I was looking into this a few years back but never really followed thru with it. I saw a setup before, that I thought was pretty neat. The guy had two pumps. The first pump came on at like 2-3psi, and sprayed in the rear of the blower, on BOTH engines. Then, at full boost, pump #2 came on, spraying in the front of the blowers. I don't know how that worked for him, but seemed like a cool idea.

Alex, how would you compare the cooling effects of water/meth to say an intercooler on a roots blower? I see the car guys seem to be getting some pretty cold IAT temps with meth injection.

I know that backing off the timing will hurt exhaust valves and dont want that. I dont have knock sensors on a tb4 so i cant take timing out that way.
The intercooler is the way to go but getting 3 is a bit much for the odd time when i need gas and there isnt any 92 available for the way home. I dont run wide open when this happens and i try to keep the revs down to avoid boost. Just looking for detonation insurance. Anyone know how much additive is needed to raise octane level from 89 to 92.

Entec racing was a engine shop in scarborough that rebuilds for mercury and i think they do a lot of performance work too. Also, Raymond at Double R on highway 11 north of Barrie has everything a performance boater needs.

Snow performance has a kit claiming to be ideal for blower motors and have the same effect as going from 93 to 116 octane and adding 50-70 hp. Seen it in some magazine i had on the airplane and it caught my attention. I known its a great way to lower temps and add a little power with a diesel but if its everything they say for blown gasser i might have to look into it.

I have used water/alcohol injection a long time ago ('85) on a small non intercooled motor similar to the 525s, we had a 3 gallon tank that was pressurized by the blower (More boost more tank pressure) used a Hobbs switch that closed at 2LBS letting the mixture flow, more boost more liquid to the motor, ran 30* total timing (not Locked) boost ref carbs, and it was pretty much a bullet proof set up as far as detonation was concerned. Inexpensive alternative to a good intercooler, but back then it was the only choice. That being said if one could swing it, I would have to suggest using an intercooler.

A lot of that depends on the size, material, and design of the core, as well as the temperature of the cooling water. An intercooler is a simple way of getting it done for sure, and a good solution for a boat. On an application like the OP though, I might be hesitant to invest that kind of money on the mediocre intercoolers specific to that style blower. If he got the water meth kits set up, the majority of it could transfer over if he upgrades blowers down the road. Having both systems is really the cats azz. You could run primarily on the intercooler and then have the meth come in at a specific manifold air temp to keep things safe. That type of tuning strategy works much better with EFI because you can adjust the target afr and spark to take advantage of the power potential of the water meth mix. With a carb app it is a little more difficult but you still get the safety factor. I have only done a couple of roots setups with it and it worked well, on centrifugal's if you spray pre-blower it will make more boost then without. I would assume running enough through a roots blower would have a similar effect by sealing and cooling the rotors. If you do set up your engine to rely on the water meth, then you better have GOOD safety measure's in place in case you run out of fluid, or have a pump failure/issue. No different really then making sure you have good fuel pressure, but something to consider in the setup. I can show you pictures of what happens when you run out of fluid but don't lift 'cause you're racing your buddy up the river and don't want to lose...

Im gonna be installing IAT gauges on my setup this year. I want to get some baseline temp numbers, and see if any cooling effect would be worth it. I am pretty maxed out on power with my setup from a reliability standpoint, but should still be interesting to see the numbers.

as stated in my earlier reply, tried one from cooling mist, never could get it to flow the correct amount so not to kill RPM, took it off and run it with 2 huge nozzles on my X275 turbo drag car..works awesome there(ls1 25psi on E85, NO intercooler), but if you can fine tune the water flow you can run more boost/timing with it with lower octane...now that we did our own EFI setup on the boat would like to try the meth inj again...