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DF200SS lower unit swap (2.5:1 to 2.0:1) and a lesson on gear ratios

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  • DF200SS lower unit swap (2.5:1 to 2.0:1) and a lesson on gear ratios

    Hey all,

    This will be long. Apologies.

    I know the bass boats aren't really a dominating presence in Suzuki use cases, but I've decided to make this post to help any others in a similar situation.

    Over the past few years, there have been several instances where a small agile hull was paired with the Suzuki DF200SS (a reskinned DF200A). Most common of these cases are bass boats. This combination has been demonstratively proven to be sub optimal. The lower unit gear ratio had very short gears compared to competitors. While these short gears (higher numerical ratio) were efficient for large hulls such as pontoon boats or large off shore rigs, they put a performance cap on smaller hulls. Small, planing craft already have efficient hulls. Their need is enough torque to get them out of the "hole", and then enough power to spin a smaller prop very very fast. This is why you see popular outboards such as the Yamaha SHO or the Mercury Pro XS on bass boats. These sport tall gears (smaller numerical value) such as 1.85:1 or even 1.75:1.

    In the case of the older model DF200SS, the 2.5:1 gear ratio makes it very hard to prop. I run a 27 pitch prop that it easily turns past the WOT limit. I have heard of cases where people were using 28, 30, even 32 pitch props. However, you can only go so high in pitch before you lose out on theoretical performance and overall speed. What's frustrating is hearing so called experts (some of which exist on this forum) claim that "you are just propped incorrectly". That sentiment is certainly false, and I wonder how many people have fruitlessly bought props based on advice here. A common sentiment echoed is "your prop does not have enough diameter". Sweeping statements like these are lazily thrown out. Propping is a complicated process, and yes, while diameter can affect performance, if your prop slip percentage is already low (bass boats typically have around 10%), you can't expect it to make up for performance found in other outboards. For example, my F195 with a 200 Pro XS or a 200 SHO is capable of reaching speeds in the high 60s and low 70s. These are numbers directly from dealers and the manufacturer. With my DF200SS? I've only managed to get 57 mph at 6200 rpms. That's a 10 percent slip. And a ~13 mph deficiency in speed compared to competitors. Not good. Finally, Reliable Marine has stated in conversation to me that Suzuki themselves figured out that it was impossible to use pitch to gain speed past a certain point. Shaver Marine in talks with me declared the max speed they saw on a 2.5:1 ratio DF200SS was 55 mph, and was slightly skeptical of my 57 mph claim.

    Of course we hear the irrelevant arguments about "why do you need to go that fast". I paid for a 200 hp outboard, I expect performance reflective of a 200 hp outboard. That's all that needs to be said.

    Suzuki finally pulled their head out of their ass and realized offering a DF200SS, which is marketed towards bass boats, but not actually having any difference from the DF200A, was asinine (and in my humble opinion, disingenuous). 2020 and later models had an updated gear case with a 2.0:1 gear ratio. While still not ideal (they really need to be copying Merc and Yam and going 1.85), it's a drastic improvement from the 2.5:1. Reliable Marine in Miami said Suzuki told them to expect an average of 8 mph speed increase on smaller craft. Shaver Marine in Pasadena Texas also reported successful repowers on smaller craft. Doss Marine (South Carolina) was less optimistic, saying that 18-20 foot bass boats did see a speed increase, but the torque curve on the motors did not allow for large pitch props to be run, citing hole shot issues. This lowered the speed increase as they had to run smaller pitches than anticipated. Finally, there is scant anecdotal evidence online. Very very few people have this new lower unit on small craft. The few I've talked to said they were able to run larger pitch props provided that they were vented, to help spin up on hole shot.

    So, all this long winded (but hopefully informative) ranting concludes with me buying a DF200SS complete updated lower unit (50020-96Y10-YAY). It arrives Wednesday and I hope to throw it on my DF200SS on a 19.5 foot bass boat. I'll be running with the same 27 pitch 4 blade except this time vented. Both Mark Croxton Propellers and Powertech told me to run the 27 first (I was apprehensive). I need a baseline anyway and they said I could be pleasantly surprised. THEORETICALLY, this should get me to the mid 60 mph top speed and beyond, but we all know the practical and theoretical have a tenuous relationship. The reported strange torque curve does scare me a little, but I have heard promising results with Mercury props vented (the 3 blade Tempest specifically). While part of me does think about the possibly of wasting my money, I'm reassured by that fact that I at least have to try. Someone has to take the plunge. Will be updating this thread with results soon hopefully.
    Last edited by th365thli; 01-10-2021, 01:40 PM.