Broken prop shaft question?

[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?

[mbrown2]

Another pic

[mbrown2]

Last pic

[Craig]

I've heard of it happening before, but normally you just twist the shaft like this;
http://www.justanothertoy.com/photogallery/boatthumbs/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 :confused:

[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.

[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.

[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.

[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..

[HP350SC]

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

[mbrown2]

Good point!:idea:

[dorC]

When the boat is tipping over is when the prop can really hook up with a lot of engine torque. The shaft will wrap up until it finally twists right off. It's the drivers responsibility to apply the power gingerly. 750hp is not a whole lot, but it is stil beyond the drives capabilites. He should be stepping up to a XR drive. Going to the 1.25 prop shaft will stop the shear, but the problem will now be the vertical shaft or the gears. The broken shafts do occure on cats with only 500hp. The reentry with the high x-dims causes the shafts to flex and fatigue. Again, it's the drivers responsibility to work the throttles.

[Dennis26]

Just got off the phone with Max Machine. They recommended replacing my B1 shaft with their 1" shaft. They said because of the material their shaft is made of, the 1" would still be stronger than an XR 1 1/4". Parts and labor would be about $700-$800, which seems pretty cheap.

[mbrown2]

Originally posted by Dennis26
Just got off the phone with Max Machine. They recommended replacing my B1 shaft with their 1" shaft. They said because of the material their shaft is made of, the 1" would still be stronger than an XR 1 1/4". Parts and labor would be about $700-$800, which seems pretty cheap.
Finally, a little bit of good news..:D

[mbrown2]

Den,
Here is a pic of JRocket's Max Machine Bravo drive...a shaft is a good start:D
http://www.highperformancecars.com/jrocket/2000_dcb_mach26_041.jpg

[HP350SC]

These guys are awesome, real down to earth brothers and they have taken a look at, and improved every single part in the Bravo. I sent just my upper case down(and a check for 12,450!) and they are sending back 1:26 geared complete outdrive with new 2"sportmaster lower with 1" spacer and every upgrade they have, along with WPM dual ram steering. Time will tell how durable their work is, I'm pretty optimistic as my boat is a light tunnel and only 720 hp. They tell me hit it as hard as you want!

[HP350SC]

Originally posted by mbrown2
Den,
Here is a pic of JRocket's Max Machine Bravo drive...a shaft is a good start:D
http://www.highperformancecars.com/jrocket/2000_dcb_mach26_041.jpg
That looks nice!!! Is that WPM steering and are they the longer rams of the two?? My transom is similar to that with the cav. plates and I ordered the longer ones because my pipes are between the gimbal and plate brackets. How old is that drive and how has it held up?

[mbrown2]

HP350, send JRocket a PM, he could give the details on the drive; it is his.

[Tee]

I have also seen that happen when the owner forgets to put the thrust washer on:(

[waterroach]

AARON & JASON ARE GREAT AT MAX MACHINE, BLEW 2 DRIVES BEFORE GOING TO SEE THEM,STARTING MY 3RD SEASON,PUSHING CLOSE TO 950HP ON 24FT HTM.

[HP350SC]

Here's my new drive from Max....

[HP350SC]

Here's the top cap/shower arrangement...

[HP350SC]

and the low water pickup on the sportmaster...

[HP350SC]

Overall I'm happy, but I was disappointed the upper case wasn't painted and their decal/logo wasn't ready yet for the upper case sides.

[Salty Cracker]

What do those drive showers run?? They look trick!

[HP350SC]

They didn't price the shower separately so I don't know. Prolly not too much. Started installing steering tonight, will post some pics. tomorrow.

[mbrown2]

BTW...Dennis26 had to do a little more to drive then a shaft...I will let him provide the details...think there were some gears thrashed..