Predator 212 Mods - Need advice

#1
Hey guys –
I was hoping folks with more experience could help me think through a few things. I want to build a mud motor for a small boat that I will have to load/unload from a pickup bed by myself, so complete motor weight is key. The boat is rated for up to 10hp but the transom weight restriction won’t allow for the predator 420cc, so I really am stuck with the 212cc. I was hoping some of you could educate me on if I can get ~10hp out of a predator 212cc without having to mill heads, change cams, etc. Also, given that this rig is going to be taking me into some very remote locations reliability and longevity are my biggest concerns.

From what I’ve read, here are the first steps:
1). The mud motor’s prop shaft shouldn’t turn over 4500rpms. From what I have read I can adjust the governor to hit around 4500 rpms without having to remove it. Is this correct? Would I need a billet flywheel at this level?

2). K&N style air intake.

3). Robertson’s torque tube.

4). Rejet carb at around 36-38, 140 emulsion tube. I’ve read the mikuni’s are great but you have to run an inline fuel pump. Not planning on having battery on the boat so the mikuni is out.

5). Upgrade to a decent spark plug, gap at 25.

6). Thinking about 18lb valve springs given floating valve issues but am concerned about this beating up the stock cam and lifters. Anybody have advice/info?

7). Also thinking about the 8 degree timing advance but have heard some folks have had issues with the aftermarket timing keys shearing apart. Anyone have experience with this? Does is even do anything if it is still a stock camshaft?


Has anyone out there done similar mods on this motor and put it on a dyno?
What other beginner mods have I missed?

Thank you for any info and help, yall have some awesome stuff on here.
 
#2
You can adjust the screw on the throttle linkage and raise the governed rpm into the low to mid 4K range. You don’t need to change valve springs for 4500 rpm max operation.
 
#3
You can adjust the screw on the throttle linkage and raise the governed rpm into the low to mid 4K range. You don’t need to change valve springs for 4500 rpm max operation.
Thank you Ole! Appreciate the help. Any ideas on the other stuff? I'm not trying to make 20hp hahaha but would like have a little power.
 
#4
The pipe and jetting will give you a improvement. I dont know what the timing would do but don’t do to many changes at once. if you add the pipe and air filter you will need to slightly enriched it to get the benefit of the better breathing.
 

SAS289

Well-Known Member
#6
If reliability and longevity are your biggest concerns why would you get a 212? I will never do what you are doing but if I did I would be looking at a GX200 or a Champion 196. A Harbor Freight engine would be last on my list of choices.

Have you seen this guys videos and experiences?

 
#7
Valid point - I should have clarified. I know that Predators are a $100 piece of Chinese engineering so there is an inherent risk. My goal is to not make the reliability worse by hot-rodding the crap out of it.

That guy has a bunch of great videos and he continues to use a modified Predator 212.

In terms of my original question, am I on the right track? I seriously appreciate the help and advice. I know all of you have built more of these Predators than I have touched.
 
#8
I run the snot out of my Harbor Freight 212 engines and run them in the desert a very long way from any help and no cell service.
Keep the oil changed and trash the original spark plug as it is total crap.
Add a good in line fuel filter and you'll be fine.
I only run no alcohol added fuel in my engines to protect the aluminum carb parts.
The engine is not modified and runs very strong.
 
#9
i for one would not be going out on my boat too far from my dock with a modified predator. my lake isn't that big but over the years
i have to row back a few times. what kind of boat do you have? what is the prop you are planning on using? i have an 8' john boat with
a 4hp two stroke and an 8x6 prop that pops that little boat out of the water. just picking an engine hp and rpm without knowing your prop
may cause you to end up just cavitating. Are you going to shroud the prop?

who was the member down south who ran mud boats, i would use his mods as he almost always made it home, usually!!!

phil
 
#11
i for one would not be going out on my boat too far from my dock with a modified predator. my lake isn't that big but over the years
i have to row back a few times. what kind of boat do you have? what is the prop you are planning on using? i have an 8' john boat with
a 4hp two stroke and an 8x6 prop that pops that little boat out of the water. just picking an engine hp and rpm without knowing your prop
may cause you to end up just cavitating. Are you going to shroud the prop?

who was the member down south who ran mud boats, i would use his mods as he almost always made it home, usually!!!

phil
Hi Phil-

The prop is 6.5 diameter. Prop wont be shrouded but is aluminum and designed to be the sacrificial component. The boat is basically a 1236 jon boat. Im in south Texas and run saltwater marsh, usually in less than 4 inches of water so a conventional outboard is out for me. If I can push that boat with a small load around 15-18mph I'll be very happy. Not looking for a speed demon hahaha
 
#12
that sounds pretty cool!!! i am running an outboard but i had to make a transom fixture that holds the motor up just a little
and back so i can turn the prop all the way around with hitting the boat.

4" of water isn't much, so you will definitely have all sorts of ventilation, and most definitely a lot of fun!

take a look at single blade props, i've seen some guys use them on shallow draught boats, a single blade cleaved with some
progressive draft seems to work. the scuttle i heard was to place the blade at 90 or 270 degrees relative to a tdc piston for
vibration. that would be two less blades to break!! LOL!!!

phil

this is an 'edited' afterthought: a regular multi blade cleaved prop can run with only one blade in the water and still push.
 
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