2000 Gulfstream with 2005 F225 Yamaha prop recommendation for fuel economy

[ChesapeakeMike]

Is it worth it to move up to a 4 blade Yamaha prop for better fuel economy? Boat came with a Yamaha Saltwater II series 15 1/4 x 17M 3 blade. Read lots of general articles about 4 blade props and their fuel economy being better than 3 blade props. Use my boat about 50 hours a year on the Chesapeake normally for a few hours after dinner for fishing. Not many long distance trips. Any advice is greatly appreciated! Love my 232 Gulfstream!!!

 

[vocz]

I run a pair of Revolution 4 blades 15 1/4 x 17 on my Express 265 w/ F225’s. They are so so much better than the 3 blades. Fuel economy is minimal was 1.6, now 1.8 miles/gal. But the hole shot and midrange is beautiful and boat is 3 miles faster top end!

 

[Ekea]

i would call ken at prop gods. he actually chose 3 blade props for me and i have been very happy. i have twin 250s and can cruise at 27-34 mph while getting 2.2-2.5 miles per gallon

 

[seasick]

How you use your boat is the biggest factor in doing a cost benefit analysis for new props.
4 blade props are typically less fuel efficient at higher speeds because that have more drag than 3 blades.
If you troll a lot that will affect prop choice. Since you say you boat about 50 hours, I suspect you don't.
The two things that you can address to improve fuel economy is to have a clean smooth hull and reduce weight. The easiest way to reduce weight is to not fill your tank all the time as opposed to add as much fuel as you will need for the next outing or two plus a safety margin. It will also help to remove any gear that you really don't need.
I find that repropping is often done to improve performance in the situations that your boating encompasses and not so much for better fuel economy.
One caveat is that the analysis assumes that the current propping is not terrible meaning that your current propping is reasonable.
Your current numbers on setup, burn rate and boating style will be helpful in making a good assessment.

 

[Sardinia306Canyon]

Yes, this correct!
Depending on boaters use the correct 4 blade prop can positively affect fuel efficiency but mostly either in low and mid range RPM's and it depend how well the actual propeller works. A test ride writing down rpm-speed-fuel flow in 100 rpm steps from idle to wot will provide the data to analyze how actual propeller behaves, give a baseline for a prop pro to recommend a new propeller and see variations with new propeller/s.
6-8 knots trolling can make a big difference, but due limited fuel flow financial benefit is low and arguable
24-28 knots cruising with the correct 4 blade can make a big impact on fuel flow, or not so much. The point is that 500 rpm less at +/- 3500 rpm and 25 knots will save enough to make it worth to use a 4 blade prop.
If the boat is usually used light a drop of WOT rpms down to about half of recommended wot rpm range can help also to lower fuel efficiency, particularly in combination with a correct sized 4 blade if highest speed is not desired.
One thing to consider is that chasing the right propeller can be a time and money consuming job and an experienced prop guru may help to keep that less painful.
One prop to consider is the Mercury Enertia Eco where a lot of users are very happy with, other propellers are
Suzuki 16" 3 blade propellers but with 2" less pitch (what I did), Suzuki props are direct swap on Yamaha shafts.
Mercury Revolution 4 as first hand experience is written above probably also with 2" less pitch
PowerTech OFS4 or similar Model, as Ken of Propgoods about the correct model for your boat and Engine.
Solas Titan 4 blades work well and are affordable

I switched from single 19" Saltwater II to Suzuki 18.5" 3 blade on my 30ft RIB but F250 could not turn more than 4200 so Suzuki 17" should do the trick.

Chris