fuel consumption query.sundancer 330

gregkjones · Mar 3, 2011

Carpedmman said:
Ok, As twin 7.4L, Bravo III owner here I better chime in and say that the sweet spot on this set up is around 3200 RPMs. This RPM with 1/4 trim up and with no tabs down runs the boat at 32-34mph. Again, right around a 1 mpg.

I dont know how some people get good numbers with the tabs up but some do. For you though all bets are off because you have the Bravo III's and we already know the performance gains there are significant. You are getting 10mph more than me at 3200RPMs. Hell my boat's max speed is around 35mph and and fuel consumption? I refuse to calculate it, wont do it, do not want to know or I will never use the boat again.

Like your boat, 3200RPMs and trim tabs full up is also my sweet spot, but only if I want to set up a zip-line from the bow to the stern. But seriously, right now I guess the best sweet spot would be 3600 RPM trim full down and wallet full open.

I have seen many people here very happy with the bigger tabs taking care of this issue. I cant wait to see.

Carpedmman · Mar 3, 2011

gregkjones said:
I dont know how some people get good numbers with the tabs up but some do. For you though all bets are off because you have the Bravo III's and we already know the performance gains there are significant. You are getting 10mph more than me at 3200RPMs. Hell my boat's max speed is around 35mph and and fuel consumption? I refuse to calculate it, wont do it, do not want to know or I will never use the boat again.

Like your boat, 3200RPMs and trim tabs full up is also my sweet spot, but only if I want to set up a zip-line from the bow to the stern. But seriously, right now I guess the best sweet spot would be 3600 RPM trim full down and wallet full open.

I have seen many people here very happy with the bigger tabs taking care of this issue. I cant wait to see.

Greg- I meant nothing other than to post my fuel usage at 3000-3200 rpms since it is unknown if the OP has I/O or V-Drives. Please don't take offense as I only offered my 2cents. 3100-3200 is my "normal" running RPMs hence the reason I know my numbers.

VinceR · Mar 3, 2011

I think you will find better performance with full down tabs.

The Maestro · Mar 3, 2011

Hi,thanks all ,for info.Yes running salt water,props tuned,bottom spotless,my 330 not a european model,I imported from Punta Gorda.Am averaging around the 1gall/mile though.Cost fuel here is at £1.35/litre deisel at £1.39!!!
May try a bit more of the cocktail speed!!!
VinceR fuel flow numbers are interesting.Being fairly new the forum here is where I am picking up a lot of tips.Thanks.Neil

gregkjones · Mar 3, 2011

Carpedmman said:
Greg- I meant nothing other than to post my fuel usage at 3000-3200 rpms since it is unknown if the OP has I/O or V-Drives. Please don't take offense as I only offered my 2cents. 3100-3200 is my "normal" running RPMs hence the reason I know my numbers.

Not offended at all, just hurt.....just hurt. No, I am kidding. Not offended or hurt. Actually I didnt notice the OP hadnt stated what he had, Vdrives vs B3s. I love the 330s with the B3s, they have great performance and I know how to work on the drives. Vdrive trans. are still a mystery to me. I cringe at the idea one of those breaks, but heh they shift real smooth. I guess that counts for something, not sure what but..

dpmulvey · Mar 3, 2011

Here is the modification I did on my trim tabs.

I too used to have to run at 3600 to 3800 RPM's with full tabs to keep the nose over to the proper planing attitude. Speed was roughly 22 knots. Fuel consumption was roughly 25GPH (Recall I have 6.2L Horizons with a 5300 WOT RPM.)

I had the props scanned and made the tab mods. After the change I cruise at 3300 to 3400 RPM's with roughly 1/8 to 1/4 tab to hit 22 knots and consume 21 GPH.

Well worth the time and trouble.

gregkjones · Mar 3, 2011

dpmulvey said:
Here is the modification I did on my trim tabs.

I too used to have to run at 3600 to 3800 RPM's with full tabs to keep the nose over to the proper planing attitude. Speed was roughly 22 knots. Fuel consumption was roughly 25GPH (Recall I have 6.2L Horizons with a 5300 WOT RPM.)

I had the props scanned and made the tab mods. After the change I cruise at 3300 to 3400 RPM's with roughly 1/8 to 1/4 tab to hit 22 knots and consume 21 GPH.

Well worth the time and trouble.

You know what, your post is what gave me the idea quite awhile back. One thing I was wondering is the thickness of the sheet you used??

I am going to the metal shop tomorrow to look and think the .120" would be right, but again I need to get my hands on it to verify. Your tab idea is exactly what I am doing.

dpmulvey · Mar 6, 2011

gregkjones said:
You know what, your post is what gave me the idea quite awhile back. One thing I was wondering is the thickness of the sheet you used??

I am going to the metal shop tomorrow to look and think the .120" would be right, but again I need to get my hands on it to verify. Your tab idea is exactly what I am doing.

Sorry for the delay in responding.

The stainless was closer to 1/4 inch. It was left over from a fuel tank my welder built. I was lucky that the welder had years in the business and was a boater as well. I figured using the same thickness as the tab would suffice. I was wrong. Mine are very heavy and I was very concerned about even more weight in stern, however they do the job very well.

Sayat Tomarci, our member from Turkey with the diesel outdrive, used stainless approximately the same thickness as
his tabs. He had all kinds of vibration problems that required "spines" to stiffen the tabs.

I

Gofirstclass · Mar 6, 2011

You guys with the 7.4's will have to use more tabs than the guys with the small block engines just because of the extra weight of the larger engines.

On my 330 I used about 1/2 tabs and it stayed on plane just fine with full fuel and water. If I had light fuel and water loads I could get by with about 1/4 tabs. .

magster65 · Mar 7, 2011

Tab mods :thumbsup:
Many years ago I did that to an old tail draggin' boat I had... it made a huge difference.
Just on a side note if you contact Bennett... they have various sizes of tabs that are "flawed". If you don't mind some scratches... they're about 1/2 price.
Remember... if you double the size of the tab, you more than double the pressure on the actuators because of where they mount on the tab. The more tab past the actuator mount, the more leverage is at work...

melida · Mar 7, 2011

dpmulvey said:
Sorry for the delay in responding.

The stainless was closer to 1/4 inch. It was left over from a fuel tank my welder built. I was lucky that the welder had years in the business and was a boater as well. I figured using the same thickness as the tab would suffice. I was wrong. Mine are very heavy and I was very concerned about even more weight in stern, however they do the job very well.

Sayat Tomarci, our member from Turkey with the diesel outdrive, used stainless approximately the same thickness as
his tabs. He had all kinds of vibration problems that required "spines" to stiffen the tabs.

I

gregkjones · Mar 7, 2011

Thank you dpmulvey and melida. Excellent info. Appreciate it.

dpmulvey · Mar 22, 2011

Hello Melida. How are things in Turkey?

Glad we can get together to help another SR owner!

Larry,

PowerPoint slide as promised. Hopefully with Melida's pictures and the slide, you will get an idea of what my tabs look like. The angles are cut and sharp edges ground down, merely to avoid any cutting hazards.

You can practice on some construction paper from a craft shop to get comfortable. My welder has been in business for over 20 years and boating his whole life. I gave him the design and he ran with it.

Good luck and please feel free to contact me if you have any questions.

fuel consumption query.sundancer 330

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