Difference between merc 800 and 850

What is the differences in the merc 800 and 850..I have looked at the part index and can not find the diff?

Re: Difference between merc 800 and 850

The difference between the 800 and the 850.The 850 had something altered in the exhaust setup.I am guessing you are reffering to the early 70's inline 4 Merc.On a side note if you are thinking of making your 800 into a 850,I was told I would never know the difference.

Re: Difference between merc 800 and 850

If you're referring to the diff between the '69-'71 800-4 and later model 850-4's, the 850 has power-ported pistons and different block to match the pistons. Plus the bottom of the block is cast differently to match up with the revised exhaust tuner used on '72-and-up 66c.i. Fours and 99c.i. Sixes.

You could use the later 850's rotating assy (crankshaft, bearings, pistons, rods) in an 800 block but you couldn't use the 800's pistons in a later power-ported block. The power-ported pistons' holes would have no effect when used in an 800 block, since that block wouldn't have the corresponding passages cast into the block.

Hope that answers your question, if not you'll have to be more specific about which models/years you're asking.

HTH............ed