20V propeller size

[fvanrees]

I have an '05 20V with a Black Scorpion 5.7L engine. Slick boat - love it!

I run the prop fitted by Tige from new and the boat is stock standard.

After 90 hours of use since new (no problems to date), the VelvetDrive suddenly blew a front oil seal. Speaking with a MerCruiser rep, he thinks this may have been caused by the high loads placed on the engine and drive train during wakeboarding (low speed, low engine rpm, high boat drag) which in turn causes high stress/high temperature/slipping of plates in the VelvetDrive and thus seal failure. He suggested we should be wakeboarding at around 4000rpm to help the engine cope. At 4000rpm we will hit 40mph and will have to refuel 3 times a day!

Is the VelvetDrive not able to handle the loads expected of it in a 20V or did the VelvetDrive just suffer an unusual failure and the rest is just a load of rubbish?

Should I be running a finer pitch prop for wakeboarding to increase the engine rpm or just leave it as is?

Have you got any other suggestion why the VelvetDrive seal failed?

[tobo57]

I would call that premature to fail at 90 hrs.I would not change the prop if your happy with the pull.The one thing you could do is run a synthetic fluid .It could be the trans.got overheated for some reason and caused the failier.Overall the velvetdrive is a good trans.

[chpthril]

Does MerC make the VelvetDrive? Sounds like MerC is upset that they are no longer selling engines to Tige! There aint nothing wrong with the prop put on by Tige. I'm sure that ALL the enginers took into consideration the weight, use, load, normal RPM range etc when designing the drivetrain componants, even the prop.

I hope that was a MerC sales Rep somebody needs to step away from the crack pipe.

I would try to get ahold of someone that actualy knows something about the VelvetDrive. Sounds like just a freak seal failure.

Good luck and keep us posted.

[mtnsmith]

I know there have been a couple posts about the trans cooler becoming clogged with debris and overheating. I am not sure how muddy/dirty the water is where you boat but that should be taken into consideration.

[gman]

the question of load on the transmission is a very good one. Has any one at
tige or velvet drive done any calculations to see if the trans is of the proper design and size and is not running at margin and is not overloaded especially with ballast. Question..... how much margin is in the trans?

[whitlock87]

I have the Marin Power 340 hp in my 20 foot v Drive.
(Switch V)
I have the blue gear box ( I believe it reduce the shaft speed )
I am running the stock Prop ( Acme 537 13.5 X 16 four blade with a cup of .105)
We have just under 300 hours with no problem.
We have pulled two wakeboarders at one time , and we have a tow tube that seats 4 ( had over 600lbs in it while slinging it all over )
I personally am a big guy 250 + and I have been pulled over 100 times behind the boat on my Era 147. We are pulling around 2400 RPM’s when I board.

I think you just had a bad seal.
David

[fvanrees]

Thanks

Thanks for the comments.

The Velvet Drive was replaced under warranty with an overhauled unit. No questions asked. Unfortunately this 'new' box failed on the first test run by the boat shop! This box started spitting oil out of the breather. Mercruiser suggested the box had been overheated. Thank goodness the job was done by a Mercruiser dealer! So out with the second box and another was despatched. It took a long time to get this job done but I am grateful to Mercruiser for standing by their product.

It works fine.

No one can suggest any reason for the seal failure. The oil was not burnt and there was plenty of oil in the box. No blockage in the cooling system. All pipes clean. I guess it was just 'one of those things'.

Time for some fun!

Hopefully this new box will be trouble free!