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Thread: Broken prop shaft question?

  1. #1
    mbrown2
    I am posting this since Dennis26 has not gotten around to it, but we would like feedback on why this might have occurred...IE: the propshaft twisted and split clean off. Has anybody seen this before, Any info would be appreciated.
    Story goes; Dennis26 was pulling out of Thompson's Bay on Saturday and as he is starting to put the stick down and roll over on plane right outside the bouys , RPM's start shooting up and he loses momentum. Immediately puts the boat in Neutral and checks to see the drive or prop....Prop and part of the prop shaft are missing.
    Boat is a 2002 DCB Mach 26 pushing approximately 725-750 HP....Drive is a stock Bravo 1; 1.5 gears running a Labbed 30" Merc 4 Blade Bravo
    Have you ever seen a shaft twist and shear off as such, and what might cause it? What is the ballpark figure to replace it?
    They did not hit anything, just getting on plane.
    Any info would be appreciated?

  2. #2
    mbrown2
    Another pic

  3. #3
    mbrown2
    Last pic

  4. #4
    Craig
    I've heard of it happening before, but normally you just twist the shaft like this;
    http://www.justanothertoy.com/photog...propshaft2.jpg
    Unfortunately, after this, the upper gears broke (at least that what appears to have happened, it was this past Saturday)
    From what I've heard you twist a prop shaft from either launching the boat and not pulling the throttle back when hitting back into the water. Or...you hit something in the water. Doesn't sound like your friend did either though

  5. #5
    Risky Business
    Just had a friend snap a vertical shaft. Running around 65 mph in his 26 Force with a 540. The shaft just snapped for no good reason. HOWEVER.....He took this 1 year old drive back to IMCO and they are replacing it, free of charge! Kudos to Fred and co.
    Kudos to Charley also, or we may still have the same old IMCO.

  6. #6
    HP350SC
    mbrown2- I think it's fairly common to twist and/or snap propshaft, along with all the other failures. Check out Max Machine Worx in Havasu, these guys have taken the Bravo as far as it can go. Holding up at 900-1000 hp! They are relatively reasonable too, I believe it's around 7K for all their internal upgrades if you use your upper and lower case. My new drive is on its way right now.

  7. #7
    Tinkerer
    That is usually caused when the prop leaves and then reenters the water without the throttle being pulled back.
    That is why You must pull back on the gas when the boat gets air.
    It doesn't take much to twist a prop shaft when you have the HP you have in front of it.

  8. #8
    mbrown2
    Thnx for the feedback....seems strange that it would snap just rolling over on plane...I sent Max Machine Worx and email with pics to get their feedback, but it appears their email addresses are not working; guess we will have to give them a call..

  9. #9
    HP350SC
    Might have twisted it at an earlier time, then finally snapped under load.

  10. #10
    mbrown2
    Good point!:idea:

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