Re: Marine diesel
 

I have seen 3.7 mpg on a 23 with a single engine cruising at about 27. I don't think you will get past 4 mpg with an outboard. The difference is, the same boat has a wot of 48, where most diesels won't go much past 35.

Re: Marine diesel
 

Gradysailfish. Do you have a 25' grady? Was it an i/o new or did you do a convert? What is your cruise mph/burn and top speed? I have heard those 120's burn next to nothing but vibrate pretty badly. I saw the motor drive combo quoted for about 11 grand.

I am guessing your burn combined about 7.5gph at 25mph. Am i in the ball park?

Re: Marine diesel
 

For the question of different outdrives....I know the Bravo I has a different top cap for diesels....it has cooling fins on it. There could be different internal parts as well.