Double Eagle
Conversion of 3.0L Chivvy to VelvetDrive Inboard
Double Eagle Update 3/24/04 Ken Schott Richmond Hill, Ga.
I started the Double Eagle project with inboard power in mind from the beginning. Fuel economy was a deciding factor in the selection of which particular engine. Modern diesels like Yanmar & Cummins are far better in power/weight ratio than engines of the past, and as such are viable engines for this project. The money factor for a modern diesel keeps them out of my league at this point in time. I thought about a V6 gas and others until I came upon my decided power package. I located a old rotten 'glass hull with a 4-cylinder sterndrive. I bought it for $300. I sold the sterndrive parts and trailer and more than recovered my money.
The 3.0L inboard conversion parts are available from Marine Power, but I desire to be a little more thrifty than their prices. I got a GM 454 bellhousing and VelvetDrive 2:1 transmission on the used market. These mated up nicely with a proper drive damper. Stock flywheel & starter was retained. The inboard mounts were a bit of a challenge. Tranny mounts are the stock Crusader Velvet Drive on rear, self-fabricated on forward.
The forward mounts are 2x3x3/16 steel angle bolted to the block in similar fashion to factory parts. The heavy block was turned on a lathe to receive the 1" shafting mount.
The front drive parts were mostly obtained from
automotive GM parts. The double groove pulleys for water pump and alternator
are both auto parts from various Buick/Chevy/GM boneyards. The double groove
harmonic balancer is a stock 350 Chevy item. All of these pulleys run true to
the belts as they worked out, no shims needed to align the belts. The raw water
pump is a standard marine 
350 Chevy item that goes with the
harmonic balancer. I fabricated the attachment arm to the pump. The wet
manifold is a stock aftermarket marine manifold. The riser is a stock
aftermarket marine item. The carburetor is still stock sterndrive at this time.
I will make determination of the need for a leveling wedge later. Some
rightfully would say that I am ahead of myself by getting the engine first, but
this engine sitting in the garage has served as much inspiration to get the
rest of it moving along. The engine setting on a skid aids in finding the true
center of gravity for placement in the stringers.
Here is a short list of the items for this 3.0L to
inboard conversion.
1. 3.0L block accepts V8 Chevy bellhousing
2. Sterndrive flywheel accepts inboard drive damper
3. VelvetDrive tranny of course accepts stock mounts
4. Fabricated my own front mounts
5. 3.0L crankshaft accepts V8 harmonic balancer
6. V8 harmonic balancer accepts V8 raw water pump
7. 3.0L circulating pump/alternator accepts GM double row pulleys
8. Fabricated raw water pump attach arm
9. Modified alternator adjustment bracket to clear manifold. No welding
required, just heat-n-beat.
10.Carburetor leveling wedge will be determined after sea trials.
11. Total weight has been weighed at 700lbs.
12. Note that a brand new, 2-cycle, 150hp outboard weighs 500lbs. There is a
200lb difference between a cast iron engine with cast iron transmission, and
the outboard. I am disappointed that the outboard couldn't cut the weight
by a full 1/2 the weight. I did weigh my engine, complete at the local truck
stop certified scales.
Also, my complete engine WITH reduction gear is 700lbs. If someone went a little different route, they could very nearly match the weight of a new outboard.
Example: Replace the VelvetDrive reduction gear with aZF/Hurth 45a gear. This alone will save about 100lbs. Replace my aftermarket, generic, manifold with a higher dollar item, save another 40lbs. These 2 items alone are 140lbs saved, and the total difference was 200lbs between the outboard and what I got now. So, I see a final difference of about 60lbs between an outboard and a cast iron 3.0L inboard.
Here is a pic of the harness plate, I forgot about this.
The V8 inboard bellhousing was setup for top mount starter. This left a big hole in the aft side of bellhousing, since I am using the stock 3.0L starter. I fabricated a cover plate, and here I mounted the wire harness connectors and relay.
Since all the Chevy parts are interchangeable so far, I think one could go so far as to get a 14" flywheel, 14" starter, install the top mount starter, wire it up, and have 2 totally redundant starters on this rig. Dual batteries, and dual starters to boot. Now that's a backup for out-at-sea! I ain't tried this yet, but I think it can work if one is so inclined.