Tohatsu 9.9 to 20hp

rocksteady1

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So i currently own a tohatsu 9.9 and want to get a little more firepower out of it. Ive heard that the 9.9,the 15 and the 20 are basically the exact same engine with different ECU's and a restrictive plate on the smaller two. Has anyone ever done this swap or heard of this? Thanks in advance.
 

tucker99

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I just took delivery of a MFS 20E EFTS. Not sure where the restrictor plate is. Yea, it seems to be the exact same engine. I'd make a post over at Marine Engine on the Nissan Tohatsu forums. There's a Tohatsu tech that answers most questions and seems to be very good. Be sure you give the complete model and serial number of your engine.
 

DaleH

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Use the search feature guys ... as the parts needed are well documented here!
 

blackshear

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I converted my 9.9 EFI to a 20 with a new module and removing the restrictor plate. I also had to buy a different prop because I was turning to many RPMS. The 9.9, 15 and 20 come with different props from the factory so running a stock 9.9 prop on a 20 would not be recommended unless you have a heavy boat. The addition of a Tiny Tach tachometer will make sure you are operating in the normal RPM range. I haven't had any issues with my motor so far and the difference in performance is huge.
 

DaleH

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crappie777 said:
Looks like a new prop and a new module is all that's needed. Just for kicks and giggles, what's a new module going to cost you?
Wrong ... as you need to also remove the restrictor plate/flame arrestor and replace it with a new one like the 20hp wears.
 

blackshear

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DaleH said:
crappie777 said:
Looks like a new prop and a new module is all that's needed. Just for kicks and giggles, what's a new module going to cost you?
Wrong ... as you need to also remove the restrictor plate/flame arrestor and replace it with a new one like the 20hp wears.

Are you sure there is a restrictor plate for the 20? I watched the mechanic remove mine and I don't remember him putting one back in. That doesn't mean there isn't one for the 20 and if it does require a plate I need to see about getting one.
 

DaleH

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Look at the schematics (Www.marineengine.com or other sites) between carb & inlet manifold, I believe there is some nozzle that will not be there if you have the 9.9hp. Besides, the guy here that has done has said one needs to replace the restrictor w/ the flame arrestor or whatever they call it.
 

rocksteady1

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Word around the campfire is u need to remove the restrict plate and change the computer. According to Tohatsu themselves that’s it. They weren’t even really reluctant to tell me. They said it did void the warranty and that the EPA wouldn’t be happy but that it was relatively easy to do.
 

InSaneFisherMan

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All gasoline engines installed in a vessel, except outboard engines, must be equipped with an acceptable means of backfire flame control.

Even though there is no cost guard requirement for outboards, if the manufactures makes a backfire flame arrester, its probably a smart and safe idea to install it.

Just my 2 cents!
 

PurvySage

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blackshear said:
I converted my 9.9 EFI to a 20 with a new module and removing the restrictor plate. I also had to buy a different prop because I was turning to many RPMS. The 9.9, 15 and 20 come with different props from the factory so running a stock 9.9 prop on a 20 would not be recommended unless you have a heavy boat. The addition of a Tiny Tach tachometer will make sure you are operating in the normal RPM range. I haven't had any issues with my motor so far and the difference in performance is huge.


You got more information (pics? pointers?) before I invest in this? Lol. There are hardly any videos for the 2022 efi 9.9, let alone this topic. Anything would be appreciated.
 

hollandcrew

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All you need is the 20hp ECU ($600) & remove restrictor plate. In my case I need a new prop the 9.9 came with a 9 pitch probably need a 10 or 11 pitch now to get the rpm's down within operating range. There is a huge difference once converted. Easy job takes about 30 minutes.
 
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