1981 Motor Boating Magazine v20 with Merc 200hp

[THEFERMANATOR]

Originally Posted by Destroyer

That's a great article, and it confirms what I've thought for a long time. 200 hp is simply better. (Think of a house air conditioner.. too small a window unit and it has to run all the time. Make it bigger and it works less to deliver the same cooling.... in other words, it's more economical) The same with a 200 vs a 150 on our size boats.

At any rate. it was a good article and I thank you BigShrimpin for finding it. I just wish they mentioned what pitch prop they were using in their tests. That would have helped a lot.

The cooling analogy isn't a good one as it has been proven time and time again that a 90-95% duty cycle of an A/C unit is MORE efficient than an oversized unit that doesn't run as much. If an A/C is oversized, the unit doesn't run enough to remove the humidity, yes it runs less, but it uses more electric while running, so you end up using just as much electricity, but don't remove as much himidity leaving your home feeling cold and clammy inside. Going oversized is a common misconception though. And it should be of note that a 1981 200HP MERC is actually a 175HP MERC by todays standards.

Originally Posted by bgreene

Now imagine the benefits of 300 hp !

But seriously, a couple of things......
1. engine weight - they show the 200hp as lighter than the 175 and 150. I believe it's backwards. Also, at less than 400lbs, all three of these engines are considerably lighter than many current outboards.... my etec 200 hp is more like 525 lbs.

2. engine weight - based on the reality of current 200 hp weight, the 150 truly is lighter, and this has some advantages too........

So, for those with 150hp pushing V's....... that's a very fine choice for these boats, with over 40mph top end, and less weight on the transom.

Engine height comment - I moved one hole further than my shop rigged, and still have 1 hole higher remaining. Might try it.........or not.

The 200HP 2.4L MERC WAS lighter than the 150 of it's day. The 200HP engine was a chrome bore or nicasil block whereas the 150 was a steel sleeved engine. And without all the extra crap on outboards, they used to be pretty light. My 225 EVINRUDE only weighed in around 465 pounds or so for the big V-6. SUZUKI had a 225HP outboard with fuel injection, dual plugs, the whole shebang, and it only weighed 470 pounds.

Keep in mind these tests are with carbed 2 stroke engines where raw fuel going out the exhaust ports was common place. The 2.4L engine ALWAYS had an edge over the 2.0L engines, so these results are what I would expect to see. Modern DFI or 4 stroke engines have changed these kind of results quite a bit.

[bgreene]

Interesting info as usual from our assorted group.

I just don't want our V guys with 150 hp to start feeling bad !

My " enormous" 3.3 liter, 200hp HO Etec..........still only runs the V21 to 49+/- mph, so is no faster than the old, light mercury 200.


I bet you're correct THERM, today's DFI 150 likely more fuel efficient than 200 DFI.

[THEFERMANATOR]

DFI's equalled the field out so it brought you down closer to the 1 GPH per 11-13HP across the RPM range. The old rule of thumb for carbed 2 strokes was they would burn 1 GPH for every 10HP they put out. My 140 burned right around 13-15 GPH, my 225 was around 23-25(but it was putting out closer to 250 with porting, so right on track for the 1=10 rule). At cruise you used to go to the north side of this number, but many engines were ALOT higher. DFI's and 4 strokes maintain this balance across the RPM band pretty linearly. So if a hull takes say 120HP to run at 30MPH, a 150/175/200 will all be pretty close to 10GPH fuel burn. I know that with lean burn engines nowadays, they are doing even better than the 1=12 rule.

[bigshrimpin]

as ferm mentioned in 1981 the 200 was a vertical reed 2.4L motor without fingerports and 175 was a 2.0L with the big open exhaust. The 1981 v200 is very close to the same power of the mid 80's 175 . . . it just doesn't have fingerports. So the mid 80's 175 is actually a bit stronger if run it with a 200 exhaust tuner.

This is the combo I run on my boat and it's really really fuel efficient . . . not that we'll be thinking about that with Gas back down to $1.60

This is my cruise with a mid 80's 2.4L 175 powerhead on 200 mid section pushing 23 seacraft. Performance was almost identical with the v200 powerhead.

[THEFERMANATOR]

My 81 150 is the most fuel efficient engine I EVER ran in a large outboard. It was on a bass boat, but I could run for HOURS on a 14 gallon tank. Running along at 3600 or so it only burned 4-5 GPH which was a FAR CRY from my 2.5L XRI 150 I had on my flats boat that burned 11-12 GPH running the same speeds at teh same RPM's with the same pitch prop.

[jamesbalog]

I have an 81 2.4 200 merc on my boat now and love the thing, it replaced an 88 175 johnson. The difference in fuel economy is night and day, the 2.4 merc wins hands down

[THEFERMANATOR]

Originally Posted by jamesbalog

I have an 81 2.4 200 merc on my boat now and love the thing, it replaced an 88 175 johnson. The difference in fuel economy is night and day, the 2.4 merc wins hands down

The 88 175 JOHNSON was a cross flow fuel HOG! The old OMC cross flow engines were as reliable as ANY outboard ever built, idled good, and had gobs of bottom end power, but they could drink fuel like NOBODIES business. Still can't believe MERCURY got rid of the 2.4L engine that had good power and GREAT economy for the 2.5L that drinked fuel in the same league as the OMC cross flow engines.

[Destroyer]

Originally Posted by THEFERMANATOR

The cooling analogy isn't a good one as it has been proven time and time again that a 90-95% duty cycle of an A/C unit is MORE efficient than an oversized unit that doesn't run as much. If an A/C is oversized, the unit doesn't run enough to remove the humidity, yes it runs less, but it uses more electric while running, so you end up using just as much electricity, but don't remove as much himidity leaving your home feeling cold and clammy inside. Going oversized is a common misconception though.

I did specify a small window unit. While I agree with you on a whole house unit using more electricity that's not really the case with small window units.
In many cases the difference between a 4500btu or a 5000btu is the size of the evap coil with the compressor being the same size for both of them. The electric usage is less per btu with the larger unit while achieving the same RH decrease and cooling. And of course, a case could also be made that using several window units to cool a home will cost more than running just one large central unit to do the same thing, because the central unit will be running one compressor on 220v while the window units will be running multiple compressors at 115V. (But that's no longer comparing apples to oranges, so it's really not a good comparison).

Additionally, the compressors duty cycle is a good thing to know while sizing a unit for a particular job.. Some need to have a rest period of a certain percentage of their operating time, to give the compressor time to cool down. You want this to happen to prevent breakdowns and to prolong the life of the compressor in your A/C unit. Usually, the duty cycle is expressed as a percentage of a certain time frame, often a 10 minute segment. So a duty cycle of 50% for a particular brand and model of A/C would mean that this particular unit could run steadily for 10 minutes, and then it must have a 10 minute rest period before it kicks in to cool again. Often it's the home owner that gets caught in the duty cycle trap, not knowing what the duty cycle of their unit is, and burning it out prematurely through too prolonged a usage. The point being that any money you might save in electricity by running a higher duty cycle unit might be negatively impacted if your unit fails in X years instead of Y.

I think the same could be said for a 200hp vs a 150hp. If all you're doing is cruising along at say 30 knots wouldn't the 200 be just loafing along at a lower rpm while the 150 would need to be running at a higher rpm just to maintain the same speed? I'd think that the 200 would be more fuel efficient under those conditions. (And really, when you're out in the ocean, you hardly ever get the nice flat seas that allow you to really let it all hang out. Most times it's 30-35 if you're lucky).

[bgreene]

The equation also includes evaluation of " total cost "

Comparing 200 hp Etec G1 to 4 strokes, the 4's get considerably better fuel economy in most ranges of running.

The 4's however require more frequent and more expensive maintenance, so it becomes a matter of how many hours running to make up for the additional costs.

The Etec G2 fuel economy jumps another 10-20% closing that gap.

So for use on a V, I'd say the ultimate fuel economy would come from a 150hp 4 stroke, providing a cruising range well over 300 miles on 60 gallon tank.

[THEFERMANATOR]

Originally Posted by Destroyer

I did specify a small window unit. While I agree with you on a whole house unit using more electricity that's not really the case with small window units.
In many cases the difference between a 4500btu or a 5000btu is the size of the evap coil with the compressor being the same size for both of them. The electric usage is less per btu with the larger unit while achieving the same RH decrease and cooling. And of course, a case could also be made that using several window units to cool a home will cost more than running just one large central unit to do the same thing, because the central unit will be running one compressor on 220v while the window units will be running multiple compressors at 115V. (But that's no longer comparing apples to oranges, so it's really not a good comparison).

Additionally, the compressors duty cycle is a good thing to know while sizing a unit for a particular job.. Some need to have a rest period of a certain percentage of their operating time, to give the compressor time to cool down. You want this to happen to prevent breakdowns and to prolong the life of the compressor in your A/C unit. Usually, the duty cycle is expressed as a percentage of a certain time frame, often a 10 minute segment. So a duty cycle of 50% for a particular brand and model of A/C would mean that this particular unit could run steadily for 10 minutes, and then it must have a 10 minute rest period before it kicks in to cool again. Often it's the home owner that gets caught in the duty cycle trap, not knowing what the duty cycle of their unit is, and burning it out prematurely through too prolonged a usage. The point being that any money you might save in electricity by running a higher duty cycle unit might be negatively impacted if your unit fails in X years instead of Y.

I think the same could be said for a 200hp vs a 150hp. If all you're doing is cruising along at say 30 knots wouldn't the 200 be just loafing along at a lower rpm while the 150 would need to be running at a higher rpm just to maintain the same speed? I'd think that the 200 would be more fuel efficient under those conditions. (And really, when you're out in the ocean, you hardly ever get the nice flat seas that allow you to really let it all hang out. Most times it's 30-35 if you're lucky).

Most compressors get cooled by being properly charged, and having the correct charge in the system. A correctly charged system will have a compressor that is condensating at the suction line, and even on that side of the housing. The idea is to have the system charged to the point so that once the system is stabilized and the home is cooled down, there is just enough liquid making it to the compressor to cool it.

As to the 200 loafing along VS the 150 spinning up, this is only true to a small degree. It takes X amount of HP to push a vessel at Y amount of speed. And for the most part, it takes pretty close to Z amount of fuel to make X amount of HP. Where the biggest differences come in is in the engines efficiency to produce HP. The 2.4L 200HP engine was FAR more efficient than the 2.0L 150 at putting out X amount of HP. Or look at it this way. A mid 80's 150 EVINRUDE will gulp down an EASY 12 GPH cruising along at say 4400 RPM's cruising putting out say 120 HP. A 2.0L MERCURY doing the same exact RPM's puttting out the same exact amount of HP would burn probably 8-9 GPH. Now my old 140 EVINRUDE running along even at 5000 RPM's probably putting out the same 120HP would do this burning around 7-8 GPH, and it's turning more RPM's than the other 2, using less fuel than either one doing it.

Or take a MERCURY 2.5L engine. It could be had anywhere from 150-280HP, but only to 200HP for feeshing engines. Now the same basic engine(I realize they had horizontal and vertical reed engines as well as I believe some had finger ports, and some did not) with a 50HP power spread, and yet they all burned with a few GPH of each other running along at say a 4000 RPM cruise.