Better fuel economy with F350's?

4

4tb

GreatGrady Captain
Joined
Aug 4, 2026
Messages
2
Reaction score
0
Points
1
Age
41
Model
Marlin
I have a 94 marlin with Ox66 250's. I've been casually looking at repower options. I'm not real serious yet, unless i come across the right deal. I get .08 MGP. I was sniffing around on the Grady White web page and saw the spec for fuel economy on the new marlin. F300's cruse @ 3800RPM @ 29.7MPH, 21.5GPH, 1.38MPG. F350's cruse @ 3500RPM @ 29.6MPH, 17.6GPH, 1.68MPG. I realize these are best case condition averages and will vary with conditions inside and out side the boat. I have no need for more power or more speed. That said when you get .8MPG The Difference between 1.38 to 1.68 (0.3MPH) is pretty significant. I'm also aware my transom is NOT rated for 700HP.
Ok now the question. Are guys with 700HP really getting on average 0.03MPH & 3.9GPH better fuel economy then those with 600HP? Hard to believe. I don't want the weight or the purchase price but id sure love to see 1.68MPG & 17.6GPH!!
 
4tb said:
Ok now the question. Are guys with 700HP really getting on average 0.03MPH & 3.9GPH better fuel economy then those with 600HP? Hard to believe. I don't want the weight or the purchase price but id sure love to see 1.68MPG & 17.6GPH!!
Click to expand...
Yes they are.
An IC engine is a complex air pump. Air will flow better through the engine at specific rpms based on a lot of factors. In this case the f350 is able to make similar power at a lower rpm than the f300 = less go juice.
Some could argue semantics all day, but this is the Cliff's notes version.
 
I'm thinking you'd likely get even better fuel economy numbers than what you mentioned, as you're comparing your boat to a brand new one. When in reality, your boat is a 280 Marlin with a dry weight of 7k lbs, compared to the new ones which are a 300 Marlin with a dry weight of 8,221 lbs. That extra 1,221 lbs of weight that you're saving should once again make your boat even more fuel efficient with the same, or similar motors. I imagine the F300's would likely be just fine, but that's my opinion. Perhaps someone else will come along with a similar setup to what you're inquiring about and give their feedback on the matter...
 
Mustang65fbk said:
I'm thinking you'd likely get even better fuel economy numbers than what you mentioned, as you're comparing your boat to a brand new one. When in reality, your boat is a 280 Marlin with a dry weight of 7k lbs, compared to the new ones which are a 300 Marlin with a dry weight of 8,221 lbs. That extra 1,221 lbs of weight that you're saving should once again make your boat even more fuel efficient with the same, or similar motors. I imagine the F300's would likely be just fine, but that's my opinion. Perhaps someone else will come along with a similar setup to what you're inquiring about and give their feedback on the matter...
Click to expand...
Mustang you are correct, it is a 280 marlin. I normally call it a 300 due to the confusion i get from calling it a 280. And yes 300's or even modern 250's would be fine for me. The heart of my question was really if real world applications were seeing the better fuel economy out of the 350's over the 300's the Grady web pages is showing. although id love to hear some real world numbers from someone with a 280 rockin 300's.
Also, I've been told the 280 is lighter then the modern 300, and that the hull is the same. It was manly the name that changed due to some regulation that was being dodged by calling it a 28' boat and not a 30'. Obviously the top cap has seen some changes, like the modern side windows. Any truth to the hull being the same from 280 to 300?
 
4tb said:
Mustang you are correct, it is a 280 marlin. I normally call it a 300 due to the confusion i get from calling it a 280. And yes 300's or even modern 250's would be fine for me. The heart of my question was really if real world applications were seeing the better fuel economy out of the 350's over the 300's the Grady web pages is showing. although id love to hear some real world numbers from someone with a 280 rockin 300's.
Also, I've been told the 280 is lighter then the modern 300, and that the hull is the same. It was manly the name that changed due to some regulation that was being dodged by calling it a 28' boat and not a 30'. Obviously the top cap has seen some changes, like the modern side windows. Any truth to the hull being the same from 280 to 300?
Click to expand...

I don't know very much about the boats in question, other than the numbers/stats on the Grady White website, which is a wealth of knowledge, especially their archived brochures section. Attached is the 1994 archived brochure, of which your 280 Marlin says it has a centerline length of 28', compared to the new ones which have a centerline length of 30'6". So, between Grady White calling it a 280 Marlin and it having a centerline length of 28', I imagine the two hulls are completely different from one another.

 
You must log in or register to reply here.