salt water in single cylinder

[Scott06]

So I have a line on a cheap 2003 supposed mercruiser 090 block running engine, no manifold. Does the 090M stand for marine. How can I tell if it is marine and not just GM?

090M is for metric. For some reason they used metric fasteners on some of the 4.3 blocks... in true GM fashion only some of the threads are metric- starter bolts, flywheel cover, and front/side motor mounts. I bought about $40 worth of SAE bolts to convert when I did my repower.

If you are buying a complete used engine doesn't make any difference, only when you are mixing and matching parts is it an issue

Never found an answer as to why they mixed metric and SAE threads on the same block. I can understand one or the other but both on the same block makes no ducking sense

 

[Lou C]

There are no “marine” blocks or heads only add ons like the head gaskets, core plugs etc. the M refers to the us of some metric fittings. In that case if you use it be careful with threading in fasteners in fact you might want to buy an SAE/Metric thread chaser set so you can check them first!

 

[Lou C]

If you wind up going with it & still have those one piece exhaust manifolds it’s a good time to ditch them for the 2 piece conversion. Barr marine makes a nice one check out Lighthouse Marine in Riverhead…,