Barrelback-20 Louisville Kentucky

[kens]

You mention you have another engine with velvet drive for sale,
does that have a reduction gear also?

[monitor]

454 Chevy with 1:1 velvet drive.

[Bill Edmundson]

Usually, you can't get more than about 3500 rpm shaft speed before you start getting blade tip cavitation.

Bill

[kens]

454 Chevy with 1:1 velvet drive.

Well there you go,,,, you got it on hand ......
Put the 1:1 VelvetDrive on the 351 Ford.

Sell off the reduction gear and sell off the big block
That 1:1 would likely be the 72 series as well, all the better.
That 72 series 1:1 with the 351 Ford would be baddazz

[monitor]

I still don't understand why I would do all of the switching out of trannys and adaptors etc. (I'm not much of a mechanic) The MC setup worked great in the MC boat. I would think it would work fine in the BB. ( It seems to fit) Even if it were not as efficient in the BB, it would still be plenty of power?
Am I missing something that would keep it from working?

[monitor]

Bill, I'm not sure how the rpm comment applies? Can you explain?

[Bill Edmundson]

Jim

If the prop rpm goes above a certain limit the prop will start to cavitate, create bubbles not move water. If your engine will turn 5000 rpm, but the prop starts slipping at 3500 rpm, that extra power is of no use. The way to get around some of this is a smaller prop diameter with more pitch on the blade. A 14" dia. prop can turn about 3500 rpm. A 12" dia. prop can turn about 4000 rpm. Cavitation will eventually chew up your prop. So, it does have a bearing on HP and reduction.

Bill

[monitor]

Thanks Bill.

[kens]

which model of the mastercraft was that, and how, how much it weigh? (the one the reduction gear come from)
what was length, beam & weight?

[monitor]

1987 tristar
22 foot
6'6" beam
2400lbs best I can tell.
240 hp carburetor model

[psychobilly]

Same one I have in my 240SC

Came standard with a 13” x 3 fluke wheel. I’m running a 14” x 4 fluke now.

That was a rare Tristar BTW and very few had the 454 in them.

[kens]

After watching this thread for week or 2, I seeing a few points that dont add up.
The V8 with reduction gear was said to be 4xx-something lbs. That just cannot be.
MAYBE a V8 long block is 4xx lbs, but not in full marine dress, especially not with a Velvet reduction.
You would do better to figure 1,000lbs for a cast iron V8/VelvetDrive reduction/manifolds/marine dress.

One post said the donor boat was a 22' Mastercraft (ie read fiberglass) that weigh 2200lbs. Again, this cannot be.
I have stripped out several old 'glass hulls and hauled them off to junkyard, stripped out and naked they came out to 100lbs/foot.
Thats 100lbs/foot is just like one of our Glenl hulls at the time we flip them..... Stripped and nothing in them.
For that 22' Mastercraft (ie read fiberglass) it is more like 4,000lbs+ when you put in interior, tanks, systems, engine, et al.

For the V8 reduction gear coming from 'glass hull over to one of the mahoganies (barrelback) , the 1.5:1 VelvetDrive was the only option around back in the day that donor was built. The popularity of ZF/Hurth/down angle trannies was not on the scene as yet. VelvetDrive was cast iron, proven, and indeed bullet proof. Velvet did not have any option less than 1.5:1. The ski forums I have searched as to how they made that work generally come up with a consensus, and that is the 1.5:1 is actually a bit to deep a gear for that boat. Later times they opted for the 1.2:1 available from ZF/Hurth.
The 1.2:1 gear is what Bill and Butch have, and they generally go up about 1" dia. and 3" pitch for that 1.2 gear vs the boats with direct drive.
Enter the 1.5:1 and you would need to go up about 2" dia. and 5" pitch (maybe more) vs the guys with direct drive.

My final opinion is that the reduction gear was marginally too deep in the fiberglass hull, and when you build the Glen-L mahogany you will be shedding 1500lbs from the total weight vs fiberglass. My own opinion is that a 1.5:1 Velvet drive (in a Ford no less) will move from marginally too deep gear to an absolutely too deep a gear.

The Glen-L recommendation is 100rpm (shaft speed) for every 10mph boat speed. This works out well and is proven. I know of a few boats that are geared 60rpm for 10mph. BUT, they are larger boats with smaller engines, thats why it works.
In the original donor boat it had a 15x18 prop, and that was probably a bit small.
When you shed that 1500lbs your reduction gear will be asking for MORE, like 15x22 or more cupping, or more blades, or more of something.

[kens]

THIS, would be a good candidate for a small block V8 with 1.5:1 reduction gear:

https://www.boatdesigns.com/26-or-28-Mi ... ducts/845/

https://www.boatdesigns.com/24-6-Atlant ... ducts/773/

[kens]

Perhaps you should get a survey from Michigan Wheel and Acme.

https://www.miwheel.com/inboard-propell ... -it-right/

https://acmemarine.com/pages/sizing

[monitor]

Thanks guys!
Wow Ken, thats a lot of info. I will need to sift through it and bone up on power plants and boats.
Thanks again.