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Author Topic:   Single 300-HP v. Twin 150-HP
prieye1 posted 06-24-2014 04:51 PM ET (US)   Profile for prieye1   Send Email to prieye1  
Recently purchased a 2000 Boston Whaler 23 Conquest with a Mercury 225-HP OptiMax. Is a boat of this size better off with a single 300-HP or two 150-HP's? Why do you feel the way you do ? I find the 2000 225-HP OptiMax a little loud for my liking and am considering re-powering the boat. Thanks in advance for the replies.
martyn1075 posted 06-24-2014 06:46 PM ET (US)     Profile for martyn1075  Send Email to martyn1075     
[A Boston Whaler 23 CONQUEST is] a fairly large and heavy boat to push through the water efficiently, however a modern single outboard would be my personal choice. The transom design should handle the weight and overall size of a 250 to 300-HP engine. Less maintenance, less cost, perhaps fuel burn as well. The potential of repairs, although perhaps not so high with new motors, is always a risk and headache if one is not working properly. Twins have advantages usually on long heavy boats in the larger range 25- to over 30-feet. A single on a 23 Conquest would be fine. The beam has a lot to do with how you power your boat and a 23 Conquest-- I believe--has a 8-foot 6-inch beam, considered narrow compared to a 9-foot 6-inch and wider.
Teak Oil posted 06-24-2014 08:28 PM ET (US)     Profile for Teak Oil  Send Email to Teak Oil     
Twins are a lot more money, maintenance, and burn more fuel. The only [way] would go for twins over a 300 single is if I regularly made runs offshore more than 20 miles. The water is chilly in MA so you dont wan't to be way out and in rough conditions with only a kicker to get you home.
jimh posted 06-24-2014 08:41 PM ET (US)     Profile for jimh  Send Email to jimh     
"Is the boat better off?"--that is hard to say. The boat might be marginally better with twin engines in its handling and general performance.

The real question is will you be better off with twin 150-HP engine versus a single 300-HP. The single will probably cost less to buy, to install, to operate, and to maintain than the twins. The twins will give you redundancy. The twins could be worth their added cost if you do a lot of boating offshore.

See a discussion from 2006 on precisely this topic for more opinions:

Twin 150-HP: A Thing of the Past

If cost is no object, get the twins. If cost is a consideration, decide if you can accomplish the boating you enjoy with a single engine. Considering that the boat presently has a single, I think you can make an informed judgement on that question.

contender posted 06-24-2014 09:12 PM ET (US)     Profile for contender  Send Email to contender     
Question: If you have twins and one engine does not start do you still go out?
Hoosier posted 06-24-2014 09:16 PM ET (US)     Profile for Hoosier  Send Email to Hoosier     
Here's my $0.02 contribution. I got a used 1992 23 Walkaround in 2012 that had just been repowered with twin Yamaha F-150 four strokes. Last week I took her out for a 2014 season shake down and finally got the fuel management system set up correctly (I think) and it read between 3.5 and 3.9 mpg at cruise, which for me is about 22-24 mph, for an 80 mile run around Drummond Island in Lake Huron. The speed at idle was just over 3 mph, which is a bit high for trolling, but that was with both engines running. If you have the $$ go for the twins. My "fishing boat" is a 1978 Outrage V-20 that has a single 2003 Suzuki DF-115 on it that will troll all day at 1.5-2 mph, and I've taken her across Lake Michigan twice. The single vs. twins argument is all about how you are going to use the boat, modern singles are reliable as hell, until they aren't, twins are twice as reliable, no matter what...
Hoosier posted 06-24-2014 09:21 PM ET (US)     Profile for Hoosier  Send Email to Hoosier     
Yes, because there is a parallel switch that lets you start the "bad' engine off of the "good" one once it's running. Been there, done that...
Hoosier posted 06-24-2014 09:29 PM ET (US)     Profile for Hoosier  Send Email to Hoosier     
Yes, because there is a parallel switch that lets you start the "bad' engine off of the "good" one once it's running. Been there, done that...
prieye1 posted 06-24-2014 11:36 PM ET (US)     Profile for prieye1  Send Email to prieye1     
Thanks everyone for the input.
I have decided that a single 300hp is the way to go.
jfortson posted 06-25-2014 07:12 AM ET (US)     Profile for jfortson  Send Email to jfortson     
Prieye1, Reasons for choice would be nice.
Peter posted 06-25-2014 07:59 AM ET (US)     Profile for Peter  Send Email to Peter     
Hoosier -- I would check your fuel management system calibrations because there is no way a 23 foot Whaler walk around with twin 150s should get 3.9 MPG. Your results should be similar to what is shown in this performance report. www. yamahaoutboards. com/ sites/ default/ files/ bulletins/ bulletin_4s troke_hpv6_gyt3_bulletin_otb_4strokeperf_hpv6_150hp_reg-23cc-t-f150txrc. pdf

Further, I have a 24 foot Pursuit with twin Yamaha HPDI 150s which are every bit as efficient as the F150 at cruise speed and my best cruise MPG is 2.3 MPG between 28 and 30 MPH.

Based on my results and that of the Regulator 23 report, I would expect your best cruise MPG to be in the 2 to 2.5 MPG range.

Make sure that both fuel flow sensors are sending data back to the fuel management system. If only one is sending data back then your MPG will look 2X than actual.

jimh posted 06-25-2014 08:19 PM ET (US)     Profile for jimh  Send Email to jimh     
I want to throw in with Peter on the question of Dave's boat's fuel economy. If Dave is really getting almost 4-MPG on a 23 WALKAROUND with twin 150-HP engines, I will be extremely impressed with that fuel economy. I think it's more like he's getting 2-MPG.
Teak Oil posted 06-25-2014 09:20 PM ET (US)     Profile for Teak Oil  Send Email to Teak Oil     
So far with my 300 (lighter boat though) I have seen a best of 3.76 mpg at cruise. I am sure my combined economy is well over 4 mpg as long as I keep my speed below 40 mph.

GSH posted 06-26-2014 07:11 AM ET (US)     Profile for GSH  Send Email to GSH     
On the subject of fuel economy of one big outboard versus two smaller ones:

Finnish boating magazine Kippari just some weeks ago came out with a new issue where they report on a comparison made between three boats of the same brand model and size (Nord Star 26), but set up with three different propulsion choices: diesel Volvo Penta I/O (260 HP), Mercury Verado 300 and 2 x Mercury FourStroke 150 EFI.

Disregarding the diesel alternative (being I/O, not really fair to compare as apple to apple on one parameter only with an outboard), what I was somewhat surprised by was:

The 2 x Mercury FourStroke 150 EFI clearly beats the Mercury Verado 300 on fuel economy!

This is not in line with what I consider “the conventional wisdom” of outboard performance.

As I would not go on to say that the Mercury Verado 300 must be really bad on fuel economy, I therefore would draw the conclusion that the fuel economy of the Mercury FourStroke 150 EFI most likely is very good!

Peter posted 06-26-2014 07:54 AM ET (US)     Profile for Peter  Send Email to Peter     
Throw out the conventional belief that twins are less fuel efficient than a single. The results depend on the boat.

On a 26 foot boat, which I assume that the NordStar is, the propeller surface area of the single Verado may not be sufficient to propel the boat efficiently.

Here are two performance reports from Grady White for their Freedom 255 model, one for a pair of F150s and the other for a single F300.

There is no fuel efficiency performance advantage for the single F300.

jimh posted 06-26-2014 09:17 AM ET (US)     Profile for jimh  Send Email to jimh     
In the tests that Peter points to, the single engine boat gets best MPG of 2.37-MPG and the twin engine boat gets best MPG of 2.42-MPG.

The corollary question: do twin 150-HP engines cost more than a single 300-HP?

Peter posted 06-26-2014 10:06 AM ET (US)     Profile for Peter  Send Email to Peter     
Do twins cost more? Yes. Do they cost more to maintain? Yes. Is it 2X more. No. At least with respect to fuel system maintenance you are dividing the total fuel flow into two halves. So each fuel filter in the twin 150 engine arrangement has half as much fuel flowing through it as would be the case for a single 300 and should thus last twice as long.

There is a size range, typically 23 to 25 feet, where the boat could be powered with either a large single or twins and which way to go depends a lot on the boat and the intended use.

Teak Oil posted 06-26-2014 12:42 PM ET (US)     Profile for Teak Oil  Send Email to Teak Oil     
I would be interested to see a comparison between a 22 Outrage with twin 115 E-tec's and mine, but I have not seen that combo yet, most would shy away from that combo due to weight of the twins
jimh posted 06-26-2014 12:51 PM ET (US)     Profile for jimh  Send Email to jimh     
The problem with twin 115-HP E-TEC engines as an alternative to a 300-HP single engine is:

--no counter-rotation [or maybe there is a counter--not sure on this]

--no ICON controls so no throttle synchronization

--might not get on plane with only one engine

SJUAE posted 06-26-2014 05:04 PM ET (US)     Profile for SJUAE  Send Email to SJUAE     
I just looked at the performance data on the new 220 outrage which has 5 engine options and both of the twin set-ups can hit 3 mpg but not the 3 singles options in the 3-4000 rpm range EnginePerformance/2014/323829_EnginePerf.pdf

jfortson posted 06-27-2014 09:40 AM ET (US)     Profile for jfortson  Send Email to jfortson     
I just have a casual interest in this threat, but aren't the comparisons comparing apples to oranges? It seems that the twins are 4 stroke and the singles are 2 cycle. Is if fair to compare the fuel efficiency of the different type motors.

For a true comparison, shouldn't the motor types be the same? Comparing 4 cycle to 2 cycle is a different matter than comparing singles to twins (or triples).

Peter posted 06-27-2014 01:55 PM ET (US)     Profile for Peter  Send Email to Peter     
Click on the links to the Grady-White boats. It's single versus twin 4-strokes. Apples to apples.
jimh posted 06-27-2014 02:06 PM ET (US)     Profile for jimh  Send Email to jimh     
I don't think any of the comparison data cited has involved engines of different power strokes. They're all two-stroke or four-stroke power-cycle comparisons.
Hoosier posted 06-28-2014 09:09 AM ET (US)     Profile for Hoosier  Send Email to Hoosier     
FWIW: My reported fuel economy was from my fuel management system that, I think, is centered on the much maleigned EP-85.
I was on my season startup shakedown cruise and had just reconfigured the system. The performance I reported was the GPS fuel economy as reported on the LCX-28c HD screen. I assume the "system" measures the distance traveled by GPS and then divides by fuel used as sent to it by the engine ECMs. I told it I have two engines. The beginning and ending fuel amounts were consistent with a burn of around 22+ gallons. My cruise in the22 mph range is the sweet spot for the boat/engine combnation, plus the water was flat calm with no wind. Ideal conditions. When I dropped the boat off at the DIYH shop the next day the mechanic wasn't surprised when I asked whether the performance was "for real".
Peter posted 06-28-2014 12:10 PM ET (US)     Profile for Peter  Send Email to Peter     
Ah ha. We are talking about different things. Your data is average MPG versus instant MPG. With a pair of F150s your off plane MPG will be better than your on-plane MPG which means your average MPG will be higher than your instant on-plane MPG.
jimh posted 06-28-2014 02:52 PM ET (US)     Profile for jimh  Send Email to jimh     
Hoosier posted 06-28-2014 04:21 PM ET (US)     Profile for Hoosier  Send Email to Hoosier     
I'm not sure. As I watched the display I could see the MPG change as I changed speed. It went down at high displacement speed compared to "good" planing speed. As I said, I had just gotten it reconfigured and was still wringing the bugs out, but the fuel burn for the ~80 mile trip was consistent with an average of 3.5 to 3.9 MPG.
jimh posted 06-28-2014 08:59 PM ET (US)     Profile for jimh  Send Email to jimh     
TRIP AVERAGE fuel economy is quite a different matter than instantaneous fuel economy. On my last trip, the TRIP AVERAGE was around 3.0-MPG and the typical best instantaneous fuel economy at cruise was around 2.6-MPG. On some days the average was around 3.3-MPG. There is no way to compare one boat and motor's trip average to another unless the two boats ran continually in unison, that is, always at the same speed and same amount of time at that speed.

Instantaneous fuel economy varies widely with conditions, and a following sea, a following wind, favorable wave height, good humidity and temperature will all have an influence, so on a particular leg I might see 2.5-MPG at cruise and then 2.8-MPG at that same engine speed on a different day with different conditions.

Most of the time in any sort of comparison brewed up by an engine manufacturers the fuel consumption data is carefully chosen and cooked so that the engine being favored is shown at its very best speeds and compared to another engine at its very worst speeds.

mopee3 posted 06-30-2014 08:16 PM ET (US)     Profile for mopee3  Send Email to mopee3     
[Changed topic. This new topic has now been moved to its own thread.--jimh]
deepwater posted 07-02-2014 06:02 PM ET (US)     Profile for deepwater  Send Email to deepwater     
[Changed topic. This new topic has been moved to its own thread--jimh]

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