandyV
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2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Postby RandyV » Sat Nov 05, 2022 3:16 pm

[For an OUTRAGE 18 with a 225-HP Mercury OptiMax 225-HP engine:]

Q1: would switching to a 15 x 15-pitch four-bladed propeller give the hull more stability?

Q2: would switching to a 15 x 15-pitch four-bladed propeller give the hull more lift?

Q3: would switching to a 15 x 15-pitch four-bladed propeller give the hull the ability to keep a constant boat speed of 20 to 22-MPH?


BACKGROUND: I have 2000 OUTRAGE 18 with a Mercury OptiMax 225-HP engine with a MIRAGEplus three-bladed 15.5-inch-diameter x 17-pitch propeller. The PVS vents are closed with solid plugs. The engine mounting height is three-holes-up from lowest position.

I have had this boat for eight years. I use it for angling on Lake Erie. Lake Erie often has "snotty" conditions. [Lake Erie is famous for being a shallow lake with a very long fetch possible, leading to wind waves of significant height and very short spacing--Moderator]

I have installed trim tabs on the OUTRAGE 18 hull. There is also an aluminum anti-ventilation plate foil extension of the type sold under the brand name WHALE TAIL XL STABILZER on the engine.

PERFORMANCE DATA

The Mercury OptiMax 225-HP engine can accelerate to 5,600-RPM, and the boat speed will be around 48-MPH, varying with the boat weight from loading.

The 225-HP engine is more power than I need. If I jam the throttle (to FULL from IDLE) the boat practically jumps out of the water. There is NO concern about the time to accelerate to plane from a standing start.

At times to go fast is fun, but I would not have a care if some of the boat's top speed were lost.

The boat's performance in calm condition is excellent. The boat's performance in "mid" conditions is excellent.

When there are choppy waves, I typically have to search for a boat speed that is the slowest on-plane boat speed, usually between 18 to 20-MPH. There is a tendency at that speed for the boat speed [to increases and for the boat to get more on-plane, resulting in a boat speed increase] to about 27-MPH or higher; for the wave conditions a boat speed of 27-MPH is too fast.]

As a result of the too fast boat speed, I reduce the throttle. The boat then ends up dropping off plane. Then the cycle starts over.

The engine speed seems to surge depending on how much forward pressure I am getting from waves.

SUSPECTED CAUSE OF INABILITY OF ENGINE TO MAINTAIN THE BOAT ON PLANE AT A SLOW SPEED
The Mercury OptiMax 225-HP engine is an excellent running engine. I believe [the problem with the inability for the engine and propeller to be able to maintain the boat on-plane in head seas at a modest just-on-plane boat speed is] all propeller-related.

Also, I do trim the motor and trim tabs to enhance the ride for the conditions as needed.

POSSIBLE ACTIONS TO BE TAKEN IN THE FUTURE

I may buy a HUSTLER brand four-bladed 15 x 15-pitch propeller.

I could change the propeller back to the MIRAGEplus 15.5 x 17-pitch propeller when I use the boat on smaller lakes

Since I did not install the trim tabs, I believe that without experiencing any loss of planing of boat control I could remove the WHALE TAIL foil extension appendage from the anti-ventilation plate

ASIDE: I have searched and can't seem to come to a conclusion on how to improve the performance I am trying to achieve.
Last edited by RandyV on Tue Nov 08, 2022 1:17 pm, edited 2 times in total.
2000 Outrage 18, 225 Optimax

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Phil T
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Re: 2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Postby Phil T » Sat Nov 05, 2022 5:10 pm

Reads as the engine is "one-hole up".

Engine should be mounted so there are two empty holes above the top bolt.
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Re: 2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Postby jimh » Sun Nov 06, 2022 2:02 pm

You need to read the article on engine mounting height nomenclature. All discussion of engine mounting height MUST uses the prescribed nomenclature for engine mounting height so that we do not have six or seven posts going back and forth trying to figure out what is the actual engine mounting height and there is a consistent method used.

Read at

Engine Mounting Height Nomenclature
https://continuouswave.com/forum/viewto ... ?f=7&t=739

Reply with ONE of the FIVE possible descriptions of engine mounting height given in the article.

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Re: 2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Postby jimh » Sun Nov 06, 2022 2:08 pm

The problem described is a common problem: in adverse head seas a moderate V-hull planing hull boat like a classic Boston Whaler, in this case an OUTRAGE 18, cannot be maintained at a comfortably slow on-plane orientation.

The reason for this problem is generally that the engine cannot produce sufficient horsepower at a particular engine speed necessary for the slower boat speed with the boat on plane.

The cause for this behavior is the engine has a narrow power band in which it can produce its rated power. At engine speeds below the rated power engine speed, the engine is not producing enough power to keep the boat on plane at a lower speed.

The term "power band" refers to a range of engine speeds under load and the amount of horsepower the engine can deliver into a load at those engine speed.

The best solution is to change to an engine with a much wider power band, but, of course, that is generally impractical and also very expensive.

And alternative approach is to change the propeller pitch to a lower pitch. The immediate effect of a lower pitch propeller will be that the engine speed will need to increase for a particular boat speed.

Also, whenever seeking advice about propellers, you must include the engine GEAR RATIO.

Because no gear ratio information was given, I will assume the gear ratio is 1.75:1. With this information we can look at the effect of a change in pitch of two-inches on boat speed.

First I will predict the engine speed needed for 20-MPH, assuming a 1.75:1 gear ratio and a rather large SLIP value. For a start I will use SLIP=25. I will use the PROPELLER CALCULATOR FOR MPH at

https://continuouswave.com/calculators/propCalc.php

The entered data will be

RATIO=1.75
PITCH=17
SLIP=25
MPH=20

The calculated value will be RPM. The calculator returns 2900-RPM.

Recalculating with PITCH=15 gives an engine speed of 3285-RPM.

The increase in engine speed to 3285-RPM from 2900-RPM should allow the engine to develop more power output. Whether or not the power output at 3285-RPM will be sufficient to maintain the boat on plane at 20-MPH cannot be predicted. The only real way to discover this is by testing a propeller.

Regarding effect on top boat speed, I would estimate that the boat should still accelerate to about 45-MPH with the 15-pitch, with the engine speed reaching 5900-RPM.

ENGINE AND TRIM TAB SETTINGS FOR SLOW PLANE
The typical moderate V-hull planing hull boat will be able to maintain a lower on-plane speed if the engine trim is set to the lowest possible position and the trim tabs are set for bow-down as needed.

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Re: 2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Postby jimh » Sun Nov 06, 2022 2:25 pm

RandyV wrote:[Q1: would switching to a 15 x 15-pitch four-bladed propeller give the hull more stability?
No, the hull stability is determined by the hull form, the center of gravity, and other hydrodynamic forces

RandyV wrote:Q2: would switching to a 15 x 15-pitch four-bladed propeller give the hull more lift?
The term "lift" in regard to the ability of a propeller to affect the height above the water that a particular boat will operate when on plane is very difficult to predict. Typically a propeller said to have good "bow lift" will have blades with significant rake back. Typically a propeller said to have good "stern lift" will have blades with very little rake back. Curiously, some propeller are said to deliver both "bow lift" and "stern lift" simultaneously. This talk of "lift" is seldom explained in any scientific manner, and propeller makers and propeller sellers use these terms without an explanation of how the lifting forces are created. This seems to work because boaters have no method of measuring "lift" unless they have a chase boat taking pictures of the boat in controlled conditions to allow comparisons. Without any controlled comparison method, the "lift" becomes something the boat operator senses, or more often, wants to sense after spending $600 on a new propeller.

RandyV wrote:Q3: would switching to a 15 x 15-pitch four-bladed propeller give the hull the ability to keep a constant boat speed of 20 to 22-MPH?
The hull's ability to be on-plane at a certain speed is fixed by the hull structure. What a smaller pitch propeller will change is the engine speed needed to maintain a certain boat speed. The engine speed will increase with decreasing pitch. This may result in the engine being able to produce the needed power to maintain plane at the chosen boat speed. See my earlier remarks.

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Phil T
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Re: 2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Postby Phil T » Sun Nov 06, 2022 2:28 pm

Discussing the appropriate diameter and pitch of propeller without including the specific name of the brand and model is meaningless.

Performance is not dictated by diameter and pitch alone and sizing is not universal.
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Re: 2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Postby jimh » Sun Nov 06, 2022 2:32 pm

RandyV wrote:[he Mercury OptiMax 225-HP engine can accelerate to 5,600-RPM at full throttle, and the boat speed will be around 48-MPH, varying with the boat weight from loading.
I am surprised that the engine speed is only 5,600-RPM and boat speed is only 48-MPH.

For comparison, I have a 225-HP engine and the same Mercury MIRAGEPLUS 17-pitch propeller. That combination can accelerate a much heavier boat (a REVENGE 22 W-T WHALER DRIVE) to 44-MPH.

I would expect an OUTRAGE 18 with 225-HP to be a rocket ship, hitting speeds well above 50-MPH.

I think the 17-pitch propeller is a bit too small for best top speed, and the engine is probably actually capable of a higher engine speed than the reported 5,600-RPM. I don't think you are reaching full-throttle and full 225-HP.

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Re: 2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Postby RandyV » Mon Nov 07, 2022 12:00 pm

Jim,

You are 100% on with respect to power band. Other than propwllwe selection, I had considered this as the possible main reason the engine seems to change apwws when trying to climb or come down from different waves with varying pressure on the hull. At the lower engine speeds, the torque is just not there to keep engine speed consistent.

My ignorance in how a lower pitch would affect rpm at a certain speed is what I was missing to get the rpm into or closer to the power band of that engine. Your scenario of switching to a 15-pitch makes perfect sense.

Are you also suggesting a four-bladed propeller of the same diameter as I have now?
2000 Outrage 18, 225 Optimax

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Re: 2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Postby jimh » Mon Nov 07, 2022 5:57 pm

RandyV wrote:JiM—are you also suggesting a four-bladed propeller of the same diameter as I have now?
Propeller diameter is not a particularly essential ingredient in propeller selection. Usually the propeller manufacturer selects a propeller diameter that is appropriate for the intended use of the propeller.

If you were to try a four-bladed propeller that was similar to the Mercury MIRAGEplus three-bladed propeller, you would probably try a REVOLUTION4 propeller. For a long time the REVOLUTION4 propeller was only made in a least-pitch value of 17-inches, but for your application you might try a 15-pitch REVOLUTION4 propeller.

The REVOLUTION4 propeller has a lot of blade area and it represents a significantly higher load that a MIRAGEplus three-bladed propeller.

Also, we still need you to clearly state the present engine-mounting height using the number of holes-up-from-lowest description method.

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Re: 2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Postby RandyV » Tue Nov 08, 2022 11:30 am

Sorry about the position description. The ENGINE MOUNTING HEIGHT is three-holes-up from lowest position.

I have done a lot of reading on [the problem of the boat not being able to stay on plane at low speed]. I have a feel for the direction I need to go. However, two different propeller specialists have told me a vastly different solution.

One propeller specialist recommend changing to a Powertech OFS4 with 13-pitch; another propeller specialist recommended changing to an OFS4 17-pitch.

When people that work for companies who claim to be propeller experts are so far apart, it makes me rethink what I have read and what I think I have learned . After all, I am just a boat owner who loves to go boating and angling.

I believe your suggestion of 15-pitch aligns best with what I think I have learned and the results I am trying to achieve. I was leaning toward a four-bladed propeller,. So my only apprehension at this point is do I go three-bladed or four- bladed; and is a four-bladed propeller too much surface areas?
Last edited by RandyV on Wed Nov 09, 2022 6:46 am, edited 1 time in total.
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Re: 2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Postby Phil T » Tue Nov 08, 2022 12:43 pm

Who, specifically gave you each recommendation?

I recommend a four-bladed propeller. The PowerTech OFS4 is a good model.

I trust Ken Reeves at PropGods.com. Give him a call. He also takes back a propeller for exchange for a nominal stocking fee. So few sellers of propellers will do this anymore.
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Re: 2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Postby RandyV » Tue Nov 08, 2022 1:25 pm

I didn't want to call out companies that have conflicting [propeller selection advice] and possibly disparage their names.

http://PropGods.com: PowerTech OFS4 in 17 pitch. This propeller ships about four weeks after you order. If you don't like it, you can return it for $40 plus shipping. It is said to be a good stern-lifting propeller. The PowerTech OFS4 should hold the OUTRAGE 18 boat on plane at slower speeds and will help keep the the bow more down.

http://PropellerPros.com: PowerTech OFS4 in 13-pitch
Last edited by RandyV on Wed Nov 09, 2022 6:44 am, edited 1 time in total.
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Re: 2000 Outrage 18 with 225-HP Cannot Stay on Plane at Low Speed

Postby jimh » Tue Nov 08, 2022 5:43 pm

RandyV wrote:The ENGINE MOUNTING HEIGHT is three-holes-up from lowest position.
Engine mounting at three-holes-up from lowest is a rather high engine mounting height.

Consider what happens to a stern-lifting propeller as the engine mounting height is raised higher and higher: more of the propeller becomes closer to the water surface and at extreme heights perhaps the blade tips of the propeller will be breaking out of the water a bit on the upper segment of their rotation. Will this help or hinder the stern lifting effect that is claimed to occur?

The PowerTech OSF4
I have never tested a PowerTech OSF4 propeller so I have no first-hand comments. I do like the resilient hub coupling system. It looks akin to something Mercury has been using to reduce propeller KLUNK and VIBRATION. The constant diameter at 15.5-inches is also interesting. Some propeller model series retain a constant diameter and only change the pitch.

MAKING PRODUCTION CAST STEEL PROPELLER
I think that propellers in a model series with a constant diameter and only a pitch change may be using the same blade molds for every model, and just changing the angle which the root of the blades are attached to the hub. In casting stainless steel propellers, the production method often uses a wax-plug for the HUBB section, and then three or four identical molds to make each individual BLADE wax-plugs.

A skilled artisan then carefully attaches the individual three or four blades of wax-plugs to the hub wax-plug, using wax and heat to join them. The joint line is then sculpted to the final appearance by eye and the skill of the assembler. These four or five piece wax plugs are hand-assembled into one complete wax for each propeller to be made. Then they are put into a sand flask and packed with sand with a binding additive. When the propeller is cast, the melted steel replaces the wax in the sand mold.

Perhaps the hub wax-plug changes for each pitch, giving the artisan attaching the blades a guide for exactly what pitch to attach them to the hub.

Making production cast steel propellers is done like this, so the accuracy of the pitch and balance of the final molded propeller depends very much on the skill and finesse of the artisan who attaches the wax blades to the wax hub by hand. I also suspect that cast propeller are checked to confirm the proper pitch, to a degree. The added premium cost for "lab-finish" may include a slight tweaking of all the blades for identical pitch and balance on the cast propeller to bring them to precise position.