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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10901
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a 1970 Fiberform boat with a 4 cylinder Mercruiser

Customer Question

I have a 1970 Fiberform boat with a 4 cylinder Mercruiser engine and stern drive unit. The serial number on the block is(###) ###-#### According to a book I bought on Mercruisers it should be either model 60, 80, or 90. Also according to the book all of these models are aluminum with steel sleeved cylinders. My block is cast iron (a magnet sticks to it). So I'm trying to figure out what I've got. Can you help me out?
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello Charles. My name is Tan.

Your engine is a 153 cubic inch Gm engine. This is a cast iron engine. They call this motor the Iron Duke.

Here is a link.

Post back with questions.