Retired engineer and PBO engine expert Stu Davies
spends as much time as he can aboard his Beneteau
381 which lies in Portugal
ENGINE TALKStu Davies
Reliability
matters!
PBO engine expert Stu Davies enthuses about
the 60-year-old 4-cylinder Perkins diesel
I
n days of old when Yotties were
bold... In 1958 Perkins Engines had
spotted a market for small,
lightweight diesels to be fi tted in
mass produced cars. It was
designated the 4.99, which in the
company’s naming protocol, stood for
4 cylinder and 99 cubic inches capacity.
You can always tell the cylinder number
and size of a Perkins by the model
designation.
It wasn’t long before the prototype was
upgraded to being called a 4.107. This
model had wet cylinder liners, which
basically means that the liners were
sealed in to the cylinder block by O-rings
around them bearing on machined
surfaces in the block. The cooling water
circulated directly against the cylinder
liners to cool them.
However it was found that there weresealing problems with the O-rings and the
engine was upgraded again to become
the 4.108 which were fi tted with pressed in
‘dry’ cylinder liners.
Basically the block is made with
machined cylinders, around which the
cooling water circulates. Then cylinder
liners are machine pressed into thecylinders to provide the bearing surfaces
for the pistons.
So eventually we ended up with a
4-cylinder 108 cubic inch motor – which
equates to 1,770cc. The power depended
on the set-up but usually was between
40-50hp.
The 4.108 found a niche, providing
power for small craft and auxiliary power
for yachts, including Sir Francis
Chichester’s yacht Gipsy Moth III, the
Robert Clark 39-footer that won the fi rst
single-handed transatlantic race in 1960
(not to be confused with Gipsy Moth IV
that circumnavigated the globe).
The engine was compact and it offered
good fuel economy, although the
compactness came at a price. It only had
three main bearings instead of the fi ve
we’re used to nowadays and this could
lead to a certain roughness in operation.Plus the rear oil seal on the crank was a
compressed piece of ‘rope’ which present
day owners still curse! There’s a saying
that if there aren’t any oil leaks from the
engine, there isn’t any oil in it!
However, the engine’s reliability and
economy were prized, as was the
availability of spares and capable
mechanics virtually anywhere in the world.
Part of the availability of spares and
knowledge of how to fi x them came from
the fact that they were fi tted in tractors,
fork lifts etc all over the world. Gen-sets
were a particular niche market and I can
remember in Angola and Saudi Arabia
where I worked in the 1970s, all the
welding sets were driven by 4.108s.
The MOD also prized their ruggedness
and I believe they were still being fi tted to
British desert battle tanks in the 1991 Gulf
War to drive the air conditioning!
Nowadays there are still thousands of
yachts out there fi tted with these engines.
Much chatter can be found on the PBO
forum about renovating them. Spares
were starting to dry up but a fi rm called
Parts4Engines based in Sheffi eld has
taken up the mantle and most parts can
now be sourced there.
A complete overhaul kit can be bought
for £440 including pistons and liners – a
good deal considering the cost of a new
engine! See http://www.parts4engines.com
All in all the Perkins is a great success
story that helped open up the yacht
market to the masses.‘If there aren’t any leaks
from the engine there
isn’t any oil in it!’
They keep on
chugging... a Perkins
4-cylinder dieselComprehensive overhaul kits are now
available for the Perkins dieselparts4 engin
es.com