Water injection questions from the Quincy Forum

[iwanajohnson]

alright guys, relatively new to high performance outboards. I was wondering if anyone woudl take the time to help out someone like me. I don't think It will be a problem because everyone on this site is extremely nice and helpful nomater what your boating experience that's Why I love this site so much. I was wondering if anyone could explane to me this water injection and how it worked. I've personally never heard of it but had kind of been thinking about something similar. I was thinking If I could test the weight vs. gain ratio, somehow get a tank of iced down or cold water and put in the boat, that way it would be able to be circulated around the engine to keep it cooler. was wondering if this would impact me in any way as far as positive or negative. I'm primarily goning to be drag racing so It's all about 1280ft. could someone tell me about this water injection and tell me if my idea's off or anygood. Also I deal with only 2 & 3 hold OMC motors, maily the 56ci tripple. was wondering if anyone had ever thought of filling in the spark holes on a tripple, having it drilled and threaded for 2 plugs, and running 6 spark plugs on a tripple with 6 coils, a mod 50 front and wicked port and exhaust work done. am I crazy or a genius. someone help me out.

[Mark75H]

Water injection is pretty simple. In a tuned pipe the length of the pipe AND the speed of the sound waves are critically designed and built for a specific motor RPM. The pipe only increases power in a narrow rpm range ... maybe 1 thousand rpm on either side of the optimum. So if the pipe is built to give best increase power at 7,000, it works somewhat at 6,000 and 8,000, but is usless at 5,000 and 10,000 rpms. 10,000 rpm probably doesn't matter that much, but going thru the turns, the motor rpm probably does go to 5,000 or lower. Two things can be done to make the pipe work at lower rpm, the pipe can be longer .... or you can cool the exhaust down and slow down the sound wave to make the pipe work at a lower rpm.

Variable length expansion chambers are very popular on racing outboards, water injection is less popular, but has been used. Variable length is harder to set up on megaphone tuned exhaust, so water injection is usually tried instead on megaphones.