Please give advice------Briggs and Stratton power chart

[efc1978]

Hello,
Looking to buy a lawnmower, residential backyard about 1 hour of mowing with some slightly thick parts...
I have attached 3 power charts from Briggs and Stratton website of the 3 I've narrowed it down to.
I don't know anything about engines, please give advice on the best cutting ability.
3 power charts attached for the following:
550EX / 140cc
625EX / 150cc
675EX / 190cc
Thanks for any advice.

 

[efc1978]

I forgot to say, the 625EX is the one I'm thinking of buying, how does it compare to the other 2?

 

[bertsmobile1]

Not really sure what you are driving at.
What mower are you looking to fit these engine to ?
The mower deck size & shape will affect the mowing a lot more than the torque of the engine.
Are you throwing , catching or mulching ?
Bar blade , swing back on composite bar or swing backs on disc ?
If the latter, 2 blades or 4 ?
Where are you, Tropical Queensland with 10 meters of annual rainfall or Bourke with 10 inches.
What sort of grass ? Rotaries are useless with couch or bent ?
Self propelled or plain push ?
Power curves are great for mower designers but not much good for end users.
And for governed engines, the flatter the curve the better as you can not make the engine run at peak power levels like your car.
All of them will be set to run somewhere between 3200 rpm & 3600 rpm depending upon the width of the cut.
There are laws regarding how fast blades are allowed to run so that determines the maximum governed speed of the engine in a particular mower.

Whatever you end up with, keeping the blades sharp will make a much bigger difference than the size of the engine.
The old 160cc ( 6.5Hp) Power torque runs 18" & 19" decks with no trouble in both the 2 blade throw/catch and the 4 blade mulch/catch configurations.
The same engine is also fitted to the 20 inch Self Propelled the 22" self propelled and the 24" push only and it works effortlessly in all 5 applications.
I mow down 2" diameter Privat with my 24" along with 10' tall lantanna , blackberries, Bamboo and Pampas Grass.
The motor has plenty enough power to mow down thicker scrub, but the blades won't take it and my feet are only 18" behind the spinning blades.

 

[efc1978]

Hi,
The 3 options are 18" push mowers with 4 blades, catching grass about 1" to 1.5" (some areas grow longer than others), about 1 hour job in Melbourne.
Thanks

 

[bertsmobile1]

Hi,
The 3 options are 18" push mowers with 4 blades, catching grass about 1" to 1.5" (some areas grow longer than others), about 1 hour job in Melbourne.
Thanks

1" is borderline for a rotary mower they work best at 2" or longer.
Any one of the three will be quite fine for your purposes.
You would be better to make your decision upon things like air filters ,fuel taps & ease of maintenance.
If you are a bit pressed for cash then go for the cheapest option.
If not go for the engine that has the best protection for the throttle linkages.
The throttle linkages sit out front of the carb and take a beating going under bushes , fences etc and get bent very easily then the mower will run slow.
Bent linkages account for about 75% of my B&S push mower call outs.
Being in Melbourne you will only be mowing about 8 months per year so a fuel tap is good so you can run the engine dry before changing the oil prior to storing the mower over winter.
And either plain unleaded or premium unleaded, never e10.
The slop we get down here pretending to be petrol is even worse than the slop they get fed in the states.
About 1/2 the small tool work I do is cleaning dried out fuel residues from carbs so much I have burned out my first ultrasonic cleaner which runs fairly well 10 hours /day

 

[efc1978]

Thanks for the info...
Bye the way, what approx torque would a Victa mower purchased around 1994 be?, sorry I can't even remember the actual mower model, so it might be a hard question to answer, but I guess most residential Victa's from around then were similar power.
Thanks

 

[bertsmobile1]

From memory the power torque series II came in two outputs.
A high compression which was rated at 6.25Hp and the low compression rated at 5Hp
Never seen a torque curve diagram for one as they had way more power than was needed for the application.
AFAIK the difference was all in the head the high comp one has a decompressor and the low power one does not but the castings are the same, you can see the unmachined space for the decompressor to go.
Never bothered to compare them and have no idea why they made them 2 different ways.
However you have to remember that blue smokes are all revs, so comparing the power torque to the equivalent 4 stroke is very difficult.
The 24" came with a power torque , Honda c160 or B & S and both the 4 strokes were hopeless where as on the std 18" mower deck there was little difference till you got into wet grass or mulching.
The big trouble with comparing power torques is much like trying to comparre Hondas.
Each engine ran for a very long time and often the produced 4 different identical looking engines at the same time.
A lot of the changes were quite subtle like variations in the port size & shape while the Mk I to Mk II was quite dramatic as the latter had 1/3 of the finning as the former which actually cooled too much, not bad for an alloy headed iron motor.
If you are trying to remember how yours went back then, try to remember what it was like new out of the box, not what it went like 20 years latter having never been serviced.
The big problem was they very rarely broke down so never got serviced as they slowly deteriorated and became almost impossible to start.
A $25 set of parts brings them back to almost as new provided the bore is not scored.

 

[efc1978]

Thanks for the info and opinions!
Going by the power chart what horsepower would the 625EX be equivelant to?, the website says 8.5Nm / 150cc.
Thanks again!

 

[cpurvis]

Multiply torque (in ft-lb) by rpm and divide by 5252. That gives you horsepower.

 

[efc1978]

Well that's interesting, unless I got something wrong....
If you read the fine print at the bottom of those power charts I posted from the Briggs and Stratton website, it says HP is measured at 3600 RPM, so looking at the charts I posted the 625EX 8.5Nm 150cc is a bit above 7.6Nm at 3600, and the 675EX 9.1Nm 190cc is about 7.8Nm at 3600, so when I used the converter at the below link to convert 7.6Nm and 7.8Nm at 3600 RPM to HP the 625EX is 3.84 HP and the 675EX is 3.94 HP, just 1 tenth of a % difference between the 2, according to the B&S website if I correctly understood......
WEN Technology - Calculators