Would 4hp outboard push 36' monohull?

[Terra Nova]

Originally Posted by er9

...it is a viable option...

No, it isn't.

[reed1v]

Originally Posted by Terra Nova

No, it isn't.

Its a simple engineering problem. Weight to be moved, resistance factor, force applied.
"here's how to use it. Take your waterline length, 19 and find the square root of it.(calculator)
which is 4.35 and multiply it let's say by the 1.34 which = 5.84 knots, to change to m.p.h. multiply that answer by 1.15 which = 6.7 m.p.h.
The horsepower is one horse(of gas or diesel) to obtain this speed at this waterline length for every 500 lbs of weight.
So in your case your would need about a 5 horse internal combustion engine to run a 2,500 lb boat with a waterline length of 19 ft.
To change to electric figure 3 and 1/2 horse gas or diesel engine for every one horse electric, so you would only need 1&1/2 horse electric. Of course this is under ideal conditions with no wind and waves or current."

From: HP for hull speed formula [Archive] - The WoodenBoat Forum

Bottom line, ditch the 5hp motor unless dead flat calm, no currents, no wind, no nothing.

[GILow]

So ER9, was the 9.9HP a four stroke? I assume it was if it was a U.S. engine, but over here in Oz we are still allowed to buy the evil oily two stroke variety.


Matt

[buzzstar]

Originally Posted by GILow

So ER9, was the 9.9HP a four stroke? I assume it was if it was a U.S. engine, but over here in Oz we are still allowed to buy the evil oily two stroke variety. Matt

Here in the nanny (or is it ninny?) state still known as the USA (the country I love, although they keep attempting to change it to something I would have purposely avoided while younger) our "Environmental Protection" Agency without doubt adds more heat, in the form of hot air, and "greenhouse" gas (in many forms) than all of the two strokes in the world, not just those left in the USA.

[GILow]

Originally Posted by buzzstar

Here in the nanny (or is it ninny?) state still known as the USA (the country I love, although they keep attempting to change it to something I would have purposely avoided while younger) our "Environmental Protection" Agency without doubt adds more heat, in the form of hot air, and "greenhouse" gas (in many forms) than all of the two strokes in the world, not just those left in the USA.

Although I agree wholeheartedly with the sentiment here, the two stroke outboard is one of those things that does make me feel pretty uncomfortable. That distinctive oily trail I see behind them feels pretty wrong when you've just had a ten-dolphin escort down the river.

Anyway, I was mostly curious in this case because those fuel figures are indeed excellent, and I can only assume it was a four stroke donk producing them. Of course I got even better economy recently on our boat when I had to motor for three hours in glass-water conditions, but those are hardly representative figures for our boat, where I tend to budget one litre per nautical mile on average.

Matt

[buzzstar]

Originally Posted by GILow

Although I agree wholeheartedly with the sentiment here, the two stroke outboard is one of those things that does make me feel pretty uncomfortable. That distinctive oily trail I see behind them feels pretty wrong when you've just had a ten-dolphin escort down the river. Matt

Darn it, I like dolphins too. While we do not encounter river dolphins in Southern California, I agree on behalf of the ones we do encounter. I propose a trade/solution. I'd give up two stokes if the USA will give up the EPA's idiots (there probably are some rational employees who would not be given up). BTW, I realize we've already given up new two strokes, but I'd throw in the old ones too.

I live in (and was born and raised in) California where smelt are not only more common in aquariums than our inland delta region (a wonderful area for boats), but are also more important than people, and we have a state government that believes, and thus spends billions, on useless train, rather than spending anything on needed water.

Now I will shut up, because not only is this political, it is off topic.

[reed1v]

Originally Posted by GILow

So ER9, was the 9.9HP a four stroke? I assume it was if it was a U.S. engine, but over here in Oz we are still allowed to buy the evil oily two stroke variety.


Matt

Speaking of British Seagulls, Outside of losing one's hearing, tough little engines, may they rest in peace. We had several that were family heirlooms from WW2. Once in a great while still hear someone making lots of noise and know instantly that is a Seagull.

[a64pilot]

A little off topic, but as a gear head type I bemoaned the loss of leaded fuel, my beloved two smokes and the rise of God awful contraptions like computers and Catalytic converters.
But, here we are forty years later, and engines are more efficient, quiet, economical, smoother, much less emissions and have never been as powerful as they are now.
Somebody knew what they were doing, that didn't just happen

[reed1v]

Originally Posted by a64pilot

A little off topic, but as a gear head type I bemoaned the loss of leaded fuel, my beloved two smokes and the rise of God awful contraptions like computers and Catalytic converters.
But, here we are forty years later, and engines are more efficient, quiet, economical, smoother, much less emissions and have never been as powerful as they are now.
Somebody knew what they were doing, that didn't just happen

Au contraire, my cars(honda, ford, benz, etc) have always gotten around 24-28 mpg since 1960, regardless of year made, miles driven, etc. Just the prices have gone up. So they are not more efficient, not as economical since now no one can fix them, and certainly not as powerful as the old muscle cars. Maybe less emissions, but that is debatable if one includes the pollution of making them. Quieter? The old 1956 caddie made no noise when running. It was common for folks to turn the key on an already running car. Most were very quiet. Smoother ride is certainly debatable. Heavy makes its own ride.

[a64pilot]

Since 1980, US
Table 4-23: Average Fuel Efficiency of U.S. Light Duty Vehicles | Bureau of Transportation Statistics

Now interestingly I believe average fuel consumption per US household has not dropped as much, but that may be due to consumers choosing to drive SUV's and the like

I do all my own work, software and OBD II ports have made that lots easier, and the old muscle cars are wimps compared to what is available now.

I'll add cars last much longer now as well, in the 70's 100,000 miles out of a car was almost unheard of, today if you can't get a quarter millions miles out of one, you didn't maintain it.


My wife's car, a Caddy
2009 Cadillac CTS-V Sedan Compare Car 0-60 mph 3.9 | Quarter mile 12.0

What muscle car of the era ever had a sub 12 sec 1/4 mile time? I don't know of any. And that is my Wife's four door Cadillac

[a64pilot]

List of "muscle car " 1/4 mile times
DRAG TESTS 1960 - 1972

I'll be the first to admit that tire and suspension technology back then wasn't what it is today, and with modern tires and suspension they would have been much faster.
But it amazes me that my wife's Caddy will absolutely slay a 426 Hemi Road Runner, and get 20 MPG on average and be a very "civilized" car otherwise.
We live right now in THE high performance era, we just don't know it.


I apologize for the drift

[reed1v]

Originally Posted by a64pilot

List of "muscle car " 1/4 mile times
DRAG TESTS 1960 - 1972

I'll be the first to admit that tire and suspension technology back then wasn't what it is today, and with modern tires and suspension they would have been much faster.
But it amazes me that my wife's Caddy will absolutely slay a 426 Hemi Road Runner, and get 20 MPG on average and be a very "civilized" car otherwise.
We live right now in THE high performance era, we just don't know it.


I apologize for the drift

And to drift further, my wife's ancient e350 benz, about two tons of german iron, gets 30+ mpg on the open road at 75 mph. About the same as a featherlight Toy Corolla at the same speed. And that is with four wheel drive all the time. Which is about what my old 1956 Deux Chevaux got and that weighted less than my dog. The more things change....

[er9]

Originally Posted by a64pilot

You got her done, congratulations, over three hours per gallon of gas is fantastic, that is up there with Diesel efficiency, you must have found it's sweet spot.
Amazing really at how little power it takes to push a sailboat isn't it?

truly is. there actually was a point of diminishing returns. it seemed just a hair under half throttle. anything more than that and there seemed to be less and less ability to push the hull any faster. probably why i got such great gas mileage.

[er9]

Originally Posted by CC45

sweet, glad it went all ok. As an emergency motor, i would but i'll go up to a 10 0r even 15hp. Ocean can become your friend or enemy and i sure would like to get a step up for the latter. Congrats on your test. good luck on further adventures..

for me i think the sweet spot is a 10hp. powerfull enough in an emergency, small enough to hang from the rail and light enough to man handle at 87lbs.

15hp and larger start to get fairly heavy and large to manage easily i think for most sailboats.

[er9]

Originally Posted by GILow

So ER9, was the 9.9HP a four stroke? I assume it was if it was a U.S. engine, but over here in Oz we are still allowed to buy the evil oily two stroke variety.


Matt

yeah brand new mercury four stroke straight out of the box. i dont have enough experience to offer an opinion on how they compare to two strokes though from a power perspective or how prop design etc may be different.