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Yam F350 - Suz DF350: 2nd direct comparison

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Yam F350 - Suz DF350: 2nd direct comparison

Old 05-21-2019, 06:01 AM
  #21  
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Sorry to say, but maybe the twin counterotating propellers have some responsability in the results ............. after all no outboard manufacurer has chosen (and kept) the twin prop approach neither has any racing team .... just sayin .........
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Old 05-21-2019, 06:08 AM
  #22  
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Originally Posted by Empire View Post
I think the DF350 has growing pains. I'd hold off a little before purchasing. I bought mine August 2018 and at 140 hours currently. Water is in both my lower units. No fishing line! I have a feeling bad design. Also one of my lower units recently started making a horrible clicking sound.
I have a buddy that has a set of DF350's. Same issue with water in one of the lower units. I believe he said there was a known issue and his dealer addressed it.
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Old 05-21-2019, 07:09 AM
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I actually liked mine a lot. For my application they were just what the Dr. ordered. A big boat with twins that needed the grip and stern lift. They performed really well. I realized big gains in economy over the f350s.
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Old 05-21-2019, 07:12 AM
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Originally Posted by MakoMyDay View Post
Mine got faster and faster the lower I mounted them.
So you got better WOT speed when it was mounted lower? (and with increased trim angle then I assume, as you could lift the hull more out of the water?)

And you did not have to change props for it?
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Old 05-21-2019, 07:23 AM
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Originally Posted by CANARIANFISHER View Post
Sorry to say, but maybe the twin counterotating propellers have some responsability in the results ............. after all no outboard manufacurer has chosen (and kept) the twin prop approach neither has any racing team .... just sayin .........
Yamaha has been selling them for 20 or so years
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Old 05-21-2019, 07:29 AM
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Originally Posted by Capt. Fred View Post
Thanks again for posting your results OP. I am considering a single Zuke for a 25 footer sometime down the road and real world results like these are very interesting.

It is too bad they don't have a bunch of different props for you to try, as it seems you would want to be propped to get about 6000 RPM WOT with the Suzuki.

From what others have experienced, it does seem that lowering might help some too.
I can decrease the pitch further to get higher RMPs, but as it does nothing for WOT speed, and decrease fuel economy (need higher RPM for all speeds), I am not going to do that. It's too bad there is only one diameter prop to chose from. smaller diameter with same pitch might have been interesting.

As mentioned, the Yamaha and the Suzuki are two different animals. I like to go far and fast (and get childishly giddy when I can go faster than all the other day cruisers around me) and for that the Yamaha is the better engine. If you like better handling, the Suzuki is great, because of the insane bite in the water of the dual prop.

By the way, for all owners of these big engines: Do as the user manual states; flush the cooling system with fresh water after every trip. I finally read the Yamaha service bulletin about that (hotter exhaust because of increased sulfur because of ethanol leading to salt deposits eating more efficiently through the metals), and I recon it is what killed (or mortally wounded) my F350 after 9 years. I even used the boat for three winters, which meant no flushing for 5 months. No dealers here mention the importance of that, the standard here is to just flush the thing once a year.

I flush the DF350 religiously now, and had I begun doing that 10 years ago I recon my Yamaha would have been still healthy. I guess it is in the manual for a reason.

And on that note: I find the design of the tilt lock on the Suzuki asinine. When you apply it (again, refer to the manual - it is a real issue at least in these parts, you have to do it to protect the tilt unit) it lowers the engine like 20 cm before stopping it, leaving the inner prop and large chuck of lower unit submerged. They should redesign those, making them a bit longer.
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Old 05-21-2019, 07:32 AM
  #27  
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Originally Posted by CANARIANFISHER View Post
Sorry to say, but maybe the twin counterotating propellers have some responsability in the results ............. after all no outboard manufacurer has chosen (and kept) the twin prop approach neither has any racing team .... just sayin .........
Except it is the mode of propulsion chosen by both manufacturers of pod drives when engineering the new product for market, is being added by Seven Marine to their line up, and has been in extended use in both Bravo III and Volvo out drives even though it would have been simpler and cheaper for them to drop the design if it were ineffective. The advantages are pretty well known. The engineering complexities are pretty obvious. There is nothing to be "sorry to say." It is a superior means of propeller propulsion if the technical hurdles are addressed properly. The water in the lower units (if those end up being common) indicates a technical hurdle needs to be addressed better. Of course, being best for many applications does not necessarily imply being best in every application, and it would not be surprising to me if racing is not where the design will shine. The OP is not running a race boat, though.

Back to the OP, the experience of other df350 owners with improvements in efficiency with minimal loss of top end speed indicates there is room for improvement in his set up. If it were a contra-rotating propeller issue, there would not be the improvements being reported elsewhere.
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Old 05-21-2019, 07:33 AM
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Originally Posted by amerelium View Post
I can decrease the pitch further to get higher RMPs, but as it does nothing for WOT speed, and decrease fuel economy (need higher RPM for all speeds), I am not going to do that. It's too bad there is only one diameter prop to chose from. smaller diameter with same pitch might have been interesting.

As mentioned, the Yamaha and the Suzuki are two different animals. I like to go far and fast (and get childishly giddy when I can go faster than all the other day cruisers around me) and for that the Yamaha is the better engine. If you like better handling, the Suzuki is great, because of the insane bite in the water of the dual prop.

By the way, for all owners of these big engines: Do as the user manual states; flush the cooling system with fresh water after every trip. I finally read the Yamaha service bulletin about that (hotter exhaust because of increased sulfur because of ethanol leading to salt deposits eating more efficiently through the metals), and I recon it is what killed (or mortally wounded) my F350 after 9 years. I even used the boat for three winters, which meant no flushing for 5 months. No dealers here mention the importance of that, the standard here is to just flush the thing once a year.

I flush the DF350 religiously now, and had I begun doing that 10 years ago I recon my Yamaha would have been still healthy. I guess it is in the manual for a reason.

And on that note: I find the design of the tilt lock on the Suzuki asinine. When you apply it (again, refer to the manual - it is a real issue at least in these parts, you have to do it to protect the tilt unit) it lowers the engine like 20 cm before stopping it, leaving the inner prop and large chuck of lower unit submerged. They should redesign those, making them a bit longer.
going down in pitch can increase speed in many cases. Would not rule it out, should be closer to 6k rpms at WOT.
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Old 05-21-2019, 08:18 AM
  #29  
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Originally Posted by CANARIANFISHER View Post
Sorry to say, but maybe the twin counterotating propellers have some responsability in the results ............. after all no outboard manufacurer has chosen (and kept) the twin prop approach neither has any racing team .... just sayin .........
Yeah at some point the uber coolness of Suzukis latest bullet may run head first into the unmovable wall of physics....starts with a d and rhymes with rag.

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Old 05-21-2019, 03:15 PM
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I love all the comments from people who don't have/never had duo props. No they are certainly not made for racing, they are good to 70+ max. They do not however, exhibit the negative performance that is being discussed in this thread. One headed to head comparison is a 32 Regulator, Zukes are faster by 3kts, hole shot much greater, more efficient by.2-.3mpg, weighs less an planes the boat several kts earlier. Different boats will have different results and I believe the setup on this particular boat is not quite dialed in. I also agree that the engine is a bit too high.
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Old 05-21-2019, 03:24 PM
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Originally Posted by HTJ View Post
Yeah at some point the uber coolness of Suzukis latest bullet may run head first into the unmovable wall of physics....starts with a d and rhymes with rag.
But if the added drag is more than offset by t followed by hrust then...
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Old 05-21-2019, 03:41 PM
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Originally Posted by MakoMyDay View Post
Loss pf speed at all rpms once on plane as well as loss of top end. For instance at the highest mounting it would do 32 @ 4500 rpm getting 1mpg. On the lowest it would do 38-39 @ 4500 getting 1.1. It wasn't a slight difference. I have a feeling if I could've gone lower it would've been even better. Like the others said-when raised up high, or even trimmed high while mounted low, it would not blow out-just slip a lot
I agree and have a similar experience. With Jack plates, it's easy to see real time. The duo props don't blow out like a conventional prop would do, rather the rpm just goes up. I think what's happening is that the 2nd prop is getting more air when raised and not contributing it's share of the traction at higher heights.
Interesting that using the jack plates in this way, allows one to get on plane with one engine without lugging it excessively, since it doesn't blow out, but rather just increases the slip.
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Old 05-21-2019, 08:38 PM
  #33  
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Originally Posted by alloyboy View Post
But if the added drag is more than offset by t followed by hrust then...
The big trick, and it is one...we can put a Rev 4 or Eco prop on an F350 (or other of course) and get a real (ish) 10% or less slip at cruise and WOT which is damn near impossible to better. The advantage(s) of the duoprop while very real and suit me to a T are not necessarily in speed/economy, or at least don't seem to be.

"Results" can get skewed in a hurry - Joe Boater replaces ABC motor with XYZ and reports 10% better economy/performance.....and no one ever knows if the old bullet was set up half assed right or not.
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Old 05-22-2019, 06:30 AM
  #34  
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Still to be seen if the added thrust is more than the drag caused by the six blades in the water .............. and Mr Jeepman, the fact that Yamaha has had duoprops for 20 years in their line, proves nothing ...... if the duoprop stuff where any advantageous they would have used in their entire line of engines, something that obviously they did not, so they must have a reason for not wanting duoprops in their entire line, also Mr Texas 17, the fact that the duoprop concept has been adopted by some sterndrive manufacturers does not prove anything either, It might have some certain advantages under some specific conditions but that is all, if it where any good under all circumstantaces, it would be more widely adopted by all propelled vehicles including raceboats and airplanes, In my opinion outboard powered boats are usually light and fast and duoprops have always been avoided in those conditions ............. to each its own .......... if more bite to avoid slipping where desired, four or more blades could have been used (which is what Seven and raceboat teams around the world have done) and some weight and complexitys could have been saved ............... time will tell .......... but in no way the pill of " duoprops are faster and more efficient" can be easily swallowed ..........
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Old 05-22-2019, 06:47 AM
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Originally Posted by CANARIANFISHER View Post
.............. and Mr Jeepman, the fact that Yamaha has had duoprops for 20 years in their line, proves nothing ..............
Seven marine also offers counter rotating propellers lower units. As horse power increases, and larger, heavier boats are utilizing outboard power. Getting power to the prop without large amounts of slip becomes harder and harder. 5 and even 6 blade props are starting to become more available, and for many the simple answer is counter rotating propellers. While twin props may not be the best for the racing world, they are by far the best choice for heavy loads. Twin props have been used for a very long time, and now used more and more in the outboard world.

https://www.fishtalkmag.com/blog/sev...w-527-outboard


Now for Yamaha there market is totally different, and anyone who has used a Yamaha TRP in shallow water will tell you it is the difference of 2wd compared to 4wd in the mud. The TRP excels in shallow water use, nothing else even comes close.
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Old 05-22-2019, 09:15 AM
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...by the way, here's hoping that lowering the engine is not the trick - exhaust opening is already close to the water when stationary, and that's with almost no fuel in the tank. This is same stem length as the Yamaha, so it HAS to be pretty low already. Have not checked the level of the ventilation plate myself, but taking it up this weekend for some hull maintanance, so gonna check then.

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Old 05-22-2019, 09:26 AM
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OP, how many hours? My Suzuki 300 picked up
roughly 150-200 RPM’s and “loosened up” about 20 or so hours.
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Old 05-22-2019, 09:34 AM
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Originally Posted by redseacraft View Post
OP, how many hours? My Suzuki 300 picked up
roughly 150-200 RPM’s and “loosened up” about 20 or so hours.
Around 30 by now
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Old 05-22-2019, 10:26 AM
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Originally Posted by amerelium View Post
...by the way, here's hoping that lowering the engine is not the trick - exhaust opening is already close to the water when stationary, and that's with almost no fuel in the tank. This is same stem length as the Yamaha, so it HAS to be pretty low already. Have not checked the level of the ventilation plate myself, but taking it up this weekend for some hull maintanance, so gonna check then.

In your sig pic it looks like the Yamaha was low as shit!
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Old 05-22-2019, 10:29 AM
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I just remembered one important thing--from the factory the Suzuki doesn't trim lower than level. There is a way to make it trim down another 5 degrees or so and it makes a huge difference. Do a search on here, but there's some sequence with advancing the throttle, pushing the start buttons and removing the kill switch that programs out the negative trim limit. It made a big difference on mine.
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