What choice: 383 MPI or 454 Mark IV

[axelkloehn]

Hi guys,

can you give me an advice for my GT21?

I have the choice between a stock 383 MPI/321hp with 273 hours or a reworked 454 Mark IV/330hp (2 hrs.) with stainless steel risers, both for a good price (383 MPI is 1.3 the price of the 454).

They will be installed with a Bravo One Sterndrive with 1.5 ratio and 23" Mirage prop...

What's the best choice concerning fuel consumption, top-speed, torque and fun it will make? :):):)

Thanks, Axel :germany:

[The Hedgehog]

Hi guys,

can you give me an advice for my GT21?

I have the choice between a stock 383 MPI/321hp with 273 hours or a reworked 454 Mark IV/330hp (2 hrs.) with stainless steel risers, both for a good price (383 MPI is 1.3 the price of the 454).

They will be installed with a Bravo One Sterndrive with 1.5 ratio and 23" Mirage prop...

What's the best choice concerning fuel consumption, top-speed, torque and fun it will make? :):):)

Thanks, Axel :germany:

It depends on where you want to go with it. I have a 383 MAG MPI in my 18. It is a great package for the boat.

In a bigger boat and if I wanted to add some performance goodies later I would go with the 454

[axelkloehn]

It depends on where you want to go with it. I have a 383 MAG MPI in my 18. It is a great package for the boat.

In a bigger boat and if I wanted to add some performance goodies later I would go with the 454


...should go around 60 mls, not less. You' re right, a 454 has more tuning opportunities, could be a must for going 60 with a quiet heavy GT21, or?

Axel :germany:

[MOP]

...should go around 60 mls, not less. You' re right, a 454 has more tuning opportunities, could be a must for going 60 with a quiet heavy GT21, or?

Axel :germany:

Axel I have a 383 in a 22 classic, it makes about 370hp on a good day it will go 65.5mph. I think the 454 is better suited for what you want.

Phil

[BigGrizzly]

I am with Phil.

[harbormaster]

keep in mind, that though they are close to the same horsepower, the 454 because of the longer stroke, has much more needed torque

[Pismo]

keep in mind, that though they are close to the same horsepower, the 454 because of the longer stroke, has much more needed torque


The 454 has 71 more cubic inches therefore more needed torque.

[Fast Shafts]

Some thoughts on a small block:
The 383 small block engine weighs 250 lbs less than a 454 big block. What you may lack in tq, with small block, you'll loose in weight gain with a Big block. The 383 has a 3.75" stroke the 454 I think has a 4.00" stroke. The 383 can spin higher rpms than a 454.
Parts are cheaper for a small block. I'd vote small block, depending on what mods the 454 has.

[Planetwarmer]

Big Block is my vote. When I drive with a 250 lb passenger, my boat really doesn't perform noticeably different.

[HOWARD O]

Big Block is my vote. When I drive with a 250 lb passenger, my boat really doesn't perform noticeably different.

I swear I was going to say the same thing, but let it go because my sister doesn't ride in the Donzi much anyway..... :cool:

[joseph m. hahnl]

You would have to modify the transom for the Through hull exhaust if you are switching from small block to big block or Visa versa.:crossfing:

[blackhawk]

What rpm does the 383 make it's hp? Big blocks usually have more torque than small blocks but not always. If the two motors have similar hp curves then they have similar torque curves regardless of cubic inches, stroke, etc

[axelkloehn]

You would have to modify the transom for the Through hull exhaust if you are switching from small block to big block or Visa versa.:crossfing:

...I know, but look at the pic- it's fresh and clean and I can put in whatever I want :)

Axel:germany:

[joseph m. hahnl]

...I know, but look at the pic- it's fresh and clean and I can put in whatever I want :)

Axel:germany:

If that's the case Big block is the way to go:wink:. Then you don't have to limit yourself to just a 454:kingme:

[Pismo]

Find a 502...