Thornycroft 108 water pump pulley

[allenby]

Hi

I have a Thornycroft 108 (BMC1800) in my Jonathon Wilson boat (1989) and the cooling has always been poor, because the keel tank is built into the baseplate - it's  a very

early JW

I am looking for a smaller diameter water pump pulley to improve water circulation at low revs - my original pulley is 6 inches across the flanges, and looks

as though it was a bespoke welded up Thornycroft part - there is no part number

 

Does anyone know what smaller diameter pulleys might fit - and where I could get one?

Hopefully

Alan

 

 

[Tony Brooks]

I am assuming this is the engine water pump and not a rubber impeller "raw" water pump.

 

I can't see Thorneycroft welding up a special pulley. It's a BMC part and, I think, common across all the BMC B series engines, like an MGB. 6" across the flange makes little sense, the water pump flange is more like 3" I think with the outer diameter more like 4". The standard one is pressed and spot welded steel. I think Calcutt can supply a standard one.

 

Thorneycroft may have fabricated one if it's a wide polyV belt or a special fitment.

[Tracy D'arth]

The standard pulley off the Sherpa van which is the origin of your engine is smaller than 6".  The same pulley is used on the 1500 engine, in fact on practically all BMC engines, petrol and diesel.

ASAP should be able to provide.

 

Base plate tanks are subject to air locks which severely reduce the cooling, have you been able to ensure there  is not an airlock?

[allenby]

Yes it's the engine water pump. I have the pulley in my hand, and it's 6 inches across the flanges.

This one is not pressed and spottwelded - it's very solidly built - mounting boss thickness measures 3mm

I assumed it would be the same as an MGB one - but a friend of mine with 2 MG Jubilees might not take kindly to me taking one apart to check!

I will find one somewhere

Alan

 

[allenby]

No airlocks - have had the boat for 32 years so am used to it...and the possibility of airlocks

Cooling has _always_  been poor at low revs ;-(

Much better when hammering up the Thames!

 

Alan

[Mikexx]

9 hours ago, allenby said:

Cooling has _always_  been poor at low revs ;-(

 

 

What's the return temperature like?

 

If low, perhaps this is more of a blockage or constriction in flow?

 

What temp thermostat do you use? What is the temperature of water leaving the thermostat housing.

 

I would wager any B-series pulley would fit unless there have been other mods to the crank - pulley system.