23 CONQUEST Twin Yamaha F150 Engines

Optimizing the performance of Boston Whaler boats
ivansfo
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Joined: Fri Nov 13, 2020 7:21 pm

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 522 times


23ConquestF150-2b.jpg
Fig. 2. View from astern.
23ConquestF150-2b.jpg (47.87 KiB) Viewed 522 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?

jimh
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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.

jimh
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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 523 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 cotter-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.

jimh
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Re: 23 CONQUEST Twin Yamaha F150 Engines

Postby jimh » Fri Oct 15, 2021 2:30 pm

The illustrating photo above shows an engine mounted one-hole-up.

jimh
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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.

jimh
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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

jimh
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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. I took a sample Yamaha performance bulletin and had some fun overwriting it.

Conquest_Report.jpg
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