Changing gear ratio of lower unit

[red1gturbodsm]

I have a 2013 DF175 on a Skeeter ZX190 Bass boat. Top speed I am seeing is only about 56mph with a Croxton Razer XL4 30p prop. This 2.5:1 gear ratio is killing my top end speed. A 175 Yamaha SHO uses a 1.86:1 ratio and can see upper 60's for speed on the same boat.

Do they make gears to change the ratio in the lower unit to something around 2:1 or lower?

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.

Any help would be appreciated. I know that 56mph is still fast, but I do bass tournaments and am getting tired of people passing me half way down the lake with smaller or same size outboards.

[RayBersch]

Manufacturer's match gear ratio's to engines for a reason. Why in the world would you want to go through the time and expense of messing with the L/U gear ratio in search of speed? I suggest you start playing with the prop - you mentioned the prop that you are using but not if you have experimented with others nor what your max RPM is. You seem to have a pretty heavy pitch 4 blade that should do well out of the hole and sticking to the water but do you get top spec RPM's? You are not going to get full performance unless you are reaching the top RPM spec. Mark Croxton seems to do a great job with props and makes performance 3 blades that you may try or perhaps a different pitch 4 blade.

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.

[red1gturbodsm]

Manufacturer's match gear ratio's to engines for a reason. Why in the world would you want to go through the time and expense of messing with the L/U gear ratio in search of speed? I suggest you start playing with the prop - you mentioned the prop that you are using but not if you have experimented with others nor what your max RPM is. You seem to have a pretty heavy pitch 4 blade that should do well out of the hole and sticking to the water but do you get top spec RPM's? You are not going to get full performance unless you are reaching the top RPM spec. Mark Croxton seems to do a great job with props and makes performance 3 blades that you may try or perhaps a different pitch 4 blade.

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 have been playing with the prop so much on this engine that it is driving me nuts. This gear ratio really limits my prop selection. For some reason the slip percentage is MASSIVE on this outboard. Current numbers are this:

RPM 6000 (6100 red line), I can actually bounce the redline while trimming
30 pitch 15" 4-blade Croxton Razor 4XL
2.5:1 gear ratio
56mph max
That all equates to a 17.87% slip

The prop I am using is a high grip prop. The slip percentage is very puzzeling to me. Before this prop I was turning a TXP 30p 3 blade and was seeing over 25% slip

[Harper]

How is the mounting height of the motor? Where is the anti-cavitation plate when on plane?

[Moonlighter]

I am fairly isre that most people run 16" dia props with that hp engine. Have you tried any 16" props?

[RayBersch]

I have been playing with the prop so much on this engine that it is driving me nuts.
Before this prop I was turning a TXP 30p 3 blade and was seeing over 25% slip

......I think you are hung up on prop calculators and fixed on the gear ratio as the variable. In theory, your set up could get, at best, 63mph with an 8% slip and 61 with a more likely 10% slip - neither seems to hit your target. But by simply changing the gear ratio in the calculator to 2.0 you could get 78 at 8% slip and 77 at 10% slip - do you really think that is reality? I do not. Slip calculators are theory - many other things enter into actual performance.

The DF250 you mentioned is a whole different engine than yours and someone with greater familiarity with these engines would have to address the appropriateness of a swap out.

But I might help with other info. According to a Yamaha Performance Bulletin for a ZX190 with a VF150, 15 1/8x22 SHO prop and 2.0 gear ratio the top speed was 59 at 6000 rpm - BUT they used a hydraulic jack plate and the ventilation plate height was 5 1/2" above the boat bottom - hint, change mounting height or try a jack plate as well as different props - especially if you have only tried TWO.

Good luck.

[Harper]

Right on, Ray!!

[LPowers]

X2 on the 3x16" prop.

[red1gturbodsm]

......I think you are hung up on prop calculators and fixed on the gear ratio as the variable. In theory, your set up could get, at best, 63mph with an 8% slip and 61 with a more likely 10% slip - neither seems to hit your target. But by simply changing the gear ratio in the calculator to 2.0 you could get 78 at 8% slip and 77 at 10% slip - do you really think that is reality? I do not. Slip calculators are theory - many other things enter into actual performance.

The DF250 you mentioned is a whole different engine than yours and someone with greater familiarity with these engines would have to address the appropriateness of a swap out.

But I might help with other info. According to a Yamaha Performance Bulletin for a ZX190 with a VF150, 15 1/8x22 SHO prop and 2.0 gear ratio the top speed was 59 at 6000 rpm - BUT they used a hydraulic jack plate and the ventilation plate height was 5 1/2" above the boat bottom - hint, change mounting height or try a jack plate as well as different props - especially if you have only tried TWO.

Good luck.

I do not expect to see speeds in the 70's at all. Mid 60's should be attainable. I have a 12" setback manual jackplate that came stock on my boat. Currently running a 2.5" prop to pad measurement. I have tried it lower and higher but this seems to be where I get the most speed without having "blow out" issues.I have used 4 different props in the last year. I have tried the 16" suzuki props and they didn't hook up any better than the prop I am using now. In fact the one I currently have on there now is a 15" and has been the best so far but still not where I want to be.
The gear ratio of the Yamaha 150 and 175 SHO is 1.86:1, not 2:1. There are multiple guys in my fishing club with those motors on the same boat that I have. They are seeing 63-64mph with a 150hp and 67-68 with a 175. I have ridden in them and saw the GPS readings, not the inaccurate dash speedometer. They do not have any ECU chip or reprograms either.
I am not expecting to match speeds of boats with a 225 or 250hp outboard, but it would be nice if I could just match the numbers the Yamaha guys are getting.

[Harper]

If you can't be happy with your Suzuki, seems the logical thing to do would be to trade it for a Yammy. Problem solved.

[Terry G]

1999 Skeeter bass boat - Suzuki DF150 4 blade 28 pitch Suzuki prop
GPS speed @ 5950 RPM = 59MPH.
I think you have other problems

[Terry G]

1999 Skeeter bass boat
Suzuki DF150 gear ratio 2.5 to 1
Suzuki 4 blade 28 pitch prop = 59MPH @ 5950 RPM
I think you have other problems

[Moonlighter]

The Suzuki drive train is fundamentally different to the Yamaha, or any others for that matter. The offset drive shaft and dual reduction makes it so. The general thrust of the design is to run larger diameter and pitch props when compared to similar Hp from the others.

If you apply Yamaha thinking and sizes in props to a Suzuki, it wont work.

Now, I didnt say to run a 16" Suzuki prop. I said that Suzukis in that hp typically run 16" dia props. So it would be logical, i reckon, to try a high end performance prop in that sort of diameter.

Now youve seen another member post their personal experience above running same/similar boat with 150hp and a 4 blade Suzuki prop and gets better top end than you. So there could be other issues at play as well.

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.

So the challenge is to change your thinking approach from one that suits the conventional drivetrain used by Yamaha et al, and try something that will work with the Suzuki.

[Brightwork]

I have a 2013 DF175 on a Skeeter ZX190 Bass boat. Top speed I am seeing is only about 56mph with a Croxton Razer XL4 30p prop. This 2.5:1 gear ratio is killing my top end speed. A 175 Yamaha SHO uses a 1.86:1 ratio and can see upper 60's for speed on the same boat.

Do they make gears to change the ratio in the lower unit to something around 2:1 or lower?

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.

Any help would be appreciated. I know that 56mph is still fast, but I do bass tournaments and am getting tired of people passing me half way down the lake with smaller or same size outboards.

I'm a bass boat guy, so I'm gonna give you a reply from a bass boat perspective (where nobody thinks 60 - 65 mph is scary or abnormal to shoot for-- whether that's good or bad is for people to make up their own minds, no argument here either way, but I'm coming from the same mindset you are)

There is some good info in the replies you originally received to this post, but it does seem like there is also some pushback to your idea of changing the gearset, which is kind of ridiculous considering nobody had any good reason for saying you should forget it other than it's not the Suzuki way.

Fact is there are a LOT of good reasons to run a Suzuki outboard above and beyond the reduction gear, and Suzuki's gear ratio choices have to do more with the fact that they have focused their engineering more on offshore setups than bass boats since they went to 4-stroke technology. Offshore setups don't need top-end speed nearly as much as they need low-end thrust, and they've picked gear ratios that do that exceptionally well-- they just haven't engineered separate lower units for the bass boat market that have lower gear ratios mated to their engines to achieve better topend with similar props-- there is NO reason they couldn't-- they just haven't. Suzuki has struggled in the US for years and it feels like they have gone through a bunch of presidents in recent years. They're getting back into the bass boat market little by little, but most of that is just marketing-- pro sponsorships and some SS badging on identical outboards as a marketing ploy.

So, if you did try to swap out the gearset, I'd love to hear about how it went. If you haven't tried it yet, you'd mainly want to talk to an actual Suzuki tech to find out if the 2.08 gearset is directly compatible with the DF175 lower unit. i.e. Will it fit. Also, is the intermediate reduction gear the same in both engines-- if not the final ratio might not still be the same. (If everything is equal on those two points, I'd go for the 2.29 gear set of the DF225 if it was me-- a better middle ground on keeping the wide diameter/highest pitch prop option. I'd be worried with too low a gear ratio on the 4 cylinder motor you'd never get to your max RPMs with the bigger props, so 2.29 lands in the middle between the standard 2.5 and the 2.08 you're looking at from the 250SS.) Keep in mind, if you do this, you're probably going to void your warranty.

If you try a swap, let me know how it goes. YES, in theory, a lower gear ratio should help your topend if you can get the motor setup where it will hit the rev limit first. That's a matter of your individual bass boat-- weight distribution, motor height, trim, hull design, etc. Don't compare your numbers to other people's bass boats-- even other skeeters. Get your boat set up where it hits the rev limit with the widest, highest pitch prop you can, record the speed and time to plane, then try the gear set change with that same setup. That would be the way I would approach it. I've never done it, but I'd love to hear from you if you try, because I'd love to put a Suzuki DF175 on a BassCat Sabre FTD, and the 2.5 gear ratio is the main drawback for a hull that efficient-- you could just never see the kind of speed that boat or that motor is really capable of in that combination. If Suzuki would offer the motor in just a little bit lower gear ratio, it would be an awesome setup for the Sabre FTD with Suzuki's big diameter/big pitch prop options.

All of the above is just for whatever it's worth, and no offense intended to those who suggested it's a waste of time or against Suzuki's philosophy in some way. IMO, it's just a more bass boat oriented Suzuki way.

[th365thli]

Reviving this old thread because I actually am encountering a similar situation. DF200SS with a 2.5 to 1 gear ratio. I'm getting 60mph with my current prop, I know my boat can push 70 easy with merc or Yamaha.

The real kicker here is that Suzuki actually released an updated version of my motor with a 2.0 to 1 gear ratio! I called my dealer and they said they wouldn't recommend because of price. Its 3 to 4k for the new lower unit, which honestly aligns with my expectations. I may call them again later about doing a lower unit swap.

The upside is that with the low end torque our bass boats SHOULD have wicked holeshot. I'm currently trying to find a right prop and just ordered a 27 pitch razor xl from mark. I will say, looking at the original posters numbers, even with the gear ratio it seems off. Hopefully he figured out his issue.