Engine woes... replacing the raw water pump but can not get to it. Engines and Such Forums

Not a very specific title but it's been that sort of day.  Our DE 38 was repowered with a Yanmar 56hp 4JH3E.  It's been a good engine...but the raw water pump leaks.  We went to try and get at it today...FAIL!  The engine essentially sits on the lower bolt of the water pump, and the brackets that were made to hold the engine block were notched out to access to that bolt but it's too small to get a wrench back in there.  And of course the bolts that are there are rusted from the water leak and not budging.  Figuring out what to do...as while the water pump still works...it leaks and that is obviously something we will need to be able to access in the future.  

Anyone on here repowered with this or a similar engine?  Or any thoughts?  Was hoping to not have to haul the entire engine up to get to this...