Gas use vs prop/type and pitch

[Denise56]

I have an 88 sundancer 268. It has a 3 blade prop.(unsure of pitch.Previous owner didn't know). I am getting poor gas mileage and was told that another Searay owner put a 4 blade stainless steel prop on (again, unknown pitch) and got greatly improved gas mileage. In fact this person, a boat broker, claimed his numbers doubled. Does anyone have any info or thoughts on this?

 

[tbirdvet]

Mercruiser is now putting on 4 blade props ilo 3 blade however they claim better launch and slow speed performance. I would not expect to see much of a fuel economy improvement. Do you know what your fuel consumption is in gph?

 

[Denise56]

No I really don't have exact numbers John. I frequently cruise from Olcott(Lake Ontario) over to Toronto and use almost a full tank of gas. The previous owner with the same miles and conditions used 1/2 tank. I have had the boat for 2 seasons now and have never gotten the mileage he claims to have gotten. The boat broker thinks I should be getting much better numbers due to the size of the engine(doesn't have to work as hard). Any other thoughts are appreciated. Thanks!

 

[tbirdvet]

When was the last time you had a tune up? I would look at the color on the plugs and see if all black (running rich) or light brown (correct color). Perhaps your carb. needs a rebuild.