Prop slipping

[motocross269]

I have a Bass Cat Jag..225 Vindicator motor..25P prop (Turbo OT4) 14.25 dia According to my measurement the Motor Height is 3.5 inches..Don't ask me top speed RPM numbers I haven't gotten there yet... But seems to be about 5000 around 60-65 MPH..
When I come up on Plane my Prop slips Badly..It doesn't do it right out of the hole, but seems to slip when the boat starts to level...It did the same thing, but not quite as bad when I had my 27p Raker...Should I try to lower my motor a quarter of an inch...? How much of a difference would that make?? How low can you get away with lowering a motor without getting into problems in other areas of drivability...Thanks...B

[SethV]

When the bow breaks over on pad and you start to slip, have you started to trim out or are you still tucked in all the way?

For that rig, 3.5 sounds about right, but you can try to drop the motor a little.  Worst case you will give up a tad bit of speed and it may want to chine walk a bit easier with the motor lower.  On the up side, you will have better grip, which we tend to need in the big water anyway.

Seth

[dmills4124]

If you adjust the trim and jack plate and you still have the same problem you have spun your prop. You can spin a prop without hitting anything with it, I did. These "new" props don't have a shear pin anymore. The prop has a vulcanized rubber center designed to break loose instead of damaging the lower unit. This happened to me last year on my high speed stainless steel performance prop. Your looking at a $100 bill to fix it. But thats better than $300 or $400 for a new one. Trouble is you will be down a week waiting for it to come back. I would really try the adjustments first.
good luck
don m

[motocross269]

It has a brand new flo-torque hub in it and it is a new prop..I don't think it is the hub or it would slip right out of the hole not just when it comes over the top....I would think...
When it starts to slip I am still tucked in all the way and haven't started to trim up....I have been waiting for the boat to get flat before I start to trim...

[SethV]

It has a brand new flo-torque hub in it and it is a new prop..I don't think it is the hub or it would slip right out of the hole not just when it comes over the top....I would think...
When it starts to slip I am still tucked in all the way and haven't started to trim up....I have been waiting for the boat to get flat before I start to trim...

You are gonna get some slip there, but it sounds like you have more than the normal slip.  Try dropping that motor a tad.  I know when I launch in shallow water with my plate way up it slips like crazy.  Go to 4" below and see what it does.

Don-  the new hubs are an insert, so no more gluing hubs in.  You can't just slightly spin one.  You spin it, you won't get the boat on pad.  On my ProXS, it does not even have the plastic insert, no hub to spin.

Seth

[smbassman]

Unfortunately, the Hydro props don't have the PVS system to help in this adjustment.  You are going to have to bury the prop.  Like Seth said 4"es should help, but don't try to get rid of all the cavitation.  You want it to break free some as the nose drops when you have a normal to light load and in cooler temps.  Just get used to feathering the throttle.  Then when you are loaded down with full fuel, livewells, 90 degree air temp and a 300# partner, you will still have some ventilation to get out of the hole.

With the prop that low, you can expect it to be harder to handle at the top end (it doesn't sound like you have been there yet) and if you have cable steering, there will be significantly more steering torque.

Let me know if you still want to try my Trophy prop.  I can bring my spare this weekend.
Jarrod

[Revtro]

Brian,
Though it sounds like you're getting more slip than normal, it's not all that unusual to start to slip as you come up on pad.  Mine is somewhat similar.  I just start to back the throttle off a little as it planes out, then step on it again.  I could reduce venting, and not have to feather the throttle at all, but then I'd lose hole shot.  So it's worth the trade off if you're jumping on plane quickly IMO.

PS.  This is where a Hot Foot really helps.   

[motocross269]

Thanks for all of the good info...I may send my Prop out to Mark Croxton and have him put PVS holes in it..I guess he works wonders with these props..I put a small ding in it this past weekend anyway. 

[Revtro]

Bri, one thing... that might not be a good idea.  Vents: Larger holes equals more air coming across the blades equaling more slip, not less.  On a Trophy, for instance, you make the holes smaller to reduce slip.  So adding holes will not reduce slip if you already have slip, unless maybe you plug the holes altogether. 

But if this is for a prop that's not slipping, but you want a little more RPM on the hole shot, adding PVS vents will help, but you'll need to experiment with different size plugs. 

[Skulley]

There is a very informative article on this subject in the July 2008 issue of "Go Boating" magazine.  It has the mathematical formula on how to figure out what the slippage is on any boat.  Very educational and informative.

BD