Sport 40 Driveline Issue 45 VAC

[Bert Dygert]

I have a GP 400 sport that I have re-powered with a CMB VAC 45 and broke two new 3/16 Hughey shafts. I re-engineered the motor mount to be stiffer thinking that the engine mount was flexing causing the shaft to bind and break. I broke the second shaft yesterday in the second heat . The break occurs right between the motor and the stuffing box tube. The gap is a 1/2 inch of up supported cable.

Is anyone else breaking 3/16 shafts with the VAC motor in there sport 40's?

Do I need to step up to a 1/4 shaft?

The prop was a X646 three blade.

Bert Dygert

 

[NOVALTD]

BERT: HAVE YOU SOLDER THE END. NO HEAT NEEDED. HEAT FATIQUES STRANS ON CABLE. CHECK FOR TO ABRUPT ANGLE

TO THE COLLECT. MUST BE STRIGHT. ALSO CHECK FOR COLLECT AND OR CRANK OUT OF ROUND. IF YOUR 45 IS ONE OF THE NEW HIGH HP 45 LIKE RED HEAD CMB WITH ZIMMERMAN VALVE IS PUTTING OUT MORE HP THEN THE OLD 67S. ALSO YOU MAY HAVE A ALIGNMENT PROBLEM WITH THE BRASS TUBE OFF CENTER LINE OF THE CRANK OFF THE ENGINE. HEAT AND STRESS DEVELOPES AROUND THE OUTLET OF THE BRASS TUBE CAUSING A TWISTING IN THE CABLE. CHECK IT OUT.

HOPE THIS HELPS. DAN MCCORMICK NAMBA 221

 

[shoboat]

Bert,

I think the crank needs to be balanced better than factory specs.

I have heard quite a few are sending them out to be rebalanced.

Thanks,

Mark Sholund

 

[SayMikey]

Have you checked runout at the cable nut? Also did you have enough space between strut and drive dog? Are you sure the shafts are Hughey ive had some cheap ones lately and broke them

 

[Tim Kish]

1/2 inch gap between the collet and stuffing tube ?

Maybe a quick pick will help but if thats the case (probably just reading it wrong) thats a huge gap.

Tim

 

[Mike Betke]

Have you checked runout at the cable nut? Also did you have enough space between strut and drive dog? Are you sure the shafts are Hughey ive had some cheap ones lately and broke them

I think Mike is on to it. Slipped my mind yesterday when I looked at your boat. A bad cable nut will either break the shaft or a crank. With the VAC being such a strong engine your probably breaking the weak link. 1/2 gap should be fine. I have been running that for years with no problem. If you are running a collar on your shaft to keep it from coming out in case it comes loose, make sure that is true as well. I have seen that twist a shaft as well.

 

[Bert Dygert]

Tim,

Here is a picture of the drive line set-up with the CMB HR 45 before a switched to the VAC. I never had a shaft issue with the HR motor.

Most recent set-up picture shown on the right. The bulk head holding the shaft was completely torn from tyhe bottom of the boat.

Hope this helps.

Bert

 

[Bert Dygert]

Mike,

I had a 1/4 of an inch for shaft take up, strut to drive dog.

Bert

 

[anthony_marquart]

I usually have just one that 1x the diameter of the flex shaft for constriction..

 

[Tim Kish]

Looks like a typical setup to me , I figured it would be as you guys know what your doing .

Maybe a bad batch of shafts or as you suggested the motor is just putting out more hp than were use to seeing in a 45.

Tim

 

[Tim Kish]

Looks like a typical setup to me , I figured it would be as you guys know what your doing .

Maybe a bad batch of shafts or as you suggested the motor is just putting out more hp than were use to seeing in a 45.

Was there any sign of heat on the stuffing tube that may have caused the glue to let go ?

Tim

 

[Mike Betke]

Clamp a 3/16 pin up in the cable nut and see how much it is running out.

 

[jim hagan]

If that collar on the stuffing tube was locked down to tight it might be causing the flex shaft to bind up rather than spin freely

 

[Chris Thomas]

Bert, seems to me from looking at the first pic you posted... that the way the outer wire on the shaft is wrapped. It would want to "unwind" when loaded? I am going to look at the twist or wrap in mine later.

 

[Bert Dygert]

Mike,

I'm going to put the motor together tonight and check runout in the morning. Do you remember what thread is on the Hr motor. Time to switch to an Octura hex flex instead of Aeromarine one. Less pieces( two vs. three piece construction).

Bert

 

[Bert Dygert]

Chris,

I caught the right shaft winding at the beginning of the year. That's an old picture.

Good catch though.

Bert

 

[SayMikey]

The Octura is better in my opinion. I went away from them but as of late areo style flexs seem to have a of runout.

 

[Bert Dygert]

Does stuffing box tube diameter matter. I was running 9/32 OD (1/4 inch ID) tubing to 1/4 OD (7/32 ID) thru the strut . Maybe I should run 1/4 OD all the way to the strut?

Bert

 

[anthony_marquart]

I have always used .25 all the way through.. I don't know.. but that may be it.. The shaft I popped a few weeks back was the first in years... since running 12's actually.. I burned up shafts with the .12 riggers

 

[Mike Betke]

Mike,

I'm going to put the motor together tonight and check runout in the morning. Do you remember what thread is on the Hr motor. Time to switch to an Octura hex flex instead of Aeromarine one. Less pieces( two vs. three piece construction).

Bert

Bert,

It should be a 1/4-28 thread. One thing to watch on the Aeromarine is the brass collet. I had one let go on the Nova this year. They can spin with the extra power and do not run true any more. The Octura is usually a safe bet.The other thing is that I run the 9/32 tube as the stuffing tube glued in the hull from behind the hull until it exits out the bottom of the boat. The 1/4" tube runs all the way thru the strut to the front of the 9/32 tube, the entire length. The 7/32 tube should only be the bushing that you run at the strut end and be about 1.75" long. If you are running 7/32 anywhere else in the drive line you could be binding the shaft and causing issues.

I'll give you a call tomorrow. It's been hectic the last couple of days with the housing project.