Hello

I have recently bought a Mercury outboard motor and I'm a new member here in this Mercury forum. I have been a member in the Yamaha forum for many years and have received a lot of help there and thank for that. Good to be here also.

I decided to open a thread because my friend's 2-stroke 55 (1994) blew a piston. He then got a brand new powerhead but that is year 1997. The seller did not tell him that it is different. Can this 97 model powerhead be used with the 1994 mid-section? How about the hole in the block? Shouldn't that be blocked?

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I have here pictures of different mid-sections and the old one on the left is the one that needs to be used because only that fits into the outer housing.

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I was going to test if cooling water flows right using the old mid section but can someone tell whether I'm worrying for no reason.

Thanks JJ/Europe

Can you obtain the serial numbers from both motors? There is a freeze plug on the blocks with the serial number. With this information I can obtain more accurate information.

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Hi, the old blown powerhead was 0D054302. The new one is 0G642533.

What motor is that new one, is it 55 or 60hp?

Thank you, JJ

Well the original powerhead is actually a 1991 50HP, the new powerhead is actually a 1998 Mariner 55HP. The blocks are not interchangable. There is no discription as to what the differences are.

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Mercury Outboard Parts
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The difference is the 1991 block is a small bore 51 ci and the 1998 is a 58 ci..