I have a 2009 27hp Prodrive. I was wondering if anyone has ever changed out their engine for one with more horsepower? And what would be the most horsepower that you can have on that lower unit? I found a 40hp Subaru engine and was wondering if this had been done before and how did it workout.

It's been done with the generac, which i believe is the same motor. Stock carbs, governors, and exhausts sucked, and there isn't much of a market for aftermarket parts. Seemed to be decent motors with a lil work and they were considerably less expensive than a briggs..

36 briggs/vanguard would be the most popular. Not an outstanding platform, but you'll have lots of help with troubleshooting an mods if you need it.

The kawi's seem intersting too. If you aren't in a hurry, you might pay attention to what's going on with those. There is a few guys who've gotten together and are putting them through the ringer right now. Watch the thread about em.

I'd look into the kawasaki like cb said

I did the Generac, like CB said have to change the carb it will not perform without a Mikuni. Exhaust is the only problem have to have one made. Internal parts arent hard to find, just order from Generac. I have flat top pistons and cam from them in mine, its for natural gas motors. I liked it a lot, my complete rig is for sale in the classified section, went to a GT.

Even by modding the Generac it was cheaper than buying a stock Briggs

Ok, I'll try to shed some light on this. Briggs, Generac, Subaru, Kohler. They all have something in common. The oil sump case is bolted to the frame. In the case of a GD, MB, GTR and other small market motors, the engine is bolted to the block. Now this is a big difference. The shocks and hits that the PD goes through puts a lot of stress on these motors. Now you would say the same for the others, but theirs isn't bolted to the sump. Why is this important, because the constant stress put on the sump will eventually cause a crankcase leak at the oil ports or elsewhere.

When Bug (Lee) cracked his briggs block, he was looking for another powerhead of some sort to strap on his frame. Will, Lee and myself got together after they had looked at the design of the Kawasaki. At the present time, the Kawasaki vertical engine is the only engine of its design, currently that we know of. Its crankcase split line is at the top. Thus the engine block bolts directly to the frame. The crankcase top doesn't use a $30-$50 gasket, it uses RVT (basically a gasket type silicon). After looking at drawings, manuals and all sorts of shit, Best of all, the Kawasaki is a direct bolt up to the bolt pattern. The briggs bolt holes are 1/4", the Kawasaki's are 3/8. So its just a matter of drilling out the same existing holes to 3/8. The clutch is the same on the 27 and 36, so in my case (36), it was just a swap out. Now the main reason I bought it was because I didn't want to deal with case leaks. WE had no idea that this engine would produce the kind of power that it is doing. So here is a little breakdown. Jerimiah just bought a Kawasaki. All he did was build and exhaust, and put on a mikuni HSR42, and his hull runs 29-30. This is basically a stock engine, stock heads, and stock cam with just carb and exhaust. Mine is a stage 2 Kawasaki with mikuni 42, cam, headwork and exhaust. Now the biggest difference is that Kawasaki doesn't make performance parts for this. I ported my heads and had my buddys machine shop deck them, I made the exhaust, the cam grind was from Isky in California, the carb from ebay.

We figured that this motor was seriously used in the commercial lawnmower market so we knew is was a great motor, we didn't know at the time that it was gonna be this good. And appears to get better with each additional mod. The price difference is considerable also, its by far cheaper to buy this engine than any other 35, 36, 37 or 40 block. Its also the cheapest to mod of any. I have been told that the Subaru is a workhorse, but after all that, your still back to the basics as far as dealing with case leaks. If you have to change the case leak, you will need an engine hoist, remove the clutch, mounting plate, pull case sump, replace gasket, torque in sequence, and reinstall. A couple hour job. Once the Kawasaki is bolted to the frame, the design of the block has it on the frame and never need to be pulled unless your clutch goes out. Just simple unbolt the top of the cover, and acces all the internal parts without even changing the oil. here is a pic of mine after I installed the cam. To change out the cam on a Kawasaki, takes about 30 min. To change one out on a briggs is several hours. But so far so good. If you went from a kohler 27 to this Kawasaki 37 FX1000, you will be more than happy.
IMG_3161.JPG

Yep, I recommend anyone wanting to or needing to change a Prodrive power head to highly consider the Kawasaki.

Yes you will be happy and I doubt you will remember what a briggs is after running the kawi

So a 27 prodrive can easily be a 37 Kawi ????

Trickiest thing would be figuring out a throttle setup for the stock carb with the tiller handle.

Well if that's the hardest part then it should be a breeze!

I just converted mine to bps throttle lever, had machinist at work make a insert for handle

Just bought kaw for my 27 pd did not want to go with Briggs because of life span of engine. Compression release failures on camshaft plagued the last three I owned. What did you have to do prop wise I had a hard time finding one to work in deep water to start with. This is why I am stepping up motors to step up prop because any more cup and my prop man did not believe the 27 would turn it and perform would kill motor trying to get rpms. Any feedback appreciated.

Do you realize this thread is 2 years old?
Anyway, get a stock, prop for the 36 Prodrive.
It will be good with the kawi

Did you have any problems with the lower unit holding up under more power and are you still running this modified pro drove!

What about drive coupling is it wearing out early with clutch?

Drive coupling? The spline adapter? The lower unit is good for up to 150 hp, gears and all. I don't think a lawnmower engine is going to tear it up. Not if you repeatly hit shit, rocks and stumps with the prop at WFO, then yes you can damage stuff.