I took the heat exchanger off the right hand engine on Silver Dragon today, because the pressure cap and fitting are missing. I will get the local radiator repairers to fit a new one. It has a plate on it that shows it was made in summer 1978, which agrees with the age of the boat. It was made by Bowman, and was fitted to a BMC 2.5 diesel.

The heat exchanger tubes are clean as a whistle, but the exhaust manifold ports were hugely (about 50%) blocked with carbon deposits. It seems that 30 years of slow cool running takes its toll! It reminded me of decoking a two-stroke!

It was dry soft carbon though, not at all oily.

This made me think it would be good to do the other one, but access to that area on the left hand engine is not good on the Birchwood 33.

Hi there, it is generally accepted that running a diesel engine under a very light load, as per boating, can produce copious amounts of carbon and encourage glazing of the cylinder bores. One boater that I heard of would tow behind him in the river a large lorry tyre and to maintain speed needed to open the throttle and make the engine work. Wish you well.

The radiator people fitted a new fitting for the pressure cap and supplied a pressure cap. £55 incl VAT.

Oddly, when we pulled the heat exchanger off the left hand engine there are no carbon deposits!

We cleaned and flushed the heat exchanger tubes, and refitted the heat exchanger with a new gasket.

Access is actually pretty good, my son got between the engine & fuel tank with no problems!

All back together now.