Hi ,

I read that 4-stroke outboards are less powerful than 2-strokes, some
articles even suggest that they're only half as powerful. is this
true? from your experience, what is the hp equivalent of a, say 15 hp
4-stroke? thanks.

s o

"s o" wrote in message
oups.com...
Hi ,

I read that 4-stroke outboards are less powerful than 2-strokes, some
articles even suggest that they're only half as powerful. is this
true? from your experience, what is the hp equivalent of a, say 15 hp
4-stroke? thanks.

s o


A 15 hp 2 stroke.

s o writes:

I read that 4-stroke outboards are less powerful than 2-strokes, some
articles even suggest that they're only half as powerful.

Power *density* is much higher for 2-strokes. Less engine weight for a
given amount of power.

s o wrote:
Hi ,

I read that 4-stroke outboards are less powerful than 2-strokes, some
articles even suggest that they're only half as powerful. is this
true? from your experience, what is the hp equivalent of a, say 15 hp
4-stroke? thanks.

s o


An engines HP rating is just that, if it's placarded as 15HP or 250HP
then it will be within 10% of that, no matter it's a 2 stroke, a 4
stroke, a petrol OB or a diesel OB.

In the only "independent" tests carried out on the newer large 2 stroke
OBs they were more expensive to buy, heavier, used much more fuel & had
much less HP (the bombardier 15HP LESS) than the same HP 4 stroke OB. (A
Bombardier DFI 2 stroke, vs a Yamaha DFI 2 stroke vs a Merc 4 stroke)

If you're thinking of buying, then get a 4 stroke, everything with a
future in this EPA world is going 4 stroke.

The fact they are tried & proven technology which has revolutionised how
reliable over time OB engines can be, is just a side benefit.

K

K. Smith wrote:

also take into account an engine's given horse power is always rated at
a certian RPM .

with work, you can get 400 h.p out of a small block (350) Chevy engine.
OR you can get the same h.p out of an 855 c.i.d. Cummins. but the
reliability not to mention the torque factor is about as different as
night and day.

The modified chevy turns about 7500 RPM and the Cummins loafs at about
1800.

I suppose thats one reason you don't find any small-block chevy engines
under the hoods of Semi-trucks.

s o wrote:
Hi ,

I read that 4-stroke outboards are less powerful than 2-strokes, some
articles even suggest that they're only half as powerful. is this
true? from your experience, what is the hp equivalent of a, say 15 hp
4-stroke? thanks.

s o

15 HP is 15 HP. The difference is that that is peak HP at max rpm ... a
2 stroke will usually have more torque at lower rpm. Means: it wioll
generate more HP at a given lower rpm...

Factors like displacement play a role too and what kind you should get
depends more on what you want to do with the motor ... On a small boat
a 2 stroke is lighter and simpler.

As a kicker on a big boat you may want to use fuel from the main tank
and opt for a 4 stroke .... Also conventional 2 strokes do not like to
idle (trolling)

All is different for direct injected 2 strokes ...


Matt

s o wrote:
Hi ,

I read that 4-stroke outboards are less powerful than 2-strokes, some
articles even suggest that they're only half as powerful. is this
true? from your experience, what is the hp equivalent of a, say 15 hp
4-stroke? thanks.

s o

The major difference between a 15HP 4 stroke and a 15HP 2 stroke
is................................................ .................................................. ...............................................
2 strokes.

Unless weight is a problem, go with the 4 stroke. Two strokes are
smaller and lighter for the same HP output, but are seldom considered
more reliable than a good 4 stroke and are frequently considered less.