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Question on clearance when boring and honing a 50hp two stroke block.

L

Lock45

New member
Do you need a special boring bar and hone for a Mercury 50hp two stroke block? Is there a danger of crashing the boring bar into the lower saddle area of the block? Can you pass a hone straight through the whole length of the cylinders or will you run into an interference problem with the lower end of the cylinder? I have had a few other makes of outboard engine blocks machined with no problems but have never had a Mercury bored and honed. My local automotive machine shop has done some outboards for me in the past, with good success, but they were not Mercurys. Those blocks allowed for straight through boring with no interference problems. Is there any member here with machining experience on Mercury 50hp two strokes the may be willing to answer these questions or even take on the job? Thanks in advance for any information.
 
Take a good look at this motor.----I think you will see that there is no cylinder head.----Shop would have to bore and hone a " blind hole "
 
I will be cracking it open next week. If the cylinders are blind, with no removeable cylinder head, then I need to find an outboard marine machine shop. That could be a challenge here in Southern Ontario.
 
Lock45 said:
I will be cracking it open next week. If the cylinders are blind, with no removeable cylinder head, then I need to find an outboard marine machine shop. That could be a challenge here in Southern Ontario.
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Also consider a motorcycle rebuild shop, many motorcycle "jugs" are blind bore design, so your 50hp Merc would not be challenge to do the machine work. You will need to measure each bore to select which size oversize piston you might need. Most shops I've encountered want the pistons in hand and bore the engine to the piston size to get the skirt clearances correct. Many engines with low hours ,may have straight, round bores within spec and just need a deglaze and fresh rings.
 
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