"Habbi" wrote in message
...
Is all horsepower the same?

No. There's SAE horsepower and DIN horsepower.

Would a 250 hp turbodiesel sterndrive be equal
to a 250 hp 2 stroke outboard.

No. Diesels are measured in DIN horsepower. That 250 DIN
horsepower turbodiesel will be about 400(?) SAE horsepower.
That outboard, a gas engine, is measured with a different
formula, called SAE horsepower.

It's wildly unrealistic to say that 2 stroke outboard, which
you can almost lift and hold in your arms, will do the work of
250 horses.

You can see the difference in the boating catalogues, in the
mufflers section. A certain muffler will be rated for a 25
HP diesel or a 40 HP gas engine. These engines put out the
same amount of exhaust, roughly meaning they will do the same
amount of work, which that size muffler can handle.

Obviously the OB has the weight advantage
when it come to performance but is it significant?

No, it's insignificant.

In the same boat would
the diesel carry more load/ weight before becoming lugged?

Sure. It's a lot more powerful.

I have a 31' X
12' 9 degree V aluminum workboat which I outfitted with a
250 hp johnson.
There is a similar boat 31' X 10' 13 degree V with a 230hp
volvo diesel
duoprop which outperformes me unloaded and loaded. With an
extra 1000 lbs my
boat will not plane where as the other boat will. It seems
like extra weight
affects the 2 stroke much more than the diesel. How does a
gas sterndrive
compare as well.

A 250 horsepower gas sterndrive will perform exactly the same
as your present outboard. Since it's a US gasoline engine,
that'll be 250 SAE horsepower.

Now, there's nothing wrong with any of this. This is just how
the system has grown up. The trick is, you must specify
whether it's SAE or DIN horsepower and know what the terms
mean, that's all. Then you can know how strong the engine is,
which is what you want to do.

Yanmar sells two diesel outboards, a 28 and a 32 horsepower.
Someone in here pooh-poohed them because they're heavy and
expensive. They're really _very attractive, and here we start
to see why. Yanmar sells them as workboat engines.

Joe Kovacs
SV Sea Breeze
Cooper River Marina Charleston SC

Joe,
I hate to bust your bubble, but your reply here is full of wives tales.
Please refer to this reference:
http://neptune.spacebears.com/opine/horsepwr.html You will see that for all
intent and purposes, DIN and SAE Net Horsepower are the same. I believe that
your performance comparisons and observations are due to torque curve
differences not horsepower.
Steve

"Joe Kovacs" wrote in message
...
"Habbi" wrote in message
...
Is all horsepower the same?

No. There's SAE horsepower and DIN horsepower.

Would a 250 hp turbodiesel sterndrive be equal
to a 250 hp 2 stroke outboard.

No. Diesels are measured in DIN horsepower. That 250 DIN
horsepower turbodiesel will be about 400(?) SAE horsepower.
That outboard, a gas engine, is measured with a different
formula, called SAE horsepower.

It's wildly unrealistic to say that 2 stroke outboard, which
you can almost lift and hold in your arms, will do the work of
250 horses.

You can see the difference in the boating catalogues, in the
mufflers section. A certain muffler will be rated for a 25
HP diesel or a 40 HP gas engine. These engines put out the
same amount of exhaust, roughly meaning they will do the same
amount of work, which that size muffler can handle.

Obviously the OB has the weight advantage
when it come to performance but is it significant?

No, it's insignificant.

In the same boat would
the diesel carry more load/ weight before becoming lugged?

Sure. It's a lot more powerful.

I have a 31' X
12' 9 degree V aluminum workboat which I outfitted with a
250 hp johnson.
There is a similar boat 31' X 10' 13 degree V with a 230hp
volvo diesel
duoprop which outperformes me unloaded and loaded. With an
extra 1000 lbs my
boat will not plane where as the other boat will. It seems
like extra weight
affects the 2 stroke much more than the diesel. How does a
gas sterndrive
compare as well.

A 250 horsepower gas sterndrive will perform exactly the same
as your present outboard. Since it's a US gasoline engine,
that'll be 250 SAE horsepower.

Now, there's nothing wrong with any of this. This is just how
the system has grown up. The trick is, you must specify
whether it's SAE or DIN horsepower and know what the terms
mean, that's all. Then you can know how strong the engine is,
which is what you want to do.

Yanmar sells two diesel outboards, a 28 and a 32 horsepower.
Someone in here pooh-poohed them because they're heavy and
expensive. They're really _very attractive, and here we start
to see why. Yanmar sells them as workboat engines.

Joe Kovacs
SV Sea Breeze
Cooper River Marina Charleston SC

Horsepower is horsepower is horsepower.................Steve hit it on the
money!

1 hp = 33,000 ft lb/min


There are indeed different aspects of horsepower :

Shaft Horsepower
Brake horsepower
Indicated Horsepower
Friction Horpower
etc.


Dave