
My Dowty as purchased. Looks OK, but on break down not so good , neither was the trailer
Before you embark on a restoration of a boat, do not think it is as easy as a classic car. Many items are often unique to the craft and can be unobtainable within about 10 years. Nearly all parts will fight you to remove them or break. Nuts and bolt are always difficult, but often ‘automatic gear oil’ will help. You will also require a lot of skills or people to assist in the re manufacture of parts.
This documentary of my Dowty was possibly one of the most difficult and complex to do. It required skills from Toolmakers to a Casting Foundry. From a windscreen maker to an upholsterer. From a carpenter to a F1 fibreglass specialist and many more. To all the people who assisted I extend my gratitude and thanks.
My Dowty Turbocraft
I purchased my Dowty Turbocraft in 2010 a 1958 MK1 (14’ 6” test boat apparently). It looked OK on the outside, but revealed a series of monster problems on strip down, a full rebuild was required, plus a donor boat for the obsolete parts and a new trailer.
The hull was solid, but damaged with general use, however all the mechanicals were in a real mess, with corrosion and broken bearings, seized up controls and the jet unit was rubbished. All this can be seen in the Dowty restoration section.
As in many marinised car engines it was not good, with a cracked block repaired with fibreglass filler. The engine cooling was clearly in a big mess. Oil cooling was a primitive 15mm copper pipe in the sump which had burst, which of course diluted the oil and blew it out into the water.
The engine was sea water cooled via a take-off from the jet outlet and flow could only be regulated by a gate valve. Flow is dependent on engine revs and water from the pressure inside the jet casing. There was no water pump or thermostat, so cooling water flow rate was erratic and engine temperature impossible to manage. Also, the iron castings in the engine block and cylinder head were subject to corrosion, as was everything else on the engine. These poor engine cooling arrangements caused many engine overheats in Dowty’s, so the temperature gauge is vital. A full rebuild was required and new engine block was required. The exhaust manifold was OK.
The through transom exhaust is silent at slow speeds when submersed, then rather pleasant when the engine note can be heard when on the plane. The sealed double row ball thrust bearing and the water lubricated cutlass bearing supporting the impeller shaft were both completely trashed, possibly due to sand and flint being drawn up by the jet at the cutlass bearing end. The large bearing even had the sides knocked out (can be seen in Dowty restoration section). The original stainless steel impellers were fine.
The hull and deck were structurally sound, but cosmetically poor. Marks and surface damage on the hull were made good, by a professional. The interior trim panels were replaced because they were smelly and rotten. A new curved and bowed windscreen was made and fitted at a cost, plus a new dashboard.
Driving a jet boat is an acquired skill, so the foot throttle had to be repaired correctly. The Dowty Turbocraft is different for sure, but fun especially when a 360 turn can be done at top speed, let alone the shallow water running, but the Dowty Turbocraft is not without its quirks for sure.

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:
Replacement engine Not too bad Dowty Manifold Engine rebuilt New wiring Electronic distributor Nicely hidden electronic internals Activation tube-note washers at stern, these should be 1/2 moon bands Wierd steering Jet outlet Reduction nozzle Steering flaps Reverse guile (left broken) Right new one Steering, reverse & exit nozzle Reverse rollers outer impeller Impeller blade – stainless Activation tube – stainless Straightener blades Cutlass bearing shim between blades Inner blade Warer leak area Activation tube removed – reverse link above Rats evicted Jet base plate removed Serious leak under base plate Engine support Engine support Drive shaft coupling Removing coupling Massive chunk out of main bearing Bearing pot – hard to remove Lead telltale inserts to indicate removal Old seals Prop with seal holder sleeve Cuts in prop tube from seal Spacer and cutlass bearing sleeve Removing cutlass bearing

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

Not a good idea to stop a leak. This was someones idea to stop water ingress. It was not even at this point, but at the stern. The pictures above also show the main leak area.
Dowty jet unit rebuild
New & old cutlass bearing converted barge steering bush Cutlass bearing ready for fitting into activation unit Fitted-ensure you read the edge for the correct end 1st impeller fitted 2nd impeller fitted Intake housing ready for assembly Bearing pot and cover Bearing pot Bearing pot parts Bearing pot and seals placed in following Seal fitting sequence Bearing with drive sleeve Bearing pot housing-note marker to see if been off before Seal ready for cover Loose assy waiting drive coupling, then respray whole unit

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.
Old jet intake base plate extracted from hull, very difficult job Tried welding torn threads-no good So new cast alloy base plate cast-bigger-thicker-stronger-harder alloy Inserts top-bottom to increase performance and reduce leaks. Drilling and tapping of holes was a chore, due to the accuracy required Easy job-new gasket 3mm synth cork New base plate inserted-dreadful job required F1 fibreglass specialists help Test fit-looking good Original exit and steering for jet Having a bit of fun (all returnable to original) fitting a large jet-ski nozzle and bucket for better power output, reverse and steering control New engine frame New dashboard, trial fit much more to do. More to come on all these items.
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
Gear box for reverse-forward Start of disassembly Oil bath and helical gears Shift box F/R shift bearing front end Huge shift shaft 12 foot F/R shift stern Bottom of shift box F/R slots in shift box
Dowty trailer replacement
Original Trailer-Not Good New wheels,axle & suspension I have started new trailer Little extras added Upgraded chassis More little extras Done and galvanised – temp mudguards
Dowty Dashboard
Old plastic dash Marking out new dash for gauges Trial gauge and switch fit Gauge and switch fitting after powder coat
MUCH MORE TO COME WITH THE REBUILD OF THE BOAT-IT IS JUST FINDING THE TIME AND RIGHT PICTURES FOR YOU