Really hot dipstick

[Roxylass]

Came in from fishing yesterday

Lifted the engine box lid as I saw

Some light smoke engine hotter than its ever been SR2 cut out when I put it down to tick over let it cool down and pulled the dipstick showing correctly on the dipstick mark had latex gloves on

The last inch of the dipstick actually

 Burnt my fingers

The oil looks good no smell of diesel

There is a film of oil on the exhaust manifold

Puzzled

[Yellowback]

You fishing on the local duckpond, or thrashing the engine to within an inch of its life fighting against a rising tide with an oversize beam trawl in tow ?

[Roxylass]

Half throttle

4 miles out 4 miles back in

[Tony Brooks]

The TV implied it was very hot your way yesterday, so if it's air cooled are you sure there is adequate air ducting for the cooling air?  The oil normally plays a big part in cooling the pistons and I doubt that you have an engine oil cooler, so with poor or no airflow around the crankcase to cool it, I would expect hotter than normal oil it elevated ambient temperatures. Engine oil temperatures can go well over 100C in engines. Indeed they should to boil out any condensation, otherwise the oil can turn itself into a greasy type substance.

[Roxylass]

Half throttle

4 miles out 4 miles back in

[Tony Brooks]

2 minutes ago, Roxylass said:

Half throttle

4 miles out 4 miles back in

 

?

 

If the ambient temperature was as hot as the TV suggested, then the oil will be hotter than at a lower temperature. I note you don't address the cooling duct adequacy.

[Roxylass]

The fan in front of the gear box

Also a 9inch x 6inch cut out

On the engine box port side

[Tony Brooks]

So is that an open slatted or solid box?

 

Is the cooling exhaust air ducted to the 9 x 6 cutout, and if so how does the cool air get into the fan?

[nicknorman]

23 minutes ago, Roxylass said:

Half throttle

4 miles out 4 miles back in

Bear in mind that the “throttle” isn’t really a throttle, it is an rpm selector for the governor. The governor will send in as much fuel as necessary to achieve the set rpm. So for example if the prop had some rubbish on it that created a lot of drag, the governor might be sending in nearly maximum fuel to achieve a middling rpm, and thus a lot more heat is created.

Edited July 26, 2021 by nicknorman

[Tony Brooks]

Even without muck on the prop, if the cooling is inadequate the engine may well overheat and partially seize, so doing what Nick describes. The failure to idle tends to suggest a stiff engine.

[Roxylass]

Half inch plywood engine box

Only outlet is the one I described

As far as I knew the fan sucked

Cold air in circulated the engine

Any air coming from the exhaust

I would have thought to be far to hot

[nicknorman]

All the lister aircooled installations I’ve seen have an inlet grill and an outlet grill. If there is just one grill then it’s hard to see how there can be adequate cooling. It sound as though this is a sea going boat so obviously engine venting is a bit more complex than for a canal boat (need to keep the sea out!) but I think you need to consider the entire airflow path from outside to outside, via the engine/fan.

[Arthur Marshall]

When did you last change the oil?

My Lister cuts out when it overheats, usually due to disel contamination in the oil  but also if the oil is so old it's stopped working.

Before I corrected the ducting for the hot air eject  it also used to overheat in very hot weather as not enough cool air got in and I had to drive with a deck board up - still didn't like last week much.

If the cutout for the air is the only one, is there any ducting at all?

(Crossed with Tony's below)

Edited July 26, 2021 by Arthur Marshall

[Tony Brooks]

17 minutes ago, Roxylass said:

Half inch plywood engine box

Only outlet is the one I described

As far as I knew the fan sucked

Cold air in circulated the engine

Any air coming from the exhaust

I would have thought to be far to hot

 

OK, so do you understand air cooling. The COOLING system needs cool air delivered to the fan and the DUCTS to direct that hot air away to outside the engine case. Without the ducting, the fan will just recirculate the hot air back through the cooling fins so you get exactly what you found. The ducting must not leak hot air into the engine bay. The Lister marine manual explains all this.

 

In fact, experience tells me it is also a good idea to duct air from outside the case direct to the inlet manifold.

 

The engine exhaust pipe has nothing to do with the cooling air exhaust.

 

Luckily for you those engines are very robust plus some, so if you sort out the COOLING EXHAUST AIR ducting and vent it is unlikely to have suffered from the partial seizure.

 

Edited July 26, 2021 by Tony Brooks

[Roxylass]

Tony

I shall take some photos of inside the box today you will see a clearer picture of what I am trying to explain

Your help is appreciated as always

[Tony Brooks]

It is simple. Your cooling "fan" is part of the flywheel and as such without an expensive custom-made cowel to fit around it with a spigot to connect to a cool air inlet duct it's best to just let it suck COOL air out of the engine bay. But to do this it needs an easy access for the air into the engine bay. This is where your 9 x 6 hole comes in to use.

 

The "fan" blows the cool air into the air casing around the engine, through baffle plates that ensure  an equal amount of air is blown through the fins on each cylinder. That air gets hot as it cools the cylinders.

 

The hot air should exit the air casing via another thin metal shroud that allows you to connect large air ducts to the connected that then run to  another hole or holes in your engine case. Preferably on the opposite side to the inlet hole.

 

Thus, the hot air exiting the engine cooling system is kept well away from the cool air being drawn into the case or being recirculated through the cooling system.

 

You need two large holes in the case unless the case is slatted all around as per the Lister specs. One to let cool air into the engine case and one to allow ducted hot air to exit the case. If you don't do that you WILL be subject to partial or a full engine seizure and if the SR has steel inserts in the pistons like the SLs a steel insert might pop out and jamb the engine. Possibly bending valves, push rods and/or the connecting rod. I think (but don't know for sure) that the SR does not have such inserts.

 

[Machpoint005]

2 hours ago, nicknorman said:

All the lister aircooled installations I’ve seen have an inlet grill and an outlet grill.<<

 

Without a fresh air inlet and an air discharge, the hot air will be going round and round and round the engine compartment - and the heat doesn't get lost. That applies to any air-cooled engine. The amount of cooling air required is a great deal more than the engine's combustion air requirements.

 

This applies to any air-cooled diesel, not just marine ones.

 

 

 

 

Edited July 26, 2021 by Machpoint005

[Roxylass]

Arthur

Do you have any photos of your engines ducting could be helpful

Other wise going to have to cut slots

In the front of the box and enlarge

The holes I already have can't see how I would be able to fit ducting in that box

[David Mack]

This is a ST2, similar to your SR2. 

Cooling air is drawn in through the grill between the engine and gearbox in the centre of the photo, and the hot air leaves the engine via the red metal duct and into the canvas trunking. You should have something similar to the red duct leading directly to the outside of the engine case.

[Tony Brooks]

Here is the manuallstrsrm.pdf

 

Pages 6 to 8

 

[Roxylass]

Very similar indeed

I will see where I can get a canvas

Trunking

[Arthur Marshall]

I used a bit of central heating ducting with a face plate on the original box, which had canvas ducting originally. With a cruiser deck, the canvas got wet and sagged and stopped chucking the air out. When I bought the boat, it had obviously caught fire at some stage too! Pics aren't very good as access is tricky.

 

[Tony Brooks]

I think the plate your two ducts are fitted to is/was a Lister part, except I have seen the crimped aluminium ducts used in place of your plastic ones. My guess is that the OP does not that the adaptor needed to fit either the ally, plastic or canvas ducts.

[Yellowback]

8 minutes ago, Tony Brooks said:

My guess is that the OP does not that the adaptor needed to fit either the ally, plastic or canvas ducts.

But I'd bet she's capable of fettling something suitable now she's seen what's needed.

[Tony Brooks]

16 minutes ago, Yellowback said:

But I'd bet she's capable of fettling something suitable now she's seen what's needed.

I think the gender you assume is from the boat name, the OP gives his sex as male.