23 CONQUEST Twin Yamaha F150 Engines

Optimizing the performance of Boston Whaler boats
ivansfo
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23 CONQUEST Twin Yamaha F150 Engines

Postby ivansfo » Thu Oct 14, 2021 12:53 pm

I decided to re-power my 2001 23 Conquest with twin Yamaha F150 engines. A deposit was made in November 2020, and 11 agonizing months later, the new engines have finally been delivered and mounted, as seen below.

23ConquestF150-1b.jpg
Fig.1. New Yamaha F150 engines installed on 23 CONQUEST
23ConquestF150-1b.jpg (36.88 KiB) Viewed 31200 times


23ConquestF150-2b.jpg
Fig. 2. View from astern.
23ConquestF150-2b.jpg (47.87 KiB) Viewed 31200 times


The Yamaha F150 engines have a gear ratio of 2:1. The F150 engines produces a propeller shaft horsepower of 150-HP at an engine speed of 5,500-RPM, and the recommended full-throttle operating range is an engine speed of 5,000 to 6,000-RPM. The engines are mounted in the lowest position possible. The PORT engine is a counter-rotation model.

[Moderator's note:I have added information to this initial thread which was elicited by a lot of back and forth questioning in follow-up posts, and those six or seven posts for the sake of clarity have all been deleted. When soliciting propeller advice the engine gear ratio and engine recommended full-throttle engine speed range are critical specifications to provide to readers.]

Now I need propellers.

Please give me a short list of propellers to use with these engines on a 23 CONQUEST.

The dealer who installed the engines has ordered a set of temporary 17-pitch aluminum propellers for he and I to test with the boat. We are awaiting these test propellers. Once we have these test data with the 17-pitch propellers, he plans to order a final set of propellers from Power Tech. He hasn't shared with me the exact model by Power Tech model but I told him that my preference would be four-bladed stainless steel propellers. Before he orders the final propellers, I want to be confident in his decision.

MORE DATA
This 23 Conquest came factory rigged with twin Mercury OptiMax 135-HP engines mounted one-hole up. The last set of propellers were Mercury four-bladed OFFSHORE models 14.25 x 19-pitch. The top boat speed was 44-MPH at and engine speed of 5,400-RPM. The boat has a factory hardtop so the total hull weight is about 4,000-lbs. Out here on the West coast, speed is hardly ever a priority. My goal is for stern lift and good grip at low cruising speed. I've looked at some of Yamaha's published performance data. Based on those reports, I'm inclined to think a 14.25 x 17-pitch would be ideal. I'm thinking Power Tech PTZ or PTC series.
Last edited by ivansfo on Thu Oct 14, 2021 7:43 pm, edited 1 time in total.

conch
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Re: 23 Conquest repowered with twin Yamaha F150s

Postby conch » Thu Oct 14, 2021 1:27 pm

You have made a nice re-power.

I suggest using Mercury REVOLUTION4 17-pitch. They should give stern lift.

I like the Rubex hubs to quiet the shifting sounds.

Visit Propgods.com for excellent propeller information and a website to ask questions. Propgods ships propellers for testing through the mail for a reasonable fee, so the buyer can make-up his mind.

I didn't notice the hull year, but 4000-lbs rigged with fuel sounds light [for a 23 CONQUEST with twin four-stroke-power-cycle engines].

ivansfo
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Re: 23 Conquest repowered with twin Yamaha F150s

Postby ivansfo » Thu Oct 14, 2021 6:06 pm

Conch-- I heard of Propgods long ago but wasn't aware they were still around. I'm checking out their forum now and there's a wealth of info there. Thanks for the tip.

Regarding the REVOLUTION4 propeller, I actually bought one long ago to try with my Mercury 135-HP engines. Out of the box that prop was big and heavy. So much so that I never bothered testing it on that 135 mid-size Merc. The F150s seems to be in the same class as the Merc 135.

You don't think the REVOLUTION4 is too much prop for this gear case?

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Fri Oct 15, 2021 8:36 am

If the boat hit 44-MPH with twin 135-HP engines, then it certainly should achieve that same speed with twin F150 engines. On that basis I would use 44-MPH or maybe 45-MPH as a target for top boat speed. If you give the information about the F150 requested above, then a trial pitch can be calculated based on the notion of hitting 45-MPH with a SLIP of 10. But without gear ratio and engine speed range, calculating a pitch is impossible.

The REVOLUTION4 is a very big, very heavy, very hard to turn propeller. I would not consider that a 17-pitch REVOLUTION4 would be the same engine load as a typical three-blade 17-pitch propeller, and UNDER NO CIRCUMSTANCE would I think that a 17-pitch REVOLUTION4 would be the equivalent to an aluminum three-blade 17-pitch test propeller.

The RUBEX rubber hub kit is a good replacement for the FLO-TORQ II Mercury hub kit.

The suggestion to get advice from Ken Reeves at PROPGODS is good advice, but that should not foreclose further discussion here. Also, you better verify with your dealer that his offer to provide test propellers will still be good if you decide to buy the final propellers from PROPGODS.

The Yamaha OEM propellers are generally very good propellers. They bought PRECISION PROPELLER, and the Yamaha-branded propellers are made in the USA by Precision Propellers at their Indianapolis facility. More at

https://yamaha-indianapolis.com

I would expect the Yamaha dealer to be more inclined to sell Yamaha propellers for a new Yamaha engine.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Fri Oct 15, 2021 8:50 am

As seen above in Figure 1, the new engines are mounted in the lowest possible position on the transom of the 23 CONQUEST. The engine mounting height is an important factor in performance and propeller testing. You may want to closely observe the location of the anti-ventilation plates of the twin engines relative to the flow of water around the gear case when you get the boat underway with the test propellers. Raising the engine mounting height may be something you and the dealer should discuss.

Also, the weight of twin four-stroke-power-cycle F150 engines on the transom is like to affect the static trim on the boat, particularly on a 23-footer. You may want to consider reducing weight in the stern of the boat to compensate for the increase in engine weight.

conch
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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby conch » Fri Oct 15, 2021 10:52 am

Did you keep the REVOLUTION4 propellers you previously purchased?

What size were those REVOLUTION4 propellers?

The new engine with a gear ratio of 2:1 will spin the REVOLUTION4 just fine.

[The engine mounting should be] at least two-holes-up to begin [testing propellers].

Do your old four-bladed propellers have replaceable hub? If so try them first.

Many people are surprised to see their old propellers [used with a two-stroke-power-cycle engine] work well, even on a [four stroke-power-cycle engine of greater] horsepower. For example, as a starting point for testing, propellers used on a Yamaha 250-HP two-stoke-power-cycle engine work well on a Yamaha F300 engine.

The Yamaha F150 engines weigh about 50-lbs more than the OptiMax 135-HP engine, and the gear ratio is the same.

Try [to select a propeller that will allow the new engines to accelerate to] 6,000-RPM at full throttle.

I think [the maximum boat speed of the 23 CONQUEST with twin F150 engines will be in the range of] see 45 to 48-MPH, once you have [everything related to performance] dialed-in.

The hardtop and canvas will hold back [the top boat speed] some.

[I predict] you will really enjoy the 23 CONQUEST and twin F150 combination.

ASIDES: [What type of remote controls did you buy,] mechanical or electrical?

What gauges will you use.

Have fun getting [the boat performance] just right.
Chuck
Last edited by conch on Fri Oct 15, 2021 1:11 pm, edited 1 time in total.

ivansfo
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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby ivansfo » Fri Oct 15, 2021 2:04 pm

Chuck and Jim.

The REVOLUTION4 propellers I once had for the Mercury OptiMax engines are long gone. I resold them right away after seeing how massive they were.

The last set of Mercury four-bladed propellers were sold with the old engines. In hindsight, I should have hung onto old propellers, but at that time of the sale of the old engine, it felt petty for me to not to include them.

The F150 gear ratio is 2:1.

The engines are mounted at the lowest position. This locates A-V plate right at even with the hull or 0.5-inch below the hull. I should have consulted the dealer about this before the installation, but this was one thing I forgot to bring up. I'll just test them as-is now and see how they run.

23ConquestF150-3a.jpg
Fig. 3. Close-up on engine mounting showing lowest possible position, as explained in the text.
23ConquestF150-3a.jpg (28.48 KiB) Viewed 31201 times


Engines are the DEC models that use electrical throttle and shift; the gauge is a 6Y9 digital gauge.

The port engine is counter-rotating (LH).
Last edited by ivansfo on Fri Oct 15, 2021 3:05 pm, edited 2 times in total.

jimh
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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Fri Oct 15, 2021 2:27 pm

Regarding propeller pitch estimates: for a 17-pitch propeller with a SLIP of 10 to hit 45-MPH while being turned by an engine with a 2:1 gear ratio, the engine speed will need to be greater than 6,200-RPM. You can use my PROPELLER CALCULATOR to work out other solutions. For example, at 6,000-RPM the boat speed would be about 43.5-MPH with 17-pitch and SLIP =10.

Very good on the counter-rotating engine. You have to be careful about propeller model and pitch selection; not every model and pitch is made in a LH matching pair.

ivansfo
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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby ivansfo » Fri Oct 15, 2021 2:29 pm

The Mercury OptiMax 150-HP engines were mounted one-hole-up by Boston Whaler. They ran well at this position but in rare cases, I felt the props would ventilate prematurely.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Fri Oct 15, 2021 2:42 pm

If 6,000-RPM is the recommended engine speed limit for full throttle operation, you won't get to 45-MPH with a 17-pitch unless the pitch is very understated so the SLIP calculates to about 6 or 7.

Any value of SLIP is only deduced by calculation from measurement of the other four values in the relationship. But a reasonable value to assume for a properly set-up propeller is about 10.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Fri Oct 15, 2021 2:47 pm

Re the counter-rotating engine: if seems like often the counter-rotating gear case does not run as well as the standard rotation, and the engine can't turn the same speed at full-throttle as the other standard rotation engine can.

I think the dealer's and your plan to test with 17-pitch three-blade aluminum propellers is reasonable, but at full-power the results won't be as good as with a steel propeller. The steel will have less blade distortion and have thinner blades. The top speed will be lower. Calculate a value for SLIP and it will be high with an aluminum propeller on a 150-HP engine.

ASIDE: the only person at PROPGODS is Ken. Initially there was a partner, but he is no longer there. By the way, on his own boat Ken uses a three-blade MIRAGEplus with a RUBEX hub. I know everyone is enthralled with more modern and exotic propellers, with four-blades, but for overall boating using, it is hard to beat a good three-blade propeller like the MIRAGEplus.

conch
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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby conch » Fri Oct 15, 2021 2:58 pm

I think the engines will surely need to be raised.

ASIDE ON SEVERAL OTHER NON-PERFORMANCE RELATED TOPICS

DEC electrical controls with the 6Y9 gauge is the best combination and takes the least dash space. The 6Y9 came in several versions, I assume yours is new and not used. Carefully check the fuel settings setup page for the gauge as I believe you must start the entry sequence with an empty tank.

I use a vented engine cover to keep the Latitude 24-degrees sun off the engine. I operate the engines the cover on and there has been no Ultra-violet fade on the cowling.

I believe you need to have the 6Y9 gauge connected to GPS for some of the features to work or be their most accurate version. The time and a small satellite icon will appear in the upper right header. Then auto dimming will also work when connected.

Have your dealer or yourself install the water pressure senders on the engine block which will display pressure on the 6Y9 for you.

Have your dealer or yourself install Yamaha [battery] isolator cables. They can connect to the start battery for now if you do not have a house batteries setup yet and just move them over later.

GARMIN and a few other brands of GPS plotters do not transmit the PGN system time 126992 over NMEA2000 so to get that info into your 6Y9 gauge you will either need a stand alone GPS receiver like the 19x to put the PGN on the backbone or use the 0183 connections from your plotter directly into the gauge. Sounds worse than it is to hook up but you need this info for some of the fuel consumption calculations.
Finally switch speed input over to GPS from water pressure sender under the cowling.

Owners manual and shop manual will always help.
Chuck

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Fri Oct 15, 2021 3:54 pm

I am looking forward to the results of your first propeller test with the aluminum 17-pitch propellers.

When you perform the propeller test, I suspect the boat speed at full throttle will reflect a high value of SLIP due to the aluminum propeller blades deforming a bit under the load of transmitting 150-HP to the thrust of water astern.

When reporting propeller test results, you should include data about the boat that affect the weight, such as fuel on board, persons on board, and any other gear on board. Also note if there is any additional canvas deployed that can create wind resistance.

Also note the air temperature, air humidity, water temperature, and water salinity, that is, freshwater or saltwater. All of these influences affect engine power and propeller efficiency.

Note the reported engine speed in RPM, which should be very accurate if you have OEM digital tachometer gauges. Report the boat speed, and if determined by GNSS, the speed will only be SPEED OVER GROUND. For interpretation, mentions any current in the water and the direction of wind and waves.

Give the specific data about the engine, such as model, year, variant, and so on, and similar details about the propeller, including brand, model, diameter, pitch, number of blades, and material.

If the propeller needs a hub kit, mention the brand and model of hub kit used.

ivansfo
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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby ivansfo » Sun Oct 17, 2021 1:26 am

Chuck, your tips on the 6Y9 gauge are timely. The 6Y9 I purchased was old stock the dealer had in inventory for a while. I did not plan for this gauge but was offered a good deal on it so why not.

When I ran the engines for the first time, the 6Y9 gauge showed oil pressure and voltage but not water pressure. For the cost of these motors, I expected a feature like this to be standard equipment like they were on my original Mercury engines. I just order water pressure sensors, and I will get them installed myself.

I will eventually connect the 6Y9 gauge to NMEA-0183 and the fuel sender. The harness needed for the connection was not available and I'm told are coming from Yamaha very soon.

The boat is rigged with two starting batteries and no house battery. I guess I can just leave the connection as-is now.

Jim, I'm anxious to get the performance data, too. Since the engines are new I think it will prudent to do the ten-hour break-in before running the performance tests. I hope to get this done in the next several weeks.

ivansfo
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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby ivansfo » Sun Nov 28, 2021 1:41 am

Over the past weeks I installed the water pressure sensors, put 9 hours of them, and finally got out to test the motor/propellers. I'm pleased that the motors ran well as expected. I plan to discuss this data with my dealer to order the final set of stainless props.

[Moderator's note: I hate pictures of text and numbers, so I have transcribed all the performance data from the picture seen below back to text and data.]

PERFORMANCE DATA

BOAT
Boston Whaler 23 CONQUEST
Length 23-feet
Beam 8-feet 6-inches
Dry weight 3,650-lbs
Maximum rated HP = 300
Fuel capacity = 129-gallons
Weight as tested = 5,250-lbs estimated

ENGINES
Twin Yamaha F150XCA and LF150XCA
Weight 487-lbs
Displacement 2.8-liters
Gear ratio 2:1
Recommended full-throttle RPM = 5,000 to 6,000
Mounting height: lowest possible position

PROPELLER
Yamaha three-blade painted aluminum
14-1/2 x 17-pitch

TEST CONDITIONS
Date November 25, 2021
Crew 2 persons
Elevation sea level
Wind speed less than 5-MPH
Water current less than 2-MPH

TEST RESULTS
(SOG from GPS in statute MPH)

RPM SOG GPH MPG
1000 5.3 1.5 3.5
1500 8.0 2.8 2.8
2000 8.7 4.8 1.9
2500 12.0 6.6 1.8
3000 18.0 7.7 2.4
3500 27.1 10.3 2.6
4100 33.3 14.4 2.4
4500 36.0 17.4 2.1
5000 40.0 22.7 1.7
5500 44.0 29.6 1.5
6000 49.2 31.2 1.4 (wide open throttle)

[Corrected data per update below.]


ASIDE: I took a sample Yamaha performance bulletin and over-wrote it with my data. [But since that picture contained errors in the data it was deleted--Moderator]

jimh
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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Wed Dec 01, 2021 11:26 am

Thank you for the follow-up with data from your propeller testing. The fuel economy of 2.6-MPG at a boat speed of 27.1-MPH is very good for a twin-engine powered boat.

If you purchase equivalent steel propellers and re-test, to see the change in performance will be interesting.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby Phil T » Wed Dec 01, 2021 12:29 pm

After spending a large chunk of money, I would not pitter-patter with aluminum propellers.

I would raise those engines at least two-holes and test as-is. I bet you see a performance gain of 300 to 450-RPM.

For the heavy weighted hulls, I would investigate the REVOLUTION4 propellers or comparables.

I second working with Ken Reeves.
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conch
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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby conch » Sun Dec 05, 2021 8:44 am

[The boat speed obtained in the test using the three-bladed 17-pitch aluminum Yamaha propellers] looks really good.

[A top boat speed of] maybe 51 to 53-MPH [might be obtained] once [the engine and propellers are] dialed-in and some fuel is added.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Sun Dec 05, 2021 10:33 am

conch wrote:[A top boat speed of] maybe 51 to 53-MPH [might be obtained] once... some fuel is added.
How would adding more weight in the form of more fuel result in an increase in boat speed?

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby conch » Sun Dec 05, 2021 11:52 am

For a boat with gear and people normally carried, a good indication that the propeller and engine are dialed-in is for the engine to accelerate to [close to the particular engine's maximum allowed engine speed] at full throttle.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Tue Dec 07, 2021 11:01 am

The notion (implied above) that an engine will produce its maximum power output only when it reaches its maximum engine speed is not a universal paradigm. In many outboard engines using four-stroke-power-cycle design, there may be a very strong correlation between maximum power output and maximum engine speed permitted. However, not all engine have that relationship. In many cases the manufacturer will recommend the engine speed range at which the engine actually produces its maximum power output. In selecting propellers, a good rule to use is to adhere to the manufacturer's recommended engine speed range for maximum power output--if the manufacturer gives that information or publishes a graph showing engine power as a function of engine speed.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby ivansfo » Tue Dec 07, 2021 2:10 pm

The dealer just gave me a pair of PowerTech stainless steel four-blade OFS4 propellers in 15.25 x 15-pitch. They are heavy and their weight seems comparable to a REVOLUTION4 propeller. I anticipate being able to run a sea trail within two weeks

I am fairly satisfied with the performance of the Yamaha three-blade aluminum propellers now on the engine. However, when shifting in or out of gear there is a loud CLUNK.

I want to raise the engine mounting height to be one-hole up or two-hols up.

While propeller testing, I will leave the engine mounting as it is now, at the lowest-possible-position, in order to not make engine mounting height a new variable among the propellers tested.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Wed Dec 08, 2021 10:07 am

ivansfo wrote:I am fairly satisfied with the performance of the Yamaha three-blade aluminum propellers now on the engine. However, when shifting in or out of gear there is a loud CLUNK.
If aluminum three-blue propellers cause a CLUNK from the gear case when shifting, then using four-blade stainless steel heavy propeller (about the weight of a REVOLUTION4) is probably going to cause the CLUCK to become more prominent.

ivansfo wrote:The dealer just gave me a pair of PowerTech stainless steel four-blade OFS4 propellers in 15.25 x 15-pitch.
What sort of hubs are used on these OFS4 propellers?

Are the hubs pressed-in-rubber?

Are the hubs a plastic universal-fit type hub?

Propeller rattle and loud CLUNK when shifting are problems with larger, heavier, multi-blade propellers. Often some sort of resilient hub kit design is used to reduce propeller rattle and CLUNK with them.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Wed Dec 08, 2021 10:22 am

I have calculated the value for SLIP using your performance data:


TEST RESULTS
(SOG from GPS in statute MPH)

RPM SOG SLIP
3500 27.1 3.8
4100 33.3 -0.9
4500 36.0 0.6
5000 40.0 0.6
5500 44.0 0.6
6000 49.2 -1.9
[Recalculated SLIP based on the corrected data.--jimh]

The SLIP values are not reasonable. A negative value for SLIP indicates the propeller is advancing faster than its pitch allows, which typically means the propeller pitch is understated. Values of SLIP less than 1.0 are also very unusual. These anomalies indicate some problem with the data or with the propeller pitch.

Are you certain the propeller pitch was marked as 17-pitch?

Lower SLIP values may occur with twin engines, but these values seem too low or too negative. Or perhaps the test was done with a favorable current in the water adding several MPH to the boat speed over ground.

Regarding propeller testing, conducting the tests for each propeller as closely as possible to the other propellers also helps to reduce the effect of environmental variables such as air temperature, air humidity, water temperature, wind, and current. Testing done the same day in matter of hours is probably the best way to reduce the influence of environmental effects.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby ivansfo » Fri Dec 10, 2021 5:35 pm

Early this week I calculated negative slip too which I could not figure out why. I just looked over my data and notice the 4000rpm was actually 4100rpm. MPH and RPM at WOT are accurate.

The location of the test was South San Francisco Bay where there isn't a lot of current. We were in the shallows so current should be no more than 1mph. Winds were very clam. In my opinion, conditions were pretty ideal for the test.

diameterPitch.jpg
Fig. 5. The Yamaha aluminum three-blade propellers are marked 14-1/2 x 17-pitch.
diameterPitch.jpg (9.77 KiB) Viewed 30023 times


bladeCup.jpg
Fig. 6. There seems to be a little [blade] cupping.
bladeCup.jpg (21.15 KiB) Viewed 30023 times

Blade cupping might be a contributing factor to the propeller's effective pitch.

The propeller Yamaha part numbers are 6G5-45947-01 and 6K1-45947-00.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby ivansfo » Fri Dec 10, 2021 5:37 pm

For the aluminum propellers tested earlier, at 5960-RPM boat speed was 49.2-MPH, and a new correct value for 4141-RPM boat speed was 33.3-MPH.
seaStateOnSFBay.jpg
Fig. 7. Wave height during test.
seaStateOnSFBay.jpg (24.75 KiB) Viewed 30026 times

ivansfo
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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby ivansfo » Sun Dec 19, 2021 2:24 pm

I have completed another round of propeller testing on San Francisco Bay. The propellers tested were a set of PowerTech OFS4 four-blade stainless steel propellers 15.25 x 15-pitch. Taking these propellers out of the box they felt heavy; I weight the propellers with the added Cushion Lok hubs on a bathroom scale: 16.4-lbs per propeller.

The OFS4 propellers did not work out well on my 23 CONQUEST boat. With a 15-pitch the Yamaha F150 engines speed seemed like the boat was under-propped. At a top boat speed of about 45-MPH, the engines were (likely) hitting their rev-limiters at 6,100-RPM.

There was a vibration coming from the engines which could be felt at the helm when running at speeds greater than 1,500-RPM. I do not know the reason for the vibration but it almost felt like the propellers were not balanced.

There was no CLUNK shifting in-and-out of gear with these propellers. I believe this is due to the impact absorbing Cushion Loc Hub fitted on this set of propellers.

I did not feel these propellers were good for my setup so they were boxed up and sent back to my dealer. Decided I will just buy the Yamaha tree-blade aluminum from my dealer and just run them for the time being. I'll revisit upgrading to stainless propellers next spring when there are more boating opportunities.

An interesting note. Yesterday I received a phone call from my dealer that one of the OFS4 propellers was actually a 14-pitch instead of 15-pitch. Apparently PowerTech put the wrong propeller in the box. So the performance data collected here with the OFS4 is flawed.


PERFORMANCE DATA

BOAT
Boston Whaler 23 CONQUEST
Length 23-feet
Beam 8-feet 6-inches
Dry weight 3,650-lbs
Maximum rated HP = 300
Fuel capacity = 129-gallons
Weight as tested = 5,250-lbs estimated

ENGINES
Twin Yamaha F150XCA and LF150XCA
Weight 487-lbs
Displacement 2.8-liters
Gear ratio 2:1
Recommended full-throttle RPM = 5,000 to 6,000
Mounting height: lowest possible position

PROPELLER
Powertech OFS4 Stainless Steel 4-Blade
(1) 15-1/4 x 15-pitch
(1) 15-1/4 x 14-pitch


TEST CONDITIONS
Date Dec 10, 2021
Crew 1 persons
Elevation sea level
Wind speed less than 5-MPH
Water current less than 2-MPH

TEST RESULTS
(SOG from GPS in statute MPH)

RPM    MPH   GPH   MPG
1000 5.3 1.5 3.6
1500 7.6 2.7 2.8
2000 9.3 4.7 2.0
2500 12.6 6.5 1.9
3000 20.6 8.2 2.6
3500 25.6 10.3 2.5
4000 30.6 12.8 2.4
4500 33.5 15.7 2.1
5000 37.0 19.8 1.9
5500 40.5 25.1 1.6
6100 44.8 30.0 1.4 (WOT)


powerTechOSF4.jpg
Fig. 8. PowerTech OSF4 propellers installed for testing.
powerTechOSF4.jpg (27.27 KiB) Viewed 30027 times

jimh
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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Mon Dec 20, 2021 7:55 am

Your measurement of the weight of the propellers at over 16-lbs is interesting. I have never weighed any of the propellers I have used. I will have to include that in my evaluation process.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Mon Dec 20, 2021 8:08 am

Your positive comments about the PowerTech Cushion Lok hub made me curious about its design and installation. I found this interesting short presentation demonstrating how a Cushion Lok hub for a PowerTech propeller is installed or removed:

https://www.youtube.com/watch?v=PDrVPRwCa2M

From watching the presentation, my inference is the Cushion Lok hub must be unique in its design and is useful only on certain PowerTech propellers. The design of the propeller hub seems to be quite different from the more-square and tapering aperture seen on the Mercury Flo-Torq propellers and several other brands with a field-replacement hub design. A special tool also appears to be be necessary to drive the hub into or out of the propeller aperture.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Mon Dec 20, 2021 8:26 am

The creation of vibrations in the engines with different propellers is often related to the number of propeller blades.

During rotation of the propeller, a propeller blade becomes aligned with the gear case, so the propeller is moving in water that is in the shadow of the gear case. For propellers with three-blades (or five-blades), the alignment of an individual blade occurs twice, once on the upper half of rotation and again on the bottom half of rotation. With an even number of blades--four-blades for example--the shadowing of blade occurs in pairs, with one blade on the upper and a opposing blade on the lower aligning with the gear case.

When the blades are shadowed by the gear case, the water flow is different than in other parts of the arc, and this is inferred to generate some slight change in propeller loading onto the engine, which in turn is likely to cause a vibration.

With a three-blade propeller there are six occurrences per revolution for a blade to be in shadow. With a four-blade propeller, there are only two occurrences per revolution, but the effect may be greater because two blades are simultaneously in shadow. Or perhaps the effect is minimized because the direction of the blade relative to the gear case shadow are in opposite directions and may tend to cancel vibration

The frequency of the vibration is related to the shaft speed, not the engine speed. So the effect varies depending on the gear reduction used in the engine. For example:

Assume the gear ratio of an an engine is 2:1. At an engine speed of 1,500-RPM the shaft speed is then 750-RPM. Converting this to revolutions-per-second (divide by 60) give a shaft speed of 12.5-Hertz. If the three-blade propeller generates six vibration-inducing pulses from blade-shadowing per revolution, then the fundamental vibration frequency would be 75-Hz. If a four-blade propeller is used, it produces only two vibration-inducing pulses per revolution, and the fundamental frequency moves down to 25-Hz.

With twin engines the effects become harder to predict, because the phase of the propeller shaft rotation is not synchronized, so the vibration-inducing effects of the propeller blades becomes randomly aligned.

How the change in vibration of the engines is coupled to the boat also depends on the design of the engine mounts and the stiffness of the engine mount cushioning elements--and on the stiffness of the transom on the boat.

In testing three-blade and four-blade propellers on my boat, I have observed that the frequency and strength of a vibration induced into the boat seems to change with the number of propeller blades. However, in my observation, the four-blade propeller tended to result in less vibration. My inference is the frequency of the vibration-inducing pulses from the propeller being much lower moved the excitation pulses to a frequency below the resonance of anything in the boat that wanted to vibrate.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Mon Dec 20, 2021 9:28 am

ivansfo wrote:...I received a phone call from my dealer that one of the OFS4 propellers was actually a 14-pitch instead of 15-pitch.
I presume the propeller pitch was correctly marked on the propeller, and the propeller just wound up in a box with the wrong markings.

Referring to the Yamaha aluminum three-blade propellers:
ivansfo wrote:There seems to be a little cupping
If there is blade cupping, it is very difficult to see any blade cup illustrated in Fig. 6.

ivansfo wrote:Blade cupping might be a contributing factor to the propeller's effective pitch.
Blade cupping always tends to increase the propeller's effective pitch.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Mon Dec 20, 2021 9:39 am

Regarding engine vibration: because the engines are four-cylinder in-line engines they may be more prone to vibration. An in-line four-cylinder design is not an inherently balanced engine, and they are generally used with balancing shafts to counteract vibration, Also, with four-stroke-power-cycle engines the power stroke occurs only half as often as compared with two-stroke engines, resulting in the vibration being lower frequency.

Perhaps the four-cylinder in-line configuration, the four-stroke-power-cycle design, and the four-blade propeller all aligned at a low frequency to produce the vibration you noted in testing the PowerTech OSF4 propellers.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby ivansfo » Wed Dec 22, 2021 12:11 am

The shadow effect of the gear case on propeller blades is something I never heard or read about. Thanks for the detailed explanation of that effect.

These F150 engine are still very new to me; I'm still getting acquainted with how they run. The vibration with the OFS4 stainless steel four-blade propellers was something I did not notice while running the Yamaha three-blade aluminum propellers. This led me to think it's perhaps due the diameter of the OFS4. The blades on the 15.25-inch-diameter OFS4 prop come within 0.5-inch of the [anti-ventilation] plate. I'm wondering if it's due to water turbulence and pulsation between the blade tip and the [anti-ventilation] plate.

The OFS4 propellers are back with the dealer. I'm told the 14=pitch propeller was marked correctly but just put in the wrong box by PowerTech.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Wed Dec 22, 2021 9:04 am

ivansfo wrote:The blades on the 15.25-inch-diameter OFS4 prop come within 0.5-inch of the [anti-ventilation] plate. I'm wondering if [the vibration is] due to water turbulence and pulsation between the blade tip and the [anti-ventilation] plate.


The close clearance of the anti-ventilation plate to the propeller blade tips might have some tendency to affect the vibrations created. But many people run propellers with less than 0.5-inch clearance between the blade tips and the anti-ventilation plate. I think my current set-up gives about 0.325-inch clearance, and I don't notice any unusual vibration.

Many years ago I tested a propeller with 15.75-inch diameter, which resulted in a very narrow clearance between the propeller blade tip and the anti-ventilation plate, about 0.125-inch or less. The blade tips aligned with the zinc sacrificial anode on the bottom of the anti-ventilation plate. After running the propeller for one day, I noticed a groove was being cut into the zinc anode where the blade tips were at minimum clearance. It was not from play in the propeller shaft, but most likely from the cavitation coming off the blade tips. I concluded that perhaps that propeller had too much diameter for my application.

I believe there is trend now in outboard engine gear case design for higher-horsepower engines to make the propeller aperture larger so that propellers of 16-inch diameter (or even larger) can be turned safely.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Wed Dec 22, 2021 1:06 pm

In your selection of a set of propellers for twin engine propulsion, you should consider the ability of the boat to be accelerated onto plane with only one engine. If the propellers are selected only to optimize the performance of the boat with both engines running at their full power output, there is a risk that if the boat has to be operated with only one propulsion engine working the boat may not be able to reach plane.

There is an old rule that if a boat has a single engine and is converted to have twin engines of that same power rating, then the propeller pitch would be increased by 4-inches from the single-engine pitch to account for a doubling of the power. Conversely, one could infer that if the boat were set-up with twin engines and in an unusual circumstance had to be operated with only one engine, the remaining working engine would need its propeller to be changed to one with 4-inches less pitch.

The validity of the assumption of a need to change propellers when using single engine depends on a two further assumptions: the boat was not powered above its rating with the twin engines, and the minimum power to plane is more than the power of one engine.

If the boat is powered by twin engines that combined exceed the boat's maximum power rating, then the chance that under one engine the boat can still reach plane is improved.

Check the Boston Whaler specifications for the minimum power needed to get the 23 CONQUEST boat on plane. If the specifications call for 150-HP, then you probably will need to change propellers to get the boat on plane on one 150-HP engine because the propeller pitch on that one engine will be too much to permit the engine to accelerate to its rated power output engine speed. However, if the minimum power to plane is lower, say 100-HP, then a single 150-HP might still be able to get the boat onto plane even with a propeller whose pitch was selected for twin engines.

Another choice might be to intentionally choose propellers for the twin-engine situation that were a bit under-pitched. For example, if a 17-pitch looks like the optimum, perhaps using a 16-pitch might be just enough to let one engine get the boat on plane without changing propellers.

Some boaters with twin engines carry spare propellers of lower pitch just in case they need them for single engine operation. This approach assumes you will be able to change propellers. That might not be safe if the conditions are bad. You might have to limp back to port on one engine without changing propellers. In that case, it would be very helpful if the boat could get on plane with one engine with the original propeller that was selected for twin engine operation.

ASIDE: I recently did some propeller testing in which I changed to a 15-pitch propeller from a 17-pitch propeller. I was impressed with how easily the boat accelerated and how responsive it was to throttle input. The only deficiency was the top speed declined about 2-MPH, and the fuel economy at cruise declined by about 0.2-MPG. The engine full-throttle speed increased by 250-RPM. The engine seemed very happy to be running at this lower propeller loading.

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby ivansfo » Wed Oct 18, 2023 11:18 pm

I want to update and close out this thread. I have been focused on fishing and just getting acquainted with the new twin Yamaha F150 engines paired with Yamaha 3-bladed aluminum propellers. The 3-blade aluminum propellers run well, but I have been seeking to try the Mercury ENERTIA propeller. After over a year of searching, I finally assembled a clean pair of Mercury ENERTIA 14.5-inch x 17-pitch propellers--the identical size to the Yamaha propellers I have been using.

IMG_2638.JPG
IMG_2638.JPG (131.5 KiB) Viewed 6371 times


On October 14-15, 2023, I tested the ENERTIA propellers in San Francisco Bay. I feel the performance of the ENERTIA propeller is nearly identical to the Yamaha aluminum propellers. One notable improvment with the ENERTIA propellers is the lack of shifting clunk, which I attribute to use of the Mercury SSR dampening hub.

Testing was performed in the same manner as with the Yamaha three-bladed aluminum propellers, but this time with an extra 830-lbs of gear aboard.

I plant to keep the ENERTIA propellers on the boat to see how they perform in various ocean conditions.

BREAKDOWN OF EXTRA 830 lbs
[Extra 80 gallons of fuel = 480-lbs
Filled 25 gallon livewell = 200-lbs
Additional weight of fishing buddy = 100-lbs
Fishing gear and food = 50-lbs

PROPELLER
Mercury Enertia 3-blade X7 Alloy
14-1/2 x 17-pitch

TEST CONDITIONS
Date; Oct 15, 2023
Crew ;2 persons
Elevation; sea level
Wind speed; less than 3-MPH
Water current; less than 2-MPH

TEST RESULTS
(SOG from GPS in statute MPH)

RPM SOG GPH MPG SLIP%
1000 4.9 1.4 3.6 39.1%
1500 7.8 2.8 2.8 35.4%
2000 8.5 4.3 1.9 47.2%
2500 10.2 6.5 1.5 49.3%
3000 16.3 8.5 1.9 32.5%
3500 24.7 10.3 2.4 12.3%
4000 31.6 13.0 2.4 1.9%
4500 36.4 16.4 2.2 -0.5%
5000 41.0 21.3 1.9 -1.9%
5500 44.9 28.7 1.6 -1.4%
5900 47.4 30.7 1.5 0.2% (wide open throttle)

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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Thu Oct 19, 2023 9:58 am

Because of the added 830-lbs in the testing of the ENERTIA propellers, comparing the results of the two tests is difficult. Adding that much additional weight is certain to reduce the boat speed, and, indeed we see that in the test data:

TOP BOAT SPEED
Mercury ENERTIA = 47.4-MPH
Yamaha Aluminum = 49.2-MPH

This is essentially the opposite outcome that most would expect, that is, the ENERTIA propellers, being stainless steel, being made from Unobtainium X7 alloy, and being noted for their ability to increase top speed, should have demonstrated a boat speed increase. But the opposite outcome is explained by the extra weight. Even though a 23 CONQUEST is not a lightweight boat, adding 830-lbs is certain to have decreased the top boat speed the twin 150-HP engines could deliver.

Other influences can affect the engine power output, such as air temperature and humidity. Water temperature can also affect propeller performance. For these reasons, comparison testing should be done with as much similarity as possible.