Fuel economy of 1995 Yamaha 175

[Osprey]

I am running a 1995 175 Yamaha on a Grady White 208 20.5'. This is a new boat for me and had not been used in the past two to three years. In wind/chop conditions it appears to get about 1.8MPG and in good conditions about 2.2MPG. Does this seem about right? Should I factor about the same economy when trolling?

 

[swist]

Re: Fuel economy of 1995 Yamaha 175

Kinda need more data.... If you mean at most economical cruise it gets 2mpg, that seems low - if you are doing 30 mph, that would translate to 15 gph fuel usage. Although one of the drawbacks of Gradys is they are very heavy compared to other makes, I don't think that would account for it.

 

[vinney]

Re: Fuel economy of 1995 Yamaha 175

Yes Its right on. A carb 175hp. will burn 17.5 gal./hr at WOT. Base HP. divided by 10. 175/10. EFI. Base divided by 25. DFI base divided by 35. The biggest reason for poor fuel economy is the correct prop(wrong prop is installed) or spun hub on the prop your running. On average If we take off a 250 carb Yamaha and install a Yamaha HPDI 250 you will almost double the fuel economy and have more than cut the oil consumpsion in half with more power in your hand.

 

[Osprey]

Re: Fuel economy of 1995 Yamaha 175

The MPG listed on the original post is based on a cruise RPM of about 3300 to 3600 RPM's. This seems to be the sweet spot where the engine runs best at cruise. This results in a boat speed of about 18.5 knots in choppy conditions and about 21 in resonable open ocean conditions. Would this seem to be the correct prop? How about what to plan for as far as trolling economy?

 

[vinney]

Re: Fuel economy of 1995 Yamaha 175

To correctly prop a boat. You need the average amount of fuel average amount of gear and average amount of persons. The term that is use is nominal load. The boat should achieve the middle of the recommened RPM. Say 5200 rpms to 5600 rpms. You should achieve 5400 RPM's with nominal load and light trim. Every hull is different and every engine runs alittle different. You have current, wind and hull differences. There is different fuels and different elevations. This why they make so many different props. Good fuel economy in a boat comes from the correct power to weight ratio for your boat. If the boat has enough power to push the hull and you are running the correct prop. You boat will be efficient.

 

[myalibi]

Re: Fuel economy of 1995 Yamaha 175

Check the Yamaha site. They say the Cruise RPM's for a 175 is between 4000 and 4500RPM. I have a 22 ft Stabicraft which is aluminum, so much lighter than your boat. About 3000 pounds. I run at 4500 RPM which puts me at 36mph. I am getting 8gph at this RPM. My max RPM in 5200.<br /><br />If you can't get your 175 up to at least 5200 then you have the wrong size prop. I would suggest changing props. Go to a place that lets you try before you buy so you can get the right pitch.<br /><br />good luck

 

[Osprey]

Re: Fuel economy of 1995 Yamaha 175

I will try the Max RPM test this weekend and post the results. 5200 or bust!