Among our shop's services, we offer cylinder head porting and flow testing for heads and carburetors. We're equipped with a Froude Dyno with computerized data acquisition.
Building power boat engines incorporates circle track and drag racing technology. Power boat racing provides a real test of both torque and horsepower. The most popular engines used in these boats are alcohol and fuel injected 500 CID Chevrolets. Other applications include 494 CID engines with 1071 blowers and G/P Hydro 494 CIDs with 1071 blowers.
Among the engines we build, here we'll focus on the marine race engines that are used in the Pro Stock series. In Canada, this is referred to as the Can-Am series. The U.S. series limits displacement to 500 CID, while the Canadian series allows a 550 CID limit.
A single engine is used in this type of boat, which is normally called a "California ski boat." These boats are 18-20 ft. long, with a flat bottom, and will run about 140 mph in a straight line. These boats, the majority of which are alcohol powered, run a 1 1/4-mile water equivalent of "circle track" events, with speeds up to 140 mph on the straight-aways.
BUILD SUMMARY
We start with the steel Chevy bowtie block and aluminum Brodix cyclinder heads. In order to strengthen the bottom end, we install billet steel main caps from Pro-Gram, which use 4 parallel bolts. Since these are wider than the originals, we have to machine registers for the caps, but this gives us a chance to square-up the cap registers. We stud our blocks, using 7/16" B&B studs on both our head decks as well as for our main caps.
In modifying the oiling system, we bore out all of the oil galleys for optimum flow to the mains. We also increase the size of the oil inlet on the side of the block.
We plug off the oil drain-back holes in the tappet galley to prevent oil from draining directly back onto the crank. We then install #10 fittings at the rear of the block, allowing oil scavenging from the tappet area to the dry sump pump.
The tops of the cylinders are relieved, using a head gasket for a template. We do this in the valve area, basically placing an eyebrow on the intake and exhaust sides, to unshroud the valves. This provides a nice bevel to help entry and exit.
We use Ferrera titanium valves for both intake and exhaust applications. Head sizes are generally 1.880" on exhaust and 2.300" on intakes.
Our rockers are roller-tip Jessel shaft rockers, usually at a 1.7:1 ratio. Some builders may use 1.6:1 rockers on their exhaust valves, but we've had a good success using 1.7:1 rockers at all locations.
The camshafts are billet steel roller cams, usually by Crower. We use a variety of special grinds that we've developed over the years.
We typically use some internal coatings from Polydyne. Our piston skirts are moly coates, and our bearings are coated as well. We tend to leave the piston dome alone, and this is a combination that works well for us., considering the high 14:1 compression ratios we run on our alky motors. Power levels are up considerably in these motors today, and piston scuffing can be a real nightmare. The moly coating helps to prevent this potential problem.
One of the keys to the success of our motors lies with the piston dome shape and the combustion chamber shape. Our proprietary dome shapes and chamber modifications are done to promote flame travel. We have several combinations that work very well, the result of years of experimentation.
The connecting rods are Crower billet steel, usually running their 6.385" rods. We use a variety of bore and stroke combinations, depending on the customer's needs. Probably the most popular combination that we use involves a 4.00" stroke with a 4.40" bore.
As far as piston rings are concerned, we tend to rely on the Total Seal rings, with a fairly tight piston to wall clearance of about .0055", since the Wiseco pistons we use tend to like a tight fit.
A boat engine of this type uses no conventional water pump. Instead, we use a force-fed cooling system that involves an external pickup tube that's mounted at the rear of the boat. At 5 mph or above, water is forced into the pickup tube and fed directly into the fron of the block, at the same entry where the water pump would have been mounted.
Sealing is critical for a force-fed water system, since at speed, hundreds of pounds of pressure can be created. If there's a leak, it'll reveal itself in this type of application.
The engine is mounted with the front of the engine facing the front of the boat, just behind the driver. Instead of using the fly-wheel end of the crank, power takeoff occurs at the snout of the crank. As a result, a special drive flange is keyed onto the snout (a hefty 1/4" key must be fitted to accommodate this). From the drive flange, a drive shaft aims forward, connecting to a geared coupler. From the coupler, a second drive shaft aims rearward to operate the propeller. The coupler gear box allows the team to change drive ratios quickly. This drive system is referred to as a V-drive.
On our in-house Froude dyno, these engines generally produce in the neighborhood of 800-880 hp, at a power band range of 5,000 to 8,400 rpm.
Engine oil of choice for the alcohol motors is a conventional oil with a straight 50W, while we will use a 20/50W in colder weather.
Editor's note: Mickey Marollo Racing Engines currently builds a wide variety of race engines for drag racing, sprrint cars, DIRT modifieds, SuperModified, Winston Cup, super late models, road racing, truck and tractor pulling. NASCAR modifieds, drag mud trucks, and marine racing applications. Their achievements include five-time National Power Boat Championships, four National Power Boat speed records, four-time International Power Boat Championships, sixty track championships, over 160 Power Boat Regatta wins, several GT road racing wins, and six-time New York State truck pulling champions, and thousands of feature wins.
