Z At Sea
By Bjorn ol-of Berglund
The idea to this article popped
up in my head last Easter. The reason is that a month or two earlier I got hold
on two “Z” engines. The seller informed me that they where both marine
converted.
Let’s start with what I
knew, or at least thought I knew. Marine converted car engines where not
unusual in the sixties. Conversions where made at home, or at the local
“blacksmith”, or at a shipyard. They where a bit crude looking, bad performing,
power source. That easily got overheated.
“Oh how wrong a man can be”! Well, to my defence I’ll have to tell you
that there where such mills too.
But why convert an engine in
first place?
To answer that, I will have
to make a qualified guess. In the early days, pre 70´s, if you wanted an
inboard engine with little more power to your daytime cruiser, you had to take
a car engine and modify it. Of course there were marine engines, but they were
either low power or heavy weight engines. So the natural answer was a car
engine.
This is the engine that gave me the idea of this
article.
Note the large oil sump and the up draught
carburettor.
The alternator is a retrofit and was not typical at
the time of conversion.
What does then differ a car
engine from a marine engine?
Well, that’s depends on how
serious you are. First you have the cooling system. You could either have
freshwater cooling, or sea water cooling. The seawater cooling feeds seawater,
via an external pump, straight to the engine. Not particular wise since the
salt tends to eat up the engine from inside.
The fresh water cooling feeds
seawater to a heat exchanger, where seawater cools the engine without mixing it
with the engine coolant. The external cooling pump was driven from an
additional pulley mounted on the crankshaft.
Next question.
Do you run on gasoline or motor petrol? A gasoline engine does not
need any modifications. However the motor petrol was much cheaper than and not
as flammable as gasoline. But since motor petrol has a lower octane rating, it
has to have the compression lowered. Usually by an extra copper headgasket. The
boat also has to have two fuel tanks, one large for motor petrol and one small
for gasoline. A three way valve has to be installed so you can switch between
gas and petrol. The gasoline is used to start the engine, and once it has
warmed up it will be switched to petrol. But you had to remember to switch back
to gasoline, and let it run for a few minutes before turning of the engine, or
else you will have serious trouble the next time you want to start it.
Then you have to remember to cool the exhaust gases. The outlet
from the heat exchanger is connected to the exhaust manifold, and the water is
expelled via the stainless steel exhaust system cooling the exhaust gases at
the same time.
Then you have to have a
large, baffled oil sump. Baffled, to avoid oil pressure loss on a windy day.
1.
Heatexchanger.
2. Inletmanifold
3. Updraught
carburettor.
4. Seawater pump
pulley.
5. Exhaust
manifold
cooler.
6. Exahust pipe
with water
connection.
Missing from the picture is the seawater pump, the
gearbox fitting and the large oil sump
Of course there are a lot to
think of when putting a car engine in a boat.
Usually the spaces you are dealing with are so tight that you have to
come up with solutions that are a bit uncommon. For example, to get a lower
installation, use the updraught carburettor.
But despite the negative reasons to use a car engine at sea, there were several boat builders that used the Zephyr engine. For example the Dowty Marine co in UK used the mk2 6cylinder engine in their waterjet “Dowty Turbocraft”.
DowtyMarine
Waterjet.
Photo
By
Robclem2
Today we have come a bit
from using car engines at sea since there are much suitable alternative to use.
Diesel is a much better option when dealing with water, since there are no
distributors that can malfunction due to moist. And todays gasoline engines use
electronic ignition that is totally sealed.
But our fathers and grandfathers used them with great success, and
I can only salute them.
This old
Swedish ad says:
LIKE
A
PURRING
CAT
FORD ZEPHYR
6 cyl. - 180 kg.
- 80 hp
Cheap – reliable
Easy to
install
For gasoline or kerosene
A less successful conversion. Photos by Ulf Remper.