New or Re conditioned Bukh dv20

[Tranona]

Indeed. There are some boats that can use the old British automotive derived 4 cylinder diesels in the 30-50hp range such as BMC 1.8, Perkins 4/99 and 4/108, Ford XLD where there is still a plentiful supply of both engines and cheap spares plus cheap marinising bits. However most small boats that use engines in the sub 30hp do not have room for such engines (nor need them) and therefore are limited to the industrial engine based 2 and 3 cylinder engines. Most of these are difficult and expensive to rebuild primarily because the parts, particularly the marinising bits are so expensive. Heat exchangers at £2k a pop for example. If the engine is linked to a saildrive the options are even more limited.

Fortunately in some ways that the newer type engines are more refined and if properly maintained will last 30-40 years. However if you are buying a smaller boat from 30-40 years ago you are likely to find many are for sale because the engine is in the danger zone just as the OP has found.

 

[LittleSister]

There are some boats that can use the old British automotive derived 4 cylinder diesels in the 30-50hp range such as BMC 1.8, Perkins 4/99 and 4/108, Ford XLD where there is still a plentiful supply of both engines and cheap spares plus cheap marinising bits.

A friend's boat was powered by a Perkins 4/108 that had come out of a crashed Post Office van! That proved effective for many years until he sold the boat. I think he had serious trouble only once, when the core plugs came to (becasue it was raw-water cooled, perhaps? I can't remember now).

. . . the industrial engine based 2 and 3 cylinder engines. Most of these are difficult and expensive to rebuild primarily because the parts, particularly the marinising bits are so expensive. Heat exchangers at £2k a pop for example. . . .

Might be a much cheaper option to replace it with a remote generic heat exchanger such as a Bowman?

 

[Tranona]

Might be a much cheaper option to replace it with a remote generic heat exchanger such as a Bowman?

In theory yes, but in practice no because in most cases the HE is also the exhaust manifold. Add to that if you then start taking the engine apart you find that many cannot be bored for oversize pistons and the oily bits and gaskets are also high priced. Even the Perkins based Volvos and Kubota (Beta) which are used in many industrial applications are high priced.

Actually very few of the newer type industrial based types have got into that window yet. It is the old (pre 1990s) Volvo, Bukh and early Yanmar that are the most common types in the sub 30hp that need replacement