5.7 vs 383 stroker

[BarryTurano]

If I were to repower my 5.7 with a 290 hp output with a 383 stroker say 350 hp, what should I expect? More speed at lower rpm? Improved fuel economy by running at lower rpm? How would torque effect the performance? Not sure what torque equates too. Thanks for the help.

 

[alldodge]

HP makes you go faster (WOT top speed)
Torque gets you there faster (hole shot)

With more HP, can "probably" turn a higher pitch prop and lower rpm, BUT your feeding more cubic inches
Next to no fuel economy increase unless your old motor was not running well

 

[BarryTurano]

The present motor runs fine. I was looking for more speed and better fuel economy. I guess that is not going to happen. I made a 165 mile trip included trolling. I burned 95 gallons. Problem is that I only carry 118 gallons. My way of thinking is that I was cutting it very close. Came back with 23 gallons of fuel. I am thinking that I have 13 gallons usable. Figured that I have about 5 gallons in each tank that could be questionable. Way to close for comfort. I guess I will run my buddies boat to the stream. He has a 25 sea hunt with twin 150's. I think he carries 150 gallons of fuel. The ride is not as comfortable but his fuel economy and range is better.
Thanks for the response.

 

[jimmbo]

Adding an extra fuel supply might be an option. A slightly different speed might increase your range, as will removing any unneeded equipment.

 

[Lubak572]

If I ever get mine done I will let you know. I upgraded my my twin 5.7 GSI 280HP to 6.2 350HP motors on a 31 foot cabin cruiser. I also went with Hardin Marine Seaward series exhaust. Hope to fire up and launch this week.

 

[Scott Danforth]

both motors would burn 0.4# of fuel per HP per hour.

so assuming your loading is the same and your commanded power is the same, you would burn the same fuel on the trip

however with the 383, you would have more power available, you would command more power at some point, and burn more fuel.

you would have a better hole shot from the increased torque, and with a slight prop change, you would have a slightly higher top end.

 

[BarryTurano]

Thank you all for the replies. Bottom line is "It is what it is" the repower will not due what I was hoping for. Adding fuel is not an option because of the available space (no room for any additional tank-age even a bladder tank). The boat is a 24' Albemarle Center Console with a jack shaft. So the motor is under the helm with two 59 gallon saddle tanks on each side of the shaft. Storage consists of 2 rod lockers on the bow and about a total of 10 square feet of storage under the bow on 2 levels. The boat rides incredibly well in any type of sea. She will roll a bit at anchor or on a drift in a beam sea. But that is the trade off with a 24 degree deadrise deep V. So there is my answer. Run my buddies boat to the gulf stream. At my age (70's) if I make 2 gulf stream trips a year that will be enough.:joyous:.
Thank you all for the info.