Outboards
Thread Starter
Burning Brakes
Joined: Mar 2003
Posts: 1,030
Likes: 0
From: Pittsburgh PA
Outboards
Just saw an ad for outboard motors-no maintenance for 3 years-not even oil changes. And that brings up something I've wondered about for years; how can outboards have such high horsepower-to displacement/weight. They have 250hp motors that weigh only a few hundred pounds. My Ls2 weighs maybe 500 lbs. It weighs more than twice as much but has less than twice the power. Can anyone shed some light on this?
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 26
From: Austin Texas
The high HP for displacement low weight Outboards are 2 cycles, no valve trains. My 60HP 4 cycle Mercury weighed over 200#'s and cost $6,000. Most of the older Mercury 2 strokes were aprx 99 cu. in. and were 150 to 175 HP(and weighed over 300#'s).
2 strokes have lots of power for their displacement since every stroke is a power stroke (no wasted exhaust stroke) but use a lot of fuel and burn a lot of oil (no oil reservoir, you add the oil to the gas and burn it up).
Old two stroke motor cycles are a good example, my 500cc Kawasaki outran everything in 1971 regardless of displacement partly because the competition was heavy 4 strokes.
2 strokes have lots of power for their displacement since every stroke is a power stroke (no wasted exhaust stroke) but use a lot of fuel and burn a lot of oil (no oil reservoir, you add the oil to the gas and burn it up).
Old two stroke motor cycles are a good example, my 500cc Kawasaki outran everything in 1971 regardless of displacement partly because the competition was heavy 4 strokes.
Burning Brakes
Joined: Nov 2005
Posts: 993
Likes: 0
From: Plano TX
Outboard motors are now emissions compliant:
"All new outboards manufactured by Mercury Marine are certified to the
United States Environmental Protection Agency, as conforming to the
requirements of the regulations for the control of air pollution from new
outboard motors."
The newest Mercury motors are about 186 cubic inch motors, make 250HP at WOT, have 2-stage, direct injection and weigh 500 lbs dry.
Yamaha has a new 5.3 V-8 outboard that makes 350 hp and weighs 800lbs
"All new outboards manufactured by Mercury Marine are certified to the
United States Environmental Protection Agency, as conforming to the
requirements of the regulations for the control of air pollution from new
outboard motors."
The newest Mercury motors are about 186 cubic inch motors, make 250HP at WOT, have 2-stage, direct injection and weigh 500 lbs dry.
Yamaha has a new 5.3 V-8 outboard that makes 350 hp and weighs 800lbs
Le Mans Master
Joined: Aug 2005
Posts: 6,709
Likes: 1
From: Pacific Northwest
St. Jude Donor '06
I had one too...but I am now toothless because it vibrated them all out along with most of the bolts in the bike...but it was GREAT fun!! 
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Team Owner
Joined: Jan 2007
Posts: 22,136
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From: In the woods looking for my thrown putter.
St. Jude Donor '13, '15
Team Owner
Joined: Feb 2000
Posts: 53,527
Likes: 77
From: Arizona
Mercury had a 300 HP OB years ago, but was slower than the 200 because it weighed so much. Not just the extra weight per se, but it upsets the Bass Boats attitude and is less efficient in the water.
90mph on the water in a 20+' Bass Boat=165+mph in the C6, in terms of sphincter clinching.
Le Mans Master
Joined: Dec 2005
Posts: 7,753
Likes: 210
From: North Western Connecticut
Boat engine usually have a huge advantage in cooling. Pull the water from the source, circulate and eject out. Pretty simple compared to the sealed cooling system cars require......
Instructor
Joined: Oct 2006
Posts: 133
Likes: 0
From: Tarpon Springs Florida
Yes, there are smog emissions requirements.
You have to remember that those published weights include midsections, lower units, cowlings, all of the electronics, etc. All of that equiptment weighs a significant amount, I would bet that the block with pistons and all only weighs about 40-50% of the published weight.
The 300 hp, Mercury Optimax XS 3.2L 6 cylinder 2-stroke direct injection block with pistons, crank, etc supposedly weighs around 250lbs.
The 300 hp Suzuki 4.0L 6 cylinder 4-stroke weighs 600 lbs fully rigged, so around 300lbs in automotive configuration.
Today's direct injection 2 strokes are also just as fuel efficient if not more so than 4 strokes, atleast in boat engines. Check out some of the tests on the new outboards, such as the 225 shoot-out in Bass and Walleye magazine a few months back, the 2 strokes were faster and more fuel efficient. They do however, burn oil.
How do you think that Optimax block would perform on the back on a dune buggy or race car? If a heavy duty radiator setup works on those buggies that run in those endurance races in the desert then I'm sure it would cool one of those things.
You have to remember that those published weights include midsections, lower units, cowlings, all of the electronics, etc. All of that equiptment weighs a significant amount, I would bet that the block with pistons and all only weighs about 40-50% of the published weight.
The 300 hp, Mercury Optimax XS 3.2L 6 cylinder 2-stroke direct injection block with pistons, crank, etc supposedly weighs around 250lbs.
The 300 hp Suzuki 4.0L 6 cylinder 4-stroke weighs 600 lbs fully rigged, so around 300lbs in automotive configuration.
Today's direct injection 2 strokes are also just as fuel efficient if not more so than 4 strokes, atleast in boat engines. Check out some of the tests on the new outboards, such as the 225 shoot-out in Bass and Walleye magazine a few months back, the 2 strokes were faster and more fuel efficient. They do however, burn oil.
How do you think that Optimax block would perform on the back on a dune buggy or race car? If a heavy duty radiator setup works on those buggies that run in those endurance races in the desert then I'm sure it would cool one of those things.
Last edited by sbennett5; Mar 25, 2007 at 11:31 PM. Reason: added info on fuel economy
Melting Slicks
Joined: Sep 2004
Posts: 3,488
Likes: 27
From: Long Island NY
You can't compare a 2-stroke to a 4-stroke. If you are, that's a big part of the discrepancy.
Team Owner
Joined: Jan 2007
Posts: 22,136
Likes: 23
From: In the woods looking for my thrown putter.
St. Jude Donor '13, '15
[QUOTE=Hoonose;1559531170
90mph on the water in a 20+' Bass Boat=165+mph in the C6, in terms of sphincter clinching.[/QUOTE]
I know this all too well. Rocking side to side with 3 inches of the boat in the water at 90+++ is a little scary. I'd rather do 165 in the vette then 90 in the boat.
By the way you guys should go to Evinrude's site and look at the new E-Tec. 2 strokes have come a LONG way.
90mph on the water in a 20+' Bass Boat=165+mph in the C6, in terms of sphincter clinching.[/QUOTE]
I know this all too well. Rocking side to side with 3 inches of the boat in the water at 90+++ is a little scary. I'd rather do 165 in the vette then 90 in the boat.
By the way you guys should go to Evinrude's site and look at the new E-Tec. 2 strokes have come a LONG way.
Last edited by Silverspeed; Mar 26, 2007 at 05:17 AM.