Suzuki DF9.9 conversion to 20HP

[InSaneFisherMan]

I have the 2016 DF9.9BT and have converted to 20HP.

I installed a flame arrester first, and got probably 15HP (17mph) or close, but the engine would go into RPM limiting at WOT.
I then installed an induction tach and found the RPMs slightly high, so changed the prop (increased the pitch). Still had RPM limiting at WOT.
I then replaced the ECU and no RPM limiting at WOT.

Speed increase from 15mph (6000rpm) to 20.4 mph (6320rpm) WOT.

Flame arrester - $15
Induction Tach - $20
9 1/4 X 11 prop - $40
ECU - $285

 

[InCogKneeToe]

Don't forget the Restrictor Plate.

 

[InSaneFisherMan]

Its a restrictor in the 9.9 and flame arrester in the 20hp

 

[DaleH]

I have the 2016 DF9.9BT and have converted to 20HP.

Man, I had to look it up for myself! You just might be onto something here, as per Suzuki's website, they both weight the same and have the same piston displacement, bore and stroke. The LU gear ratio is the same and the only difference in their 'published' specs is the prop of course, and then the MAX operating ranges, but sounds like you identified the ECU as the other difference.

The 9.9hp lists 4,700 - 5,700 RPMs and the 20hp lists 5,300 - 6,300 RPMs. I see the 9.9s selling @ $2,300 new vs the 20s selling @ $3,100 ... hmmmmmmmmmmm. More for electric start and remote operation use, but that includes a side remote control box.

So it appears one can save ~$460 by buying the 9.9hp and doing the conversion as is. Would be useful for places limiting the motor's horsepower, no????????????

 

[wmk0002]

Nice work!

Is that typical cost for the Suzuki 20hp ECU or did you get a deal? Some other motors in that 20-25hp have ECUs that list for over $1000 which makes the conversions very impractical.

 

[PATRIOT2]

FYI . . . my 2019 DF20ATS2 does 25mph GPS for reference, 18 mpg, right out of the box (after break-in) but it was never about speed to start with.

 

[InSaneFisherMan]

Can't speak for prices on other ECUs or for engine models, but the one I purchased for my motor was $285.

I made a mistake in the original post, it was $285, not $265.

Do not order the ECU in the attached clip unless you know it is the correct one for your motor!

 

[InSaneFisherMan]

FYI . . . my 2019 DF20ATS2 does 25mph GPS for reference, 16 mpg, right out of the box (after break-in) but it was never about speed to start with.

My boat is rated for 25Hp, and I wanted a remote with electric start. Two separate boat dealers would not install the 25Hp remote because of the weight. They both would install a tiller without electric start.

The Suzuki dealer had a 9.9Hp remote, electric start, and power tilt on demo, and I got a great deal.

By accident while searching for DF9.9 info, I found that the 9.9, 15, and 20 Hp are basically the same engine.

Did a lot of research and converted mine to 20Hp.

 

[InSaneFisherMan]

Nice work!

Is that typical cost for the Suzuki 20hp ECU or did you get a deal? Some other motors in that 20-25hp have ECUs that list for over $1000 which makes the conversions very impractical.

Can't speak for prices on other ECUs or for engine models, but the one I purchased for my motor was $285.

I made a mistake in the original post, it was $285, not $265.

Do not order the ECU in the attached clip unless you know it is the correct one for your motor!

 

[campbdon]

Can't speak for prices on other ECUs or for engine models, but the one I purchased for my motor was $285.

I made a mistake in the original post, it was $285, not $265.

Do not order the ECU in the attached clip unless you know it is the correct one for your motor!

View attachment 106799

How would you suggest determining the ECU part# to order?. Would it be based on what is installed on a DF20 of the same year and options (ie: elect start, power tilt, remote control, etc) as the 9.9 you want to upgrade?

 

[Still Afloat]

I’ve been looking for a good candidate for this upgrade. Nothing yet at a price that makes it cost effective. Although, it would be really cool to have a 9.9 that runs like a 20.

Based on what I’ve read:
- start with a 2014 or newer DF9.9b
- look at the DF20A in the same year for the ECU and restrictor plate parts

Good luck.

 

[InSaneFisherMan]

How would you suggest determining the ECU part# to order?. Would it be based on what is installed on a DF20 of the same year and options (ie: elect start, power tilt, remote control, etc) as the 9.9 you want to upgrade?

Yes, That is it easiest way, and surest way.

I went with a eailer model ECU for my 2016, because it was a lot cheaper. It took a lot of research to determine it would work on my engine and it was still a gamble.

Also keep in mind warranty issues when changing these parts. Any existing fault codes, break in times, oil change reminders, and engine hours will be stored in the original ECU.

 

[InSaneFisherMan]

I’ve been looking for a good candidate for this upgrade. Nothing yet at a price that makes it cost effective. Although, it would be really cool to have a 9.9 that runs like a 20.

Based on what I’ve read:
- start with a 2014 or newer DF9.9b
- look at the DF20A in the same year for the ECU and restrictor plate parts

Good luck.

Not sure about the year, but the b version for 9.9 is fuel injected.
The engine has to be fuel injected.
The 9.9b has a restrictor plate, the 20a has flame arrestor. So use the flame arrestor.

 

[Still Afloat]

2014 and up

 

[eddieman350]

For $600 you can get a 9.9 flashed to a 20, so the price is very similar without making major hardware changes. Imo a better option

 

[Still Afloat]

An ECM swap or ECM flashing alone will not make this 9.9 a 20. It still needs a different restrictor plate. Also, this is a simple upgrade and it’s easy reversible.

Unless you have a local outfit that will flash the ECM on the outboard, it must be removed, shipped two ways and reinstalled. So a couple of weeks or more downtime for a flash vs 10 minutes for a swap.

Anyway, flashing is certainly an option.

 

[Still Afloat]

For $600 you can get a 9.9 flashed to a 20, so the price is very similar without making major hardware changes. Imo a better option

Who do you use for flashing small outboard ECMs?

 

[Still Afloat]

It ended up buying a DF9.9B that had already been converted to a DF20A. A year later I bought the original ECM and restrictor plate that came off the motor for $100 from the same guy, just in case I ever want use or resell it with the original 9.9 configuration.

The motor runs great and it’s nice to have 20hp with no extra weight. My only regret is not buying a motor with power tilt/trim.