Seamaster 25 - Admiral - Fitting a new 900cc 3
cylinder diesel
Our Seamaster came with a 30 year old 1500 cc Ford Watermotor which was a
pre-crossflow Ford petrol engine from the old Ford Anglia or Mark 1 Cortina.  The day
we collected Kimbo 111 we motored to our new Marina birth only to find a fire engine  
putting out a blaze on the boat 3 moorings down.  This was a Freeman 21 fitted with
the same Watermotor which had caught fire while warming up.  Petrol fumes collect in a
boat hull with potentially disastrous results.
Our motor ran well but it was very difficult to start, classic signs of a worn out cylinder
bore and resulting low compression.  I decided to fit a small diesel engine and I chose a
900cc 3 cylinder diesel from Thorneycroft.  This cost around £3,000 with gearbox and
control panel.  Not too bad as a diesel powered boat is worth at least at least £3,000
more than a petrol.
I transplanted the engine over Christmas 2002, it was freezing and both the engines
were very heavy so I hired an extended forklift.  I then had to fit a bigger propeller with
a course pitch.  I was worried that an 11BHP diesel would not push the boat along as
well as a 25 BHP petrol.  Everyone had reassured me it would be OK.  In practice the
little Thorneycroft was perfect.  I could maintain 2.8 knots on tickover, 4 mph on very
little throttle and 12 mph flat out which was the same top speed as the Ford engine.  
The river Ouse is restricted to no more than 7 mph at best and 4mph on many
stretches.  Our little diesel had no problem coping with long runs upstream against the
current.  A really rewarding project.  The Thorneycroft used about 1 gallon of untaxed
red diesel a day, about 40p,  which was a bonus.
New control panel
New 12 x 14  propeller fitted.
Removing the old one from the tapered shaft was very difficult because I
could not remove the rudder.
New engine box in the cockpit. My first attempt at routing and working with wood stain
Mahogany Interior
Engine Change
Other boating photos
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