Originally Posted by
NERSTROM
I think the Mirage was one of the best engines I did at OMC. The 25 and 35 share the same block and lower unit castings making all port passages and exhaust tuning the same between the two versions. Increasing the bore size of a 25 and readjusting port timing makes it a 35 block. I may have posted some history on the origin of the design in an earlier post. The block is of lost foam construction and due to the small bore size there was a tendency for glue lines to partially block the posts. Unfortunately, this is the case with many of the blocks. Someone willing to take the time to grind out the glue lines, especially in the finger ports is going to be pleasantly surprised at the increased performance. The air box that came with the engine was a patented design and while reducing noise also increased power. I have never found air horns to be of much benefit, although they do look nice. Darn cold here in Chicago!
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