300 Suzuki repower on a 2520 DV notch transom

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I'm getting numbers right off the Yamaha fuel management system, it is setup for statute miles.

With my old carbed Yamaha 250, I would approach 1 MPG, heavily loaded. Honestly, I have not yet REALLY loaded her down yet, but with moderate loads, including full fuel and 3-4 big guys I'm still around 2MPG.

My boat has two 4D batteries, a lobster pot hauler, cockpit work station, raft and cradle on top, and 40 gallon live well (usually empty). So yes, she is very heavy.

I repowered a year ago an looked hard at tthe Suzuki 300, the 2520DVSC can use the power. My problem was my faith and proximity to the dealer and they wanted alot more money ( the 300 wasn't quite out when I pulled the trigger).

Looks like your looking for 6500 RPM , WOT ? Defineately keep playing with the prop until you are content. I tried maybe 3 or 4 until we got it right.

Good luck and keep us informed.
 
I'll concede that your boat is way way loaded, perhaps overloaded even for a 300hp OB. 8 guys with all that gear probably requires twin 200hp OB's.
 
The top end seems appropriate for the additional 50HP. Based on the DATA presented, you would have to assume that the Zuke is not as efficient as the Yamaha.

Although I'm partial to Yamaha, I'm still not sure we have accurate data to go by. So, let's wait and see.

I'm hopeful that a 2520DVSC with a state of the art 4 stroke will achieve 2+ MPG, at "higher crusing speed". These hulls run better at 24-25 knots than at 20-22 so we need an efficient plant with extra power. Maybe the Zuke 300 is the way to go, maybe not ? The Yama 350 numbers aren't all that impressive.
 
John, I edited my post, it should have been 6 fishermen plus myself.

The first day I ran the Mirage prop with only two of us in the boat I was impressed with the way it ran. When you convert the numbers from that day to statute miles, we were getting 2.2 mpg @4500 with a speed of 27 mph. That was loaded light with a little tail wind. I think the potential is there. I just have to find the right prop.
 
Thanks for keeping us up to date on your progress. I'm currently waiting for a16x17 to come in, apparently they are backordered till may 20th. I'm also thinking about possibly going for a mercury rev 4, I'll be interested to hear your results on both raising the motor, and the 4 blade.
 
Fishinfireman: 2.2mpg lightly loaded, 2 guys, and a slight tail wind would definetly dissapoint me. I can't lie to you.

I would think you can do more tweaks for sure. I can get 2mpg out of my 250hp Ox66 under the same conditions and I have an Armstrong bracket.

I think things will improve for you as you make more changes. I betcha you can get 2.5mpg out of her. Keep working at it !


John
 
I fished Saturday with a party of 5 and myself on the boat and it was one of the sloppiest days I have fished in a while. I don't think raising the motor did much if anything but it was really too rough to tell a whole lot since I could not trim out the boat for economy. I only averaged 1.2 nmpg for the day. At least the fishing was good.

I will keep working on it until I get this thing dialed in. The Rev 4x17 should be here soon.
 
Maybe you should put a 2.29 gear ratio on it ..... If you always run that loaded. I don't know what it would cost to change the gears... or just get a 250 lower unit.
 
I would check your RPM's with that which Suzuki reports on Fuel Burn.

There should be a few bulletins out there showing this. If you're burning a lot more at 4500RPM's than one of those bulletins, then the problem may be in your motor.

1.2nmpg doesn't seem kosher to me. That's close to the worst my 250hp Ox66 would get, and that's loaded down in very heavy seas.
 
FYI,

I switched from a 17 to an 18.5 pitch last night. No issues getting out of the hole, wot 6000 rpms.

Looking like my 4000 rpm cruise speed went up 3 knots or so. It was tough to quantify as the river was flowing hard too.

Definetly a different feel to the boat all around going from slightly under pitched to perhaps slightly over pitched.

I'm hoping this improves my fuel efficiency a little more.
Looking like some serious weather for the weekend so it may be a while before I decideif I like it or not. Not bad for 100.00 purchase off the THT.

Also, looking at the Zuke web site it doesn't seem intuitive....

The DF 250 burns 10.5 gph @ 4000 and the 300 burns 7.85 GPH ?

Tso does the 100HP burn 20GPH at 4000 ?
 
John, I think throttle setting has more to do with fuel burn than engine rpm's. If you are way over propped you will need more throttle to achieve the same rpm as a correctly propped motor. Here is a link to a post from Ken@propgods on THT site that is interesting. Read Ken2's post. It's about 3/4 down the page.

http://www.thehulltruth.com/forums/thre ... 4&posts=15

I am sure I can get better economy from this motor once I find the right setup. I will keep you all posted with my progress.
 
Harpoon: To be honest, unless I see things improve a lot with the 300hp on the 2520DV, it will be awhile. The payback from my Ox66 to a 300hp Suzuki seems very very long. From a dollars and cents view, not a no brainer.

The 250hp Ox66 is a very gutsy strong, reliable engine. I'm happy with mine. Show me where I can get 2mpg in heavy seas, loaded down, and I might look at the next engine.
 
For me. I wanted to get out of the 2 stroke while I could still get a few bucks for it.

I don't have a fuel managment system but I have seen a nice improvment in fuel burn. I expect to see more with the higher pitch prop.

The really sweet thing is the power drifting and trolling... up here the slower the better and that 4stroke will purr all day.

I was kicking myself a little for not waiting another season and getting the 300. After seeing this guys results in FL I almost think the 250 with its 2.29 ratio is probably better for a single engine/large boat application.

I had a ton of great hours on my OX 66 and it is still going...
But I honestly have no regrets changing to the 4 stroke. It has been all positive.

I am chomping on the bit for some time off shore !!! I cant get the weather and my scedule to cooperate !
 
I was also wondering if the 250 suzuki with its lower gear ratio would be a better fit with a heavy offshore boat. I like the 300 very much!!! just curious.
 
YES...this is the correct prop. I just added about 2 knts to my cruise at 4100 rpms. Now about 20kts. WOT 33knts @6000 rpm. About 26-27 kts at 4500rpms.
 
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