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 InteriorEngine ChangeOther boating photos
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