Dowty – Restoration

My Dowty as purchased. Looks OK, but on break down not so good , neither was the trailer

The stern and its antiquated steering nozzle arrangement. Steering cables had no guides through the hull so acted like a saw through the stern

Dowty data – 1958 UK built Turbocraft

Length: 14’6″ (4.42 metres)
Beam: 5’9″ (1.52 metres)
Draught: 9″ (0.27 metre)
Power Unit: Marinised Ford Zephyr MK 11
Propulsion Unit: Dowty-Hamilton Chinook Marine Jet (2 stage)
Maximum Speed (1958): 35 M.P.H. (56 KPH)
Dry Weight: 1 ,350 lbs (612.35 KG)
Fuel Capacity: 10 Imperial Gallons (37.85 Litres)
Seating Capacity: Up to 5

Interior looked OK and was serviceable but not solid and I wanted to use the boat to its maximum

Dowty Engine and Water Jet Restoration

The original engine had a cracked block, so I purchased another and rebuilt it. Right is the result a lovely Ford Zephyr straight 6 – 2500cc engine. The replacement block came from an RAF compressor for starting jet engines

The sequence of the break-down and rebuild at the moment is likely to change as it is a large piece of work.

Engine repair was simple. The water jet dismantling was difficult. Help was found with an excellent Toolmaker friend who manufactured some of the obsolete parts, mostly in stainless steel and aluminium. Below is a large, pictorial file on the strip down and rebuild of the boat with basic details:

Ensure when replacing the cutlass bearing, the correct end is set up for the ‘Leading Edge’, which is marked on the edge.

Dowty jet unit rebuild

A word about the main bearing. This displays the vital importance of setting up the ‘thrust’ spacers. Setting up is the most difficult part of the jet unit assembly. You can see clearly that the bearing has pushed out the side of the inner bearing holder and also a slice in the outer bearing shell. That in turn would chew up the seals, both oil and water.

Assembled drive shaft after full refurbish. Note new sleeve behind 2nd (inner) impeller. The shaft is 1 metre long. There are 9 seals and 1 massive bearing in it, plus a cutlass bearing between the impellers.

Dowty jet unit base plate re-manufacture

Possibly the worst job of all. It required the valuable help of a foundry, toolmaker and a fibreglass expert, large milling machine, specialist alloy welder and of course me.

IMPORTANT NOTE: The base plate has an inherited weakness. The weakest point for leaks and rarely found is at the rear of the intake housing, take a look at ‘Inlet casing’ picture, there is a dark stain below the water exit‘. Pressure of the water being forced out of the exit nozzle causes the seal and even the fibreglass structure to break down. These water-jets produce a considerable amount of pressure.

Dowty Forward/Reverse shift mechanism

Dowty trailer replacement

Dowty Dashboard