Volvo Penta AD31 series question

[pantjo]

What are the difference between the following engines:

AD31A
AD31B
AD31C
AD31P
AD31L-A

I am not looking for a detailed parts explanation of course.
I am just wondering if there are any substantial differences and why on earth Volvo has so many different variations on the same theme?
I own a AD31L-A (is there a AD31L i wonder) and a friend a AD31B and we have the same question.

 

[Bondo]

Re: Volvo Penta AD31 series question

Ayuh,... I believe it designates Vintage...

 

[Don S]

Re: Volvo Penta AD31 series question

They changed the letters when they made major changes in the complete engine, it may be the cooling system (lots of changes there over the years) internal changes to newer styles and designs. electrical changes, the induction manifolds have changed, filters changed, injection pumps & timing. The letter changes like P-A, P-B etc.were minor model changes done during a production run, Simple things like changing a circut breaker location would be a minor change.
Year really had nothing to do with it, as an example the A model could have been used for say 5 years, and the C for only 1 year, or even less if there was problems.