mattmak wrote:
I don't think I have a really good back to back comparison to take meaningful conclusions from.. Setup has evolved over the past few years, and the 70hp motor I use on the Voodoo is now a different motor than when I first ran it with a large case. (if I remember correctly, prev owner ran a Yamaha drag 14x22, at 55mph. And when I put on a small case and a un-worked Ron Hill semi-cleaver, I saw 55.5mph)
I'd say though that a Yamaha 70hp 2stroke is not a strong 70. I think Tom's Merc Formula Race 60 is stronger (2 or 3mph faster). Not sure how Dok is seeing his speeds (don't know his mods). My 70's are old and stock. Actually, I think Dok's top speed and Tom's are the same?
I'd have no problem saying that an untouhed Yamaha 70 2 stroke (large case) is slower than the top T750 boats. My voodoo with a 1987 70hp and a small case sees 61, maybe 62 on a cold crisp day.. Heavy hooked boat though.
Matt, I have an old and weak stock 70 with a CES style tuner and the choke plates removed on my carbs. My head is cut but it only makes 125ish compression. I also have a CES block but I blew it up the first time out (at Gravenhurst) and I haven't used it since. One day I'll put it back together and we'll see if I can keep it together and get some real compression...still no match for an SST60 but I like my junk lol.
I ran with the 750's in Haliburton and I could out accelerate them from the start but once they got rolling I was done lol. The 3 front runners are faster than me lol. I took it easy at the start because I didn't want to screw with their points but I started trying after half a lap and ended up spinning trying to keep up...
I ran the big case on my Delta (Paul's) and I think it was close to 60 with one of Don's props...I didn't have that combo for long.
Tom's 60 is for real in terms of top end but it's definitely harder to get settled and acceleration is a bit off due to the weight (of both the boat and the motor likely).