Thornycroft T90 decompression lever

M

miracze

New Member
Joined
26 Dec 2021
Messages
13
Visit site
Hi,

I can't locate decompression lever on my Thornycroft T90. Could anybody please point me to the right location?
 
superheat6k said:
Doo you know what the source engine is ? All Thornycroft are a marination of someone else's engine. They never made their own.
Click to expand...
ThorMycroft pruducded many engines of their own rright but wtth the merging etc the moved ovr to naturally BMC units keep them on a single single supplier t90 was BMC 1500
sorry this is near garbage so I will have another go
Thonycroft built a long line of their own engines the handbilly was possiblely the best known a 2 cyl petrol engine
Donald Stokes was given the job of sorting out the collection of companies that became BMC which included Thornycroft and at that point they maid use of the BMC 1500 referred to as the T90
bonus point for knowing that the Mighty Antar tank transporter was one of many large commercial vehicles produced by Thonycroft.
 
Last edited:
I think you can't find one because there is not one. It is a BMC 1500 B series base engine as used in various BMC commercial vehicles in the 1960-1980s. Road vehicle engines do not have decompression levers - in fact few marine engines do except those that are designed to be started by hand as well as electric starter.
 
Tranona said:
I think you can't find one because there is not one. It is a BMC 1500 B series base engine as used in various BMC commercial vehicles in the 1960-1980s. Road vehicle engines do not have decompression levers - in fact few marine engines do except those that are designed to be started by hand as well as electric starter.
Click to expand...
Hi,

thanks for answer. So only way to manually spin the engine is to take out the injectors? I've suspicion of waterlock due to bad winterisation so I don't want it crank "normally" because of possible damage.
 
The waterlock is downstream of the engine so you can shut off the water intake and turn the engine over with the starter. This will expel any water from the waterlock and the exhaust pipe without sucking in any more water.
What do you think is wrong with the waterlock as not sure what damage you can do by turning it over with the starter.
 
Tranona said:
The waterlock is downstream of the engine so you can shut off the water intake and turn the engine over with the starter. This will expel any water from the waterlock and the exhaust pipe without sucking in any more water.
What do you think is wrong with the waterlock as not sure what damage you can do by turning it over with the starter.
Click to expand...
Before winter I opened water inlet strainer and pour antifreeze in it without started engine. Since the boat is on hard I'm a bit afraid it could go into the cylinder as I didn't realized it is dumb idea.
 
Was the engine running and the intake valve closed when you did that? There is no reason why the water should get into the engine as all you have done is fill the seawater circuit with AF. No different from leaving it full of seawater.

Suggest you keep the intake valve closed, remove the lid of the strainer so that you can add extra water from a bucket and turn the engine over. This will expel the AF and replace with fresh water. Best to do this on the hard so that you can collect the AF and dispose of it rather than pumping it into the sea.
 
Tranona said:
The waterlock is downstream of the engine so you can shut off the water intake and turn the engine over with the starter. This will expel any water from the waterlock and the exhaust pipe without sucking in any more water.
What do you think is wrong with the waterlock as not sure what damage you can do by turning it over with the starter.
Click to expand...

You misunderstand, so (with respect) this is bad advice.

The OP thinks water has got into the engine and "waterlocked" it (hydraulic lock). Cranking the engine could cause damage in this case (if he was correct). I doubt very much that he is correct though.
 
miracze said:
Before winter I opened water inlet strainer and pour antifreeze in it without started engine. Since the boat is on hard I'm a bit afraid it could go into the cylinder as I didn't realized it is dumb idea.
Click to expand...

There is no path from the inlet strainer to the cylinders.

Just pull the engine stop out and crank the engine to pump the antifreeze into a bucket, to dispose of correctly. You could, as Tranona suggests, tip some fresh water in through the strainer top.

There really isn't any point in running antifreeze through this engine to "winterise".
 
Tranona said:
Was the engine running and the intake valve closed when you did that? There is no reason why the water should get into the engine as all you have done is fill the seawater circuit with AF. No different from leaving it full of seawater.

Suggest you keep the intake valve closed, remove the lid of the strainer so that you can add extra water from a bucket and turn the engine over. This will expel the AF and replace with fresh water. Best to do this on the hard so that you can collect the AF and dispose of it rather than pumping it into the sea.
Click to expand...
I did it with engine off and closed raw water inlet. That's why I'm afraid it could get through exhaust pipe back into the cylinders.

PaulRainbow said:
There is no path from the inlet strainer to the cylinders.

Just pull the engine stop out and crank the engine to pump the antifreeze into a bucket, to dispose of correctly. You could, as Tranona suggests, tip some fresh water in through the strainer top.

There really isn't any point in running antifreeze through this engine to "winterise".
Click to expand...
Since the boat was on hard I was afraid the exhaust could be higher then the cylinders so it could get back through the exhaust pipe.
 
miracze said:
I did it with engine off and closed raw water inlet. That's why I'm afraid it could get through exhaust pipe back into the cylinders.


Since the boat was on hard I was afraid the exhaust could be higher then the cylinders so it could get back through the exhaust pipe.
Click to expand...

How much antifreeze did you pour in ?
 
PaulRainbow said:
How much antifreeze did you pour in ?
Click to expand...
about 6-8l I was pouring until it didn't stop draining from the inlet strainer :(. Now inlet water strainer is full, the antifreeze is not comming anywhere else. I disassembled exhaust hose and it's completely dry.
 
PaulRainbow said:
You misunderstand, so (with respect) this is bad advice.

The OP thinks water has got into the engine and "waterlocked" it (hydraulic lock). Cranking the engine could cause damage in this case (if he was correct). I doubt very much that he is correct though.
Click to expand...
I understand that but I fail to see how just pouring antifreeze into the strainer can get into the engine. If it was running then the waterlock would collect it in the normal way. If it was not running then it won't get past the pump. The fact that it is AF is irrelevant. Also fail to see how the exhaust can be higher than the cylinders just because the boat is on the hard unless it was dramatically nose down.

If he really is worried then just disconnect the exhaust from the engine.
 
miracze said:
about 6-8l I was pouring until it didn't stop draining from the inlet strainer :(. Now inlet water strainer is full, the antifreeze is not comming anywhere else. I disassembled exhaust hose and it's completely dry.
Click to expand...
Open the seacock and drain the filter. Remove the pump impeller and catch any AF that drains out. You say you have removed the exhaust - was that from the engine? and it was dry, then fail to see how it can have got into the engine as that would only happen if the engine was running and sucked it in.

If you do feel the need to put AF into the seawater system and it is not really necessary unless you are in a very cold and exposed location, do it with the engine running and stop when it has expelled all the seawater out of the exhaust.
 
Tranona said:
The waterlock is downstream of the engine so you can shut off the water intake and turn the engine over with the starter. This will expel any water from the waterlock and the exhaust pipe without sucking in any more water.
What do you think is wrong with the waterlock as not sure what damage you can do by turning it over with the starter.
Click to expand...
OP believes that the engine may have hydraulic lock up and is not affected by exhaust water lock
 
scottie said:
OP believes that the engine may have hydraulic lock up and is not affected by exhaust water lock
Click to expand...
Yes, I understand that - just don't see how it can have happened because of what he did. The only way fluid can get from the inlet strainer is if it somehow fill the whole seawater system, gets injected into the exhaust, fill the waterlock to the point that it goes back up the exhaust elbow into the manifold. He says he has removed the exhaust and it is dry. Water getting back into the engine occurs when the engine is running and water gets sucked back in or through syphoning, neither of which seem to be happening here.
 
miracze said:
about 6-8l I was pouring until it didn't stop draining from the inlet strainer :(. Now inlet water strainer is full, the antifreeze is not comming anywhere else. I disassembled exhaust hose and it's completely dry.
Click to expand...
If that is the rubber hose at the exhaust manifold/swan neck on the engine then you have not filled up the cylinders with water; reassemble it all, stop worrying and go boating.
 
You must log in or register to reply here.

Share this page

Top