Hi
I wonder if someone can help. I am in the UK and I've bought a 1984 22ft Fletcher (UK boat) that has been re-engined at some stage with a Mercruiser engine with what appears to be a TRS leg. The serial number (which is on the back of the engine near the transom) is A399345. I've looked on a few sites and this code is not recognised. However, if you put a 0 (zero) in front it is shown as a 7.4 litre TRS 454 rated at 420hp from circa 1987. HOWEVER, the guy I bought it from guarantees it is a 5.7 litre. Please can anyone help me? I need to take the boat to a specialist Mercruiser mechanic but that is 310 miles away. I'll attach some photos for reference. Thank you in advance for any help / confirmation.. Rob

You really don't need a serial # to tell if its a SB or BB

One picture of the engine we could instantly tell you if it was a big block or small block, but not much more. Perhaps a picture of the serial tag as well.

Hi I've tried to post photos but I don't think I can until I've made 10 posts. In the meantime I reached out to Mercruiser customer support and received the following information via email:-

" This is a race engine. Serial was 0A399345 and was sold to Cigarette Racing 1/09/1987.

Description: PPM 420
Year: 1987
Cubic Disp: 454.00

No good information on this engine. The drive could be a TRS."

Out of interest can anyone post pictures that illustrate the difference between small block and big block: I'm afraid here in the UK we don't have many examples to compare.

Kind regards

Rob

Pm'd