Crackerbox motor

flabio · Post by **flabio** » Sat Mar 15, 2008 3:20 pm

I am planning on building a crackerbox boat. Before I start I have been putting a material list to help me figure out approximately what it will cost.What size motor is the largest I should use without altering the plans and does the size of the motor change where it is mounted in the boat

Caber-Feidh · Post by **Caber-Feidh** » Sat Mar 15, 2008 8:46 pm

Stick with something in the small block range. length is already a problem to work with, you sure don't want a longer engine to compound the problems. I like GM products best, parts are cheaper. A decent 305 is about the bottom end, but I saw a cracker with an AMC 258 six that was surprisingly quick. For all around easy, cheap build a 350/5.7l is the perfect engine. Weight more than size dictates location from a performance standpoint. Keep the CG within the design and you will be happy. Start pushing it forward and it eats up top end in a hurry.

kens · Post by **kens** » Wed May 14, 2008 8:45 pm

What about this.........
http://www.dougrussell.com/Products/ind ... 6&Brand=70

Scott · Post by **Scott** » Thu May 22, 2008 10:29 pm

Put a Hemi in there and I'll give you a beer and a trophy. What about a Magnum 360 small block?

Time · Post by **Time** » Fri May 23, 2008 1:50 am

I'm using a 2.4L supercharged 252HP ecotec engine. It's only 146kg.

Andrew N · Post by **Andrew N** » Fri May 23, 2008 12:40 pm

Look into a Buick 215 V8. Rare, but light and powerful

Caber-Feidh · Post by **Caber-Feidh** » Fri May 23, 2008 7:11 pm

If you are planning on a build exactly per plans, the chain-coupled drive, and lack of any drive belts is going to hamper any but a small Chev... or (ugh) Ford. For me what draws me to the CB is the overall simplicity, and lack of all but the barest mechanicals.

gwhastie · Post by **gwhastie** » Tue Jun 17, 2008 12:53 am

After 3 years of work, I'm about to flip over my Crackerbox hull and install the local equivalent of a small block Chev (a GM/Holden 308 V8) with a rebuilt Velvet Drive 71C 1:1 hydraulic transmission bolted to the back of it. From the research I've done, having a forward/neutral/reverse transmission affords you the convenience of being able to back away from a river bank/dock or to have full control when manouvering the boat back onto its trailer.

If you use a chain/direct drive, the centre of gravity will be in line with the original Glen-L design ..... with the prop shaft typically driven off the harmonic ballancer end of the engine. Similarly, a dog clutch will also be driven from that end of the engine, but the engine will need to be positioned 6" to 12" forward of the C of G. If you instal a Velvet Drive transmission, the engine will only be approx 12" forward of the chain drive position (plus the transmission is driven off the flywheel end of the engine) and you will need to compensate for the change in C of G by relocating heavy items like the fuel tank and battery forward of the engine or alternatively installing cavitation plates onto the transom (effectively extending the length of the boat to trim it up). One other consideration with installing a Velvet Drive transmission is that if your engine is on a 12 to 14 degree angle, it may protrude further above the deckline than its chain drive equivalent. A good used Velvet Drive 71C 1:1 transmission and a suitable Chevy bellhousing can be purchased on eBay in the US for as little as US$400.00, so its not an expensive piece of equipment.

All that being said, have a look at the Crackerbox that was built by Neil in Toronto (in Customer Photo's section of the Glen-L website). He used a small block Chevy/Velvet Drive combination in his boat. I was so impressed with the drive train and overall appearance of his boat that mine is a direct copy of his.

Regards, Gary H. Melbourne Australia

J Patroni · Post by **J Patroni** » Fri Jun 20, 2008 4:47 am

gwhastie

I also am building the crackerbox and have extended to 16-1/2 feet.
I am using the velvetdrive 71C. But I believe this will create a balance
problem. I looked at 2 Utube video of Neil's boat and noticed in both
that his boat always had a porpose action to it. I never saw it plane off
without the porpose.
For this reason I am choosing to use the 4.3L V-6 MPI at 230 HP.
I hope that this will help keep the balance point as close to the Glen-L design as possible.
The V-6 is 20 HP more than Neil said he got from his 283 cu. in. motor.

tjraisch · Post by **tjraisch** » Tue Mar 01, 2016 5:52 am

gwhastie wrote:After 3 years of work, I'm about to flip over my Crackerbox hull and install the local equivalent of a small block Chev (a GM/Holden 308 V8) with a rebuilt Velvet Drive 71C 1:1 hydraulic transmission bolted to the back of it. From the research I've done, having a forward/neutral/reverse transmission affords you the convenience of being able to back away from a river bank/dock or to have full control when manouvering the boat back onto its trailer.

If you use a chain/direct drive, the centre of gravity will be in line with the original Glen-L design ..... with the prop shaft typically driven off the harmonic ballancer end of the engine. Similarly, a dog clutch will also be driven from that end of the engine, but the engine will need to be positioned 6" to 12" forward of the C of G. If you instal a Velvet Drive transmission, the engine will only be approx 12" forward of the chain drive position (plus the transmission is driven off the flywheel end of the engine) and you will need to compensate for the change in C of G by relocating heavy items like the fuel tank and battery forward of the engine or alternatively installing cavitation plates onto the transom (effectively extending the length of the boat to trim it up). One other consideration with installing a Velvet Drive transmission is that if your engine is on a 12 to 14 degree angle, it may protrude further above the deckline than its chain drive equivalent. A good used Velvet Drive 71C 1:1 transmission and a suitable Chevy bellhousing can be purchased on eBay in the US for as little as US$400.00, so its not an expensive piece of equipment.

All that being said, have a look at the Crackerbox that was built by Neil in Toronto (in Customer Photo's section of the Glen-L website). He used a small block Chevy/Velvet Drive combination in his boat. I was so impressed with the drive train and overall appearance of his boat that mine is a direct copy of his.

Regards, Gary H. Melbourne Australia

Hi Gary H.
How did your cracker box build go with the GM 308?
What was your final degree angle and how did the boat balance go with the 71 C transmission? I'm very interested in starting a build of the crackerbox. Do you have any photos?

Cheers, Tim Perth Australia

fergal butler · Post by **fergal butler** » Wed Mar 02, 2016 12:37 pm

I used a 305 GM and a 71c in mine the 305 is the same as a 5lt Mercruiser so it's handy to get parts for. Have a look at my photos http://boatbuilders.glen-l.com/cracker- ... in-ireland and on my youtube page https://www.youtube.com/channel/UCZg13Y ... bMLUgpRB0w they might be of some help.

slug · Post by **slug** » Wed Mar 02, 2016 6:10 pm

Check around in marinas and with dealers. There are plenty of older dual engine setups with 283 chevys and 71c transmissions kicking around from
older scrap cruisers. Even some of the scrap yards will hold on to them. A friend of mine just told me of two such setups available near me (Ontario, Canada.)
Doug

Glen-L.com

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