Twin yammy mpg question

[Sagedaddy]

I’ll preface this by saying I know it’s an apples vs oranges question. I know each boat, motors, prop, load etc is different. Just looking for a rough average. I have a 24’ radon with twin Yamaha 150s(2016’s). Just repropped because my previous 3 blades only got me to 5000 max rpm so I knew I was running the wrong props for the heavy boat. Switched to 4 blade powertechs. I can’t remember the specs and I’m not home to check. The responsiveness and planing speed seems to be decent. Anyway I’m able to now achieve 5800 max rpm but it seems that my power curve is now up around 4000+ rpm and I’m only doing 1.5-1.65mpg as best case scenario. Again I know there’s a ton of variables but what are you guys getting for fuel mileage with similar twin set ups? I seemed to get better fuel economy out of my last props but not being able to max out over 5k rpm scared me since i had heard that I was stressing the motors excessively. I obviously don’t run the boat anywhere near max rpm but,again, I had heard from a couple knowledgeable people that only being able to max out at 5000 rpm was indicative of having the wrong props. Thanks I advance for the info.

 

[PACIFICPUNISHER]

Have you played with the outboard height? Most 4 blade props like to be run up higher in the water, you could possibly gain a little mpg if they can be raised. Ive owned a couple f150s on different hulls and none seemed to do well with 4 blade props. If you where getting better mpg with 3 blade props with 5k max rpm vs 4 blade props with 5800 rpm then you still dont have the right props. More details on the boat and prop pitch / diameter would help.

 

[Sagedaddy]

Just got home and checked the specs on the props. The new 4-blade powertechs are 14 1/4” diameter with 14 pitch. As stated the boat is a 24’ radon with and Armstrong bracket and twin 2016 Yamaha 150s. The 3- blade props that I had on before are “turning point” and are 14 1/4” diameter and 17 pitch. I hope that clarifies a bit.

 

[PACIFICPUNISHER]

If the outboards are on a Armstrong bracket you should be able to raise them 1 or 2 holes, verify that they are not to deep in the water.

 

[PACIFICPUNISHER]

Do you recall the mpg # with the 3 blade props?

 

[Sagedaddy]

Seems like I was more commonly around 1.8 mpg. I’m thinking about trying my old props again just to see what I was getting even though I know they’re not the right props considering the fact that I could only reach 5k max rpm. Just trying to figure out what I should possibly be seeing for fuel economy. I’ve only ran a single outboard on previous boats so I’m not really sure what a reasonable expectation would be.

 

[gecsr1]

your running higher RPMs through the spectrum so you are burning a little more fuel.
also try a 3 blade same diameteras your old 3 blades but 15 pitch

 

[benrd81]

I'm running a 26' deep v with twin 3.3l 200hp and see anywhere from 1.3 to 1.5 depending on load running 4 blade OFS4's 15p.

The previous props you were running were slowly killing your motors trust me I found out the hard way and had to replace the cranks when the thrust bearings failed. Make sure you are able to spin them up to the high side of the rated rpm's.

 

[Sagedaddy]

Thanks for the info. I’d like to try to find a happy medium but the current props may be the way to go. Any other info on other boats and burn numbers would be greatly appreciated.