See full version: Lower Units
We buy Lower Unit Cores The busy summer season will be winding down soon and we begin looking ahead to next year. As one of the top remanufacturers of lower units in the US, we spend much of the winter months rebuilding gear cases so they are ready to ship out at a moments notice. In order to … Read more
Our product highlight for this week is the popular Remanufactured Volvo-Penta SX-M Upper Gear Case from US Boatworks. We offer the SX-M in two popular tooth counts, the 22/23 and the 21/26. Within the 22/23 Upper, you can choose from five different gear ratios. Those are 1.43, 1.51, 1.60, 1.66 and 1.85. As for the … Read more
Prevent the tragedy of getting stuck out on the water. Eliminate down time and weeks at the boat repair shop this season. Buy the best boat parts now. You will thank us with many trouble free days out on the water. Properly maintaining your boat engine is important to the life of your motor. An … Read more
US Boatworks now proudly carries the hard to find Volvo Penta DPS-A gear case in several different configurations. Our remanufacture department has been hard at work this winter to make the quality Volvo Sterndrive Housings in the following specifications: DPS-A LOWER (17/29) 1.78 RATIO, OEM#3842842 DPS-A LOWER (17/29) 2.11 RATIO, OEM#3842842 DPS-A LOWER (16/30) 1.95 … Read more [links]
There seems to be a misunderstanding about gear ratios among some people so I'll try to explain!
For lower units with a 2.0 ratio the engine turns 2 times for every revolution of the propshaft, (e.g. 2.0:1).
A 1.75 ratio the engine turns 1.75 times for every revolution of the propshaft, (e.g. 1.75:1).
A 1.62 ratio the engine turns 1.62 times for every revolution of the propshaft, (e.g. 1.62:1).
A Higher ratio = more engine rpm for the propshaft's rpm, (a Higher Ratio not a higher speed).
If you lower the gear ratio enough you'll be at 1 to 1, (direct drive).
Lower it even more and you'll be in overdrive which would put the propshaft turning faster than the engine!!
To further explain, which is the higher ratio, a 30:1 or a 1:1?
I'm sure at some point this has been discussed but. Here We Go Just in Case!
The ratios in modern Mercury lower units are 2.0, 1.87, 1.75 and 1.62. These are based on the propshaft's "ONE" revolution! E.G. 2.0:1, 1.87:1, 1.75:1 and 1.62:1
In general a higher ratio gearset will leave harder because the higher ratio gear lets the engine rev faster getting into it's torque band sooner!
The gereric terms which people have used for years for gears are Low gears and High gears but in actuality the actual gear ratios are just the opposite. i.e. a Low gear is a High Ratio and a High gear is a Low Ratio!
WillySteve Hendricks
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I see that Terry g replied to your post over on BBC as well where you asked the same question. He has offered some good suggestions there as well. [links]
Do they make gears to change the ratio in the lower unit to something around 2:1 or lower? [links]
I agree that you can get more than what you are getting. I hit 56 with my Skeeter SL190 - Yamaha F150 with stock 3 blade, (pretty much the same boat as you have) but only 54 with a 4 blade - both reach 6,000 rpm. and, IMHO, 60mph in such a light boat can be pretty scary - but that's your choice.
I agree that you can get more than what you are getting. I hit 56 with my Skeeter SL190 - Yamaha F150 with stock 3 blade, (pretty much the same boat as you have) but only 54 with a 4 blade - both reach 6,000 rpm. and, IMHO, 60mph in such a light boat can be pretty scary - but that's your choice.
There is a DF250 that has a 2.08:1 gear ratio and I thought about swapping lower units or ordering the gearset from that engine's LU to swap into mine if it will fit.
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 here
This will be long. Apologies.
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. [links]
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. more
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.
for example: the lower unit part numbers sometimes only varies one digit in the last 4,
ex: 2001 50tlr = 63d-45300-12-4d then
2000 c50tlry = 63d-45300-11-4d the only difference is the 11 and the 12, here
HI, new to forum I am searching for a lower unit compatibility or cross reference chart, or does it even exist.
I have a 2006 50tlr with a bad lower unit. prolly not rebuild-able. [links]
also does a chart identifying what each position definition for the part numbers exist more
this information would be invaluable, physically looking at them I really see no difference, so if yamaha changed from 11 to 12 because of color or something, cool. But if it is due to something like shifting rod from push pull to twist, or mounting dimensions, well then not so good. or if its different gear ratio, that could get interesting.