XI. The Idea of Remotorization as a Continuation of Life (Overture)
No one knows how it comes to mind. In a particular case, everything turns out to be trivial.
During testing, it is necessary to monitor not only the behaviour of the boat, but also the wake. The wake formed by the boat at speed is good for water skiing: long and gentle, without sharp rises and chop. At wakeboard/surfing speeds, the wave is large and short. The boat lacks propeller thrust. In this case, there is a desire to increase the power of the motor (propeller thrust) and add ballast, but the motor is already at its limit.
The waves are very dense, not loose, which only a boat with a shaft drive can produce.
After analysing these points, it became clear that the hull contours were good and that we needed to learn how to "prepare" them. The stock model also features a classic Vee drive (V drive) transmission system for sports ski tow boats, which allows for excellent weight distribution and increases the cockpit without a "dog house" in the centre and add weight to the stern to strengthen the wake without overloading the boat with ballast, which is ideal for wakeboarding.
A propulsion system is a complex of mechanisms and systems: from obtaining energy from fuel, converting it and transporting it to the end user, in our case, the propeller. Each component of the system is connected to the others and must maintain a certain balance in terms of power and torque. The propulsion system itself is "tied" to the hull, its contours and characteristics. The hull of the boat cannot be separated from the power plant during design.
Our project includes remotorisation. This requires a large amount of work. Important aspects of remotorisation are mass and size characteristics, power and torque characteristics. Coordination with gearboxes and construction of a new shaft line. Each element of the propulsion system must be coordinated with each other and with the boat's hull.
Simply replacing one engine with another... is only possible in one's imagination.
- 4.25 litre (260 CID) V-8 configuration
- Power 120 hp @ 3200 rpm
- Torque 284 Nm (29 kgf*m) @ 2000-2500 rpm
- Bore and stroke: 92 x 80 mm (3.62" x 3.15")
- Centre distance: 123 mm (4.84").
- Compression ratio: 6.7 (7.6):1
- Engine weight: 262 kg
- Aluminium block and heads
- Maximum roll: 15°
- Maximum trim: 10°
By all measurements, this is the smallest Big Block in the world, with a weight comparable to that of cast iron. I will explain these peculiarities in an article about engines.
Let's move on. The engine is aggregated with a coaxial reverse gearbox SSRP-26, which has a transmission ratio of 1.545:1, and an angular gearbox UP-40 with a reduction of 1:1. The weight of the power unit is 401+20 kg.
The torque on the input shaft of the reverse gearbox is 26.3 kgf*m.
The maximum permissible thrust from the propeller, absorbed by the angular transmission bearings, is 400 kgf (3922.66 N).
Counterclockwise rotation propeller. 3 blades. Diameter 335 mm (13.19"), pitch 538 mm (21.18").
Maximum speed of the boat without ballast, without load in the form of a skier with one driver 55 km/h (34 mph) @ 2800 rpm (1812 rpm on the propeller).
Figures after reverse gearbox: 26.3 kgf*m x 1.545 = 40.63 kgf*m (398.4441895 Nm). Propeller speed: 1,456 rpm.
The large propeller pitch is unusual. Unfortunately, there were few powerful engines in the USSR, as well as mass-produced and affordable ones. This propeller pitch allowed the boat to reach its maximum speed. However, it could not reach the skier's slalom speed of 58 km/h in official competitions. For this reason, the factory produced non-standard versions of boats with more powerful engines.
The Borey is the only boat of its kind in the USSR that is officially allowed to have 320 hp under the bonnet, and there is a good reason for that.
According to factory documents, the following engines are conditionally serial engines installed on this boat, in order of increasing power (original engine designations, without marine renaming): ZMZ-53 (M8CHSPU100-1M), ZMZ-13, ZIL-114, Mariner.You can read more about motors on a separate page.
The ZMZ-41 can be installed to replace our ZMZ-53. It is a relative and has the same 5.5-litre displacement as the ZMZ 13, 14 and 505 engines. If the compression ratio is increased, for use with AI-95 MON 85.0 RON 95 petrol (Mid Grade "super" petrol), it is possible to achieve 150-160 hp @4150 rpm and 355-360 Nm @2250 rpm. Looking a bit thin.
Let's move on. The available options are ZMZ-13 and ZMZ-14. The engine capacity is 5.5 litres. And the power after modifications is as much as 195-200 hp. The figures specified in technical literature and brake test reports were obtained using B91/115 (MON 91) aviation petrol, which is always stated in the test reports. When using AI-95 petrol (MON 85.0 RON 95 (Mid Grade "super" Gasoline)), power values of around 150-165 hp can be achieved. Such is the irony.
The advantages of using the ZMZ engine family are that it can be installed as a bolt-on replacement for older models and retains the exhaust-cooled manifolds. It is a classic log-style design without partitions or reflectors and with a small volume. The outlet from the cylinders at a right angle to the manifold is not the best option. The combination of the manifold design and the order of operation of the engine cylinders produces an interesting "choking" effect on one cylinder when another cylinder is exhausting.
The carburettor... with an impressive appetite, consuming 27 litres (7.1 GPH) of fuel per hour. You've described it so well that I don't even want to mess with these archaic designs. And I haven't even mentioned the prices of the engines and their spare parts. The 13 and 14 engines were installed in ancient government limousines. And sellers believe that these are exclusive items that should not be available to ordinary people. The bottom line: why should we install a relic from 1956, when the progenitor of our engine was developed overseas (Chrysler HEMI, 354 CID [331 CID 1951]), at a high price, with high fuel consumption and low power... Let's move on.
Sometimes I had a wicked desire to delve deeply into engine building and get 300-500 hp from an almost stock engine. But this is very difficult. The point is this: if you take/build a factory 53 motor stroker (ZMZ 523), which initially has a volume of 4670 cm3 and a geometry of 82x92 mm, install a Roots-type supercharger on it and get the desired power. There are several reasons why I did not go down this route: it is necessary to manufacture a custom camshaft, install roller tappets and install a supercharger. There would be a problem with air cooling, which means either installing an intercooler under the supercharger or switching to a Lisholm supercharger, which heats the air less, and leaving the intercooler. Don't forget to install a normal ignition system and electronic fuel injection. It can be done, but there are too many custom parts for one project. It will take a lot of time to refine this option.
ZIL 114. More interesting than ZMZ. This is the next stage in the "development of engine manufacturing". Displacement 6960 cm3 (425 CID), power 275 hp @4000 with a decent torque of 559 Nm at 2600-2800 rpm. Aluminium block... Mmm, sounds delicious! But... the price and rarity of the engine, as well as spare parts for an engine from a factory that no longer exists. An exceptional engine for exceptional cases - top party leaders, world-class athletes and experiments. Also - let's move on!
The next option was... a Mariner engine installed at the factory in this boat. So say the legends and documents. In the 1980s, Mariner was the name of... Mercury Marine =)). What was this engine like?
In 1981, MerCruiser did not have any "special" series for tugboats (Volvo Penta did not have any special series either).
In other words, we can "throw in" a Mercury or Volvo Penta and have some fun on the water. It's worth considering.
I think that since we will have to replace the engine mount anyway, we can look at replacing the reverse gearbox from the point of view of modernity: power and efficiency.
The bottom line: there is a Soviet "copy" of an American towboat, which needs to accelerate briskly, displacing a huge amount of water from under itself to create a wave and provide speed for the wakeboarder (15-25 mph (24-40 km/h)). The maximum speed of the boat for towing a skier is also important: 36 mph (57.94 km/h) for slalom and 45 mph (72.42 km/h) for barefooting. At these speeds, the boat planes and leaves only a slight wake behind it. To move such a boat, the engine immediately comes into play: large displacement, high torque from the very bottom of the operating speed range. No turbines. A supercharger is possible. Engine displacement from 5.0 litres and above. Classic V8 petrol or diesel. Only small block in terms of size. I will not consider the use of exotic diesel engines in classic ski boats. Europeans have a very limited choice of large-displacement engines, although the M119 and its successors are attractive but old. The M273 is interesting. Porsche creations are either low-capacity or expensive. Among Asian representatives, there are Toyota engines. But I didn't really want to look for two engine models, and I didn't want to put a Japanese engine in a classic American tow truck either. A replica of an American tow boat should have an American engine.
GM, FORD, and Chrysler have these engines. FORD and GM can be found in marine versions under the Mercury and Volvo Penta brands.
Since we have a solid custom, let's make the engine more interesting from a technical point of view... and history. (Chrysler marine).