New motors vs Old motors

[puddle jumper]

I was wondering if the newer outboards are more efficient with power out put than a older outboard.

A good example say my 89 force 50hp vs a 2010 merc 50hp. Both are 50hp but would the power out put be that diffrent?

 

[tx1961whaler]

Re: New motors vs Old motors

If they are both rated 50 HP at the same point (prop vs head), using the same method, then 50 HP is 50 HP. HP is the power output. Kind of like saying one 100 watt bulb consumes the same power as another 100 watt bulb. The gearcase of an outboard (solid metal gears) has not changed in the last 50 years.
However, different motors have different torque curves.

 

[Faztbullet]

Re: New motors vs Old motors

Your correct that 50 hp at prop is 50hp no matter what. The differences that do come into play are: 1)Force 50 is 2 cyl crossflow and Merc is 3 cyl looper, and a looper will burn less fuel at cruise rpm than a crossflow engine. 2) The Merc can use a larger diameter(12.5 max on std gear case/14" on Bigfoot) due to gear case design where the Force is limited to 11" thus better handling and torque.3) All this adds up to is: with the correct set up on same boat a looper will perform better whether it be a Merc/Yamaha/Johnrude.

 

[Gopher]

Re: New motors vs Old motors

I agree that every 50hp motor would supply that power at some combination of torque * rpm <http://www.engineersedge.com/motors/rotating_horsepower_equation.htm>. Efficiency at generating that torque (RPM is free, up to the thermal/mechanical limit of the design) leading to differences in fuel consumption. <http://trailerboats.com/output.cfm?id=2259109> includes consumption figures for eight 50hp motors of varying technology. New-tech is noticeably lower consumption at cruise/WOT but not enough to necessarily warrant replacement of old good-running motor. I also notice that all motors tested consistently gave best range (miles/gal) around 2/3 - 3/4 throttle.

 

[puddle jumper]

Re: New motors vs Old motors

Ya I might be able to get better performance with a newer model with a different pitch prop. Something to think about.

I am looking to up grade my out board because it,s just getting old and parts are getting harder to find. The Force has been a great motor.

Thanks for your input. Not the answer I was looking for but like you people said a 50hp is a 50 hp new or old.

 

[dingbat]

Re: New motors vs Old motors

In real life, the guys going from carbed two strokes to 4 stroke or even DFI 2 strokes are looking at 30-40% increase in fuel efficiency. At least in the High HP motors we use.

 

[pecheux]

Re: New motors vs Old motors

IMHO older motors (but much older than your 89) had more torque than newer OB's but had less overall performance.

 

[dingbat]

Re: New motors vs Old motors

IMHO older motors (but much older than your 89) had more torque than newer OB's but had less overall performance.

Torque = Horse power / RPM x 5252,. The only way to get more torque of a particalar HP would be to change the gear ratio in the lower unit. This would give you more low end torque and less top end speed.

 

[Mark_VTfisherman]

Re: New motors vs Old motors

In real life, the guys going from carbed two strokes to 4 stroke or even DFI 2 strokes are looking at 30-40% increase in fuel efficiency. At least in the High HP motors we use.

Yes, he's right! (of course even on smaller motors.

My previous 40hp 1964 Johnson would use a 6 gal tank in a 1/2 day fishing. The newer (yet still old) '85 Suzuki will go all day trolling and still have enough to get back to the ramp. Plus, with the oil injection, my oil consumption has been cut to about a third of the mix-every-tank Johnson. The new EFI/DFI has got to be fantastic compared to mid-80s carbureted motors, too. Speedwise on my trusty Niagara: old Johnson, 27-28mph, newer Suzuki, 33-34 mph GPS with the same empty boat.

Another point, the power on the newer engine - the advertised Horsepower is rated at the prop. Force, if I remember correctly, was rated the old way: at the powerhead. Reduce the label-rating on a powerhead-rated boat motor by about 15-17% to guestimate prop HP. A 50hp Force is also heavy yet performs like a strong 40hp.

Example: 2008 season my buddy switched his 1988 85hp Force to a 1989? 85hp Johnson. Both props had the same pitch. Fuel consumption went down, which was good. But most importantly, his top speed (19' boat) went from 26mph GPS to almost 34mph GPS.

puddle jumper says: "A good example say my 89 force 50hp vs a 2010 merc 50hp. Both are 50hp but would the power out put be that diffrent?"

The answer is that a 2010 2-stroke Merc/Yammi or Evinrude/whatever will be more fuel efficient at all speeds, and will also improve your top speed while still using less fuel. If the difference is as substantial as the two examples I related and you have the jingle for a new motor, the switch would be a hands-down improvement. IMHO

 

[pecheux]

Re: New motors vs Old motors

Torque = Horse power / RPM x 5252,. The only way to get more torque of a particalar HP would be to change the gear ratio in the lower unit. This would give you more low end torque and less top end speed.

Well I did not have those details in mind. But way back when (1960 or so) I owned a 10 hp Johnson and a 15 hp Evinrude seems to me these motor had much bigger blocks and I remember both these OB's could push heavier loads than the later models Johnson 9.9 hp and the 15 hp that I both owned in the mid 80's both having only 216 cc displacement. But I would rather switch than fight ... LOL