Difference in gas usage 305 verses 165 HP.

[halas]

Is there a big difference between the 305 Chevy 8 cyl. and the 165 Hp inline 6 cyl. gas usage?

The 305 Chevy is in a 1978 21' Thompson Fisherman and the 165HP inline 6 is in a 1974 Duo Challenger. Both are similarly built, looking at the pictures on EBay. Both have 8? beam and very deep V hulls for the Great Lakes.
The 20? is plenty big for me but like the 21? Thompson better only if the fuel economy is similar.
What kind of gas mileage can I hope for in these?
We all know that the gas will go up again sooner or later.

 

[Bondo]

Re: Difference in gas usage 305 verses 165 HP.

Ayuh,...
Smaller motors burn less fuel,...
But I don't think I'd base my boat buying on fuel mileage alone,..
Matter of fact,... It'd be the Last thing thought of....

 

[chiefalen]

Re: Difference in gas usage 305 verses 165 HP.

Thats a good question. So lets try to reason it out.

2 boats weighing the same ( almost ).

2 boats same hull ( almost )

l6 in my humble opinion will have to work harder to push the boat say 20 mph.
Say thats the speed you wish to maintain, for this example.

The 305 would work less, and run at less rpm.

Maybe a wash in the case of fuel usage.

If i were in your position all things being equal i would take the 305, you never know if or when you might want to goose it, or pull a water skier, or tube.

When i posted all things being equal as in how well maintained the boats are.

One other factor the 305 is going to be easier to find parts for and replace.

Good luck !

 

[45Auto]

Re: Difference in gas usage 305 verses 165 HP.

Fuel economy will be so close you'd have a hard time telling the difference. In this case overall condition of the engine/carb/ignition will probably make more difference than the displacement. Expect 4-4.5 MPG at best cruise speed with either engine.

 

[halas]

Re: Difference in gas usage 305 verses 165 HP.

Thanks for the useful insights. I just wanted to make sure not to make mistakes while buying a boat.

 

[Bondo]

Re: Difference in gas usage 305 verses 165 HP.

Thanks for the useful insights. I just wanted to make sure not to make mistakes while buying a boat.

Ayuh,.... Rule #1,... Don't buy a boat powered by OMC.....

 

[halas]

Re: Difference in gas usage 305 verses 165 HP.

Is this an OMC motor? Mercury
Year: 1974 Engine model: 165hp inline 6

 

[Bondo]

Re: Difference in gas usage 305 verses 165 HP.

Is this an OMC motor? Mercury
Year: 1974 Engine model: 165hp inline 6

Ayuh,... Donno,.. You never said....

If it's a Mercruiser Drive,+ Motor,... Go for it, parts are Redily available....

If it's OMC,... Forget it....

Btw,... Mercury builds Outboards,... Mercruiser builds I/Os.....