1982 OUTRAGE with HONDA BF150

[KARLOW]

Give me a recommendation for a propeller to fit a c.2012 HONDA BF 150 that I rebuilt in 2022 that is used on an 1982 OUTRAGE [and later identified an an OUTRAGE 18].

The engine currently has [some sort of propeller described as stainless steel 17-pitch].

BACKSTORY

This OUTRAGE [18] has two Group 27-case-size batteries in the console, and two Group 24-case-size size batteries in an ice chest in front of the console.

This has a leaning post, and under the leaning post is a 25-gallon capacity bait tank.

This OUTRAGE [18] also has bottom paint.

[Please start a new thread for you new topic on a completely different topic--this thread will only discuss performance of the boat with its unknown propeller.]

[Phil T]

If I had to guess the prop is possibly a Solas.

We need to know the engine mounting height. How many empty holes are above the top bolts? What is the wide-open-throttle (WOT) rpm at top speed with a typical load?

My list for the Outrage 18 with the Honda BF 150 includes**:

Honda "Turbo" 14-1/4" x 17, 1 hole up
Stiletto Advantage II 14-1/4" x 17* See http://continuouswave.com/ubb/Forum4/HTML/005027.html
Power Tech 15.25X 16 pitch 4 blade
Honda "Turbo" four blade, 14-1/4" x 15" (#58234-YZ3-A15H)

With all the batteries you may need to drop 2" of pitch in the specific models listed.

** Size only applies to the listed make and model of prop and is not transferrable.

[jimh]

To help you with propeller selection will be difficult until you identify the boat length.

PHIL T seems to think it is an OUTRAGE 18, but he is a better mind reader than most.

Q1: do you have an engine speed gauge (tachometer)?

Q2: do you have a boat speed gauge (often a GNSS receiver with speed over ground)?

Q3: have you collected any data about the performance of the boat with the current propeller?

To see what sort of data should be collected, read the article at the top of this forum with the TOPIC line

PROPELLER TESTING: What Data to Collect; How to Evaluate the Date
https://continuouswave.com/forum/viewto ... f=7&t=7196

Q4: why are you searching for suggestions for a new propeller?

Q5: what do you think is wrong with the current propeller?

Q6: can you look at the current propeller and find any identifying marks that would help readers to know what the current propeller brand, model, pitch, diameter, number of blades, and metal composition actually is. Saying the propeller is some sort of stainless steel 17-pitch only gives two pieces of information.

Q7: how about giving the number of blades, the diameter, and anything else you can get from the propeller itself?

Q8: what is the gear ratio of the engine?

Q9: what is the maximum engine speed recommended for full-throttle operation?

Q10: does the manufacturer recommend a specific engine speed range as the optimum engine speed range at full-throttle?

[KARLOW]

Sorry for the omission, the boat under discussion is a 1982 OUTRAGE 18.

The HONDA BF 150 is mounted as high as possible, and there are no concerns about that mounting height.

[Moderator's note: we don't know the details of the mounting bracket so this engine could be mounted three-holes up or four-holes up. Please describe the mounting height using the number of "holes" above lowest possible engine mounting height.]

Typical use for this OUTRAGE 18 is inshore or not more than 30 miles offshore, often in seas of two to three feet.

The cruising speed is 18 to 20-nautical-miles-per hour.

The live well tank is not always in use.

The typical fuel load is 50-gallons at departure from the dock.

Here is some performance data:

PROPELLER: 14.25 x 17-pitch Michigan RAPTURE stainless steel model 0033074
With two aboard the OUTRAGE 18 gets on plane in four seconds and does not dig a hole.

Some engine speeds, boat speeds, and fuel flow rates

RPM    NMPH  GPH
4000   20.9.  
3900         6.8
4150   21.4

[jimh]

REPEAT QUESTIONS:

Q5: what do you think is wrong with the current propeller?

Q8: what is the gear ratio of the engine?

Q9: what is the maximum engine speed recommended for full-throttle operation?

Q10: does the manufacturer recommend a specific engine speed range as the optimum engine speed range at full-throttle?

[Phil T]

The wide open throttle (WOT) rpm range for the BF150 is 5000-6000.

Q11: What is the engine speed at full throttle when the boat is lightly loaded?

[KARLOW]

I'm sorry I don't have any addition performance data currently. I'm looking for better performance which is better fuel mileage mainly between 18 and 22 knots. and good performance at slow troll speed. I tried a four-bladed propeller, but it was too noisy at trolling speeds. It makes the whole boat resonate.

[Phil T]

We are asking the questions to get you answers.

We pick propeller that are good for MPG but also good for all speeds.

If you select a prop that is only good between 18 to 22-nautical-miles=per-hour, the engine will have operational problems.

Propeller selection is make and model dependent. One four-bladed propeller is not the same as the others.

Q12: what four-bladed propeller model and size did you try?

Q13: what hub was installed in the propeller?

Describe the boats performance and the resonance you experienced.

[jimh]

I'm looking for better performance which is better fuel mileage mainly between 18 and 22 knots. and good performance at slow troll speed.

Okay, now we can help you with a new propeller recommendation because we have an idea of your goal.

For best fuel economy you probably should try a three-bladed large-diameter propeller with considerable blade area, such as a Mercury MIRAGEplus . Fuel efficiency is generally related to big blade area, very little blade rake, good blade design (with very sharp trailing edges), and thin blades.

I tried a four four blade propeller, but it [was] too noisy at troll speeds. It makes the whole boat resonate.

The four-bladed configuration in a propeller on an outboard engine means that TWO blades will SIMULTANEOUSLY pass into the shadow of the gear case and the skeg. When a propeller blade is in the shadow of the gear case or the skeg, it does not get the same water flow as when not in the shadow. The result is an influence on the engine instantaneous propeller shaft velocity, because there is a REDUCTION in the loading on that blade. On four-bladed propellers there are only TWO shadow events per revolution, so the FREQUENCY of these instantaneous changes in the propeller shaft velocity is LOWER, but the amplitude is HIGHER because two blades are involved simultaneously.

With a three-bladed propeller each blade passes through the shadow of gear case and skeg separately, so there are SIX shadow events per revolution, and the amplitude is LOWER because only one blade is involved with each shadow event.

Exactly how the whole boat will be EXCITED by these vibrations depends on many factors, so in some instances a four-bladed propeller might REDUCE vibration and in other instances a four-bladed propeller might INCREASE vibration. Which effect occurs depends on the propeller rotation speed, the frequency of shadow events per revolution, the coupling of the engine to the transom, and any resonances in the boat itself.

WHAT EFFECTS FUEL EFFICIENCY

The engine "sweet spot" is when the Brake Specific Fuel Consumption (BSFC) peaks at a certain engine rotation speed and power delivered into the load. Real engines have curves of the engine BSFC, but recreational outboard engines do not provide any data. BSFC is measured in pounds of fuel consumed per horsepower delivered.

A best guess approximation for optimum BSFC is generally at an engine speed of about 75-percent of maximum to 85-percent of maximum. In the case of a BF150, if it can run at 6,000-RPM, then the optimum engine speed range for best BSFC might be 4500 to 5100, but that is just a wild guess. HONDA should really TELL you what the optimum BSFC engine speed range will be.

The other factor is the boat speed and the design of the propeller. The propeller efficiency is not constant; it varies with the speed of motion through the water. The rate of rotation of the propeller relative to the engine speed of rotation is a function of the gear ratio.

In summary, to get the best fuel economy the propeller efficiency and the engine efficiency should PEAK at the same boat speed and engine speed. There is NO WAY to calculate this for a particular boat with a random engine and random propeller.

Again, try a large-blade-area three-bladed steel propeller with thin blades and not much rake with good blade design with cup and sharp trailing edges, otherwise known as a Mercury MIRAGEplus or similar design, and choose a pitch that is appropriate for the engine, gear ratio, boat, and loading.

[KARLOW]

Q14: what is the difference between a MIRAGEplus and a VENGEANCE prop?

Q15: what is the expected performance with a MIRAGEplus 17-pitch on my boat?

Q16: what is the expected performance with a VENGEANCE 17-pitch on my boat?

[jimh]

Q14: what is the difference between a MIRAGEplus and a VENGEANCE propropeller?

VIsit the Mercury propeller website to read about the difference between those two Mercury propeller models.

https://www.mercurymarine.com/en/us/pro ... rt-series/

A principal difference is the VENGEANCE propellers do not have the Performance Vent System. The MIRAGEplus propeller have the Performance Vent System.

For boats whose top speed potential is under 60-MPH, I doubt the Performance Vent System has any useful application.

The VENGEANCE propeller is also the least expensive stainless steel propeller made by Mercury.

The MIRAGEplus is the most popular Mercury propeller. There is probably a reason for that.

[KARLOW]

I have been to the site. It's not very useful. Strangely enough, it does not say much. They recommend both props for most of the same applications. Other than the vents that can be used to tune hole shot, There are no details. It does not indicate why you should select one vs the other. It does not indicate why they make two 17" pitch pops for mid size outboards. Did I miss that section on there website?

[jimh]

My theory about Mercury propellers: because they make about 20 different lines of propellers with dozens of pitch and diameter combinations in each lines, there MUST be something they make that will work well, and it is just a matter of finding the right model and pitch.

I can't offer any advice about the VENGEANCE propellers because I have never used one, and I don't even recall anyone I know using a VENGEANCE propeller.

There is a comment on-line somewhere from a boater who says the VENGEANCE propeller is just a stainless steel version of an aluminum propeller that Mercury was (or maybe still is) making, and it was just offered as an upgrade path from the aluminum version. Again, this is just something some boater said, and I have no idea if that is correct.

When I earlier suggested you try a MIRAGEplus propeller, that was based on my own experience with them and the very good fuel economy they can produce (and have produced for my boat and engine), and also based on your statement that one of the desired outcomes in selecting a new propeller was better fuel economy.

At today's prices, a new Mercury stainless steel propeller is going to cost over $600. You need to work with a propeller seller who will let you water test a propeller and take it back with only a small handling fee and allow you to try another propeller. Typically the seller retains the original sales payment to bind you to eventually buying some propeller at the end of testing.

Another way to test propellers is to buy used propellers that are in very good condition. They can be bought for much less than a new propeller from a retail seller.

[Phil T]

We don't even know what propeller you have now.

Q17: Have you tried any of the recommended props I listed?

You mention trying a four-bladed propeller without the model name or size, so we have no way to evaluate it as to it being a good propeller for that boat-engine combination.

You need to understand that each propeller model is unique.

Size is not universally linked to performance.

Just saying "improve efficiency" is like saying "I want to go boating."

Q18: what is your fuel efficiency now?

Q19: how much is "better"?

Without some serious analysis of your current boat-engine-propeller setup now, any effort to improve performance is going to be unsuccessful.

I am not spending any more time on this topic till you do your homework, and answer the questions asked.

[KARLOW]

[In reply to one of 19 questions asked so far, this answer is provided:] Not yet.

My [1982 OUTRAGE 18] has been a trailer queen.

I have purchased and installed a VENGEANCE [of unspecified pitch] propeller, but I have not tried it. I will report results when I get some.

I will watch for a used [a MIRAGEplus propeller at a good price.

Thanks for the assist.