We found out by flow testing that boring the 34mm bore to 36mm only increased flow by 1%. The problem is the bore at the throtle plate is 39mm but when you subtract the area of the throttle shaft your back down to 34mm. So, I modified the throttle shafts and can now use all 36mm of the bore. The difference was a gain of almost 200rpm and a new top speed of 91mph.
Modified throttle plates/shafts
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Temp was 91 degrees and very humid.
Broke into the 90's with my 30ET running 90.0 exactly at 7150rpm.
Switched to a prop that LazerEd had given me to try and a fellow member/friend bought. Its a 33 pitch 4 blade cleaver and ran 90.8mph at 7000rpm and was sketchy as all !@$#
It was like riding a skate board on an ice rink. I think I was about 20 degrees sideways at wide open. A 32ET would put me solidly in the low 90's but I would need bigger to go any faster. Bummer because my 30ET is brand new.
The bad news, I broke a new Boysens reed in about 4 miles of 7000 rpm running. Thats my third set in 15 hours. This time the top petals look fine and were all laying flat. Unfortunately I broke the corner off a bottom petal.
My cages will be on the way to Chris Carson Marine in the morning. I am not blaming Boysen as my motor is not really what they were designed for but they are not working for me and CCM reeds always did in the past. I only tried the Boysens since they covered my cut cages (two stage reeds). I never even thought to ask Chris about cutting me a custom single stage set with bigger petals. Maybe Chris can chime in on his thoughts about the reeds.
I may have been able to squeak a little more out of that cleaver but when the reed broke the boat wouldnt even get on plane. I knew what it was right away and as bad as the boat handled with that prop its probably for the better. I just need a solid set of reeds I can use and work on my setup a little more. I think the carbs are dialed in very well and safe now. I will order some reemers to do some fine tuning.
Basically other than reeds and some little setup tweaks, I'm finally there. I dont know of any other 4 cylinder pump gas pleasure boats running in the 90's and thats exactly what I was shooting for. With the ET, the boat is rock solid at those speeds with just a tick of positive trim. One of our members got some video of the 90+ passes today and will hopefully upload them.
Thanks to EVERYONE who helped with this project!
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Originally Posted by John Leeder
