mercruiser sea (raw) water pump

I just installed a new impeller in to my sea water pump for a Mercruiser 5.7 with a Bravo II stern drive. The pump housing has one bolt that threads into the front part of the housing, the remaining bolts that hold the housing together have nuts. The bracket that mounts to the block is directly under the nuts, and covers the threaded hole for that one bolt.
Is there any reason in particular that this bolt does not have a nut? The front housing threaded hole is stripped. I tried running a tap through it, but the soft aluminum threads are weakened, and without going to a larger size bolt which I don't know is possible, the best option would be to drill the engine mounting bracket and put a nut on this bolt like the other ones. Is there any problem you can foresee if I do this? There must have been a reason this one bolt did not have a nut because it looks like it is a straight forward job to drill and put a nut on it.
Thanks for any help you can provide.

Re: mercruiser sea (raw) water pump

How about an engine serial number, those pumps change from year to year, just like other engine parts.

Re: mercruiser sea (raw) water pump

If there would be no interference with anything I would say easy fix to nut it.
Don't over-tighten.

Re: mercruiser sea (raw) water pump

The engine is about a 1987. The engine serial number tag fell off when I had the block in to the engine shop for a hot wash to clean it up. I should have written the number down before hand but didn't. I can include a pic of the pump with bracket installed. You can see the nuts for each housing bolt, and then the one pump housing bolt channel with no hole for the bracket. That is the one that is threaded.

Re: mercruiser sea (raw) water pump

tailwind, turn the pump and see if the hole lines up better. I swear that I used to be in the same situation as you, but then I'd rotate the pump or the bracket and it would be fine.

Re: mercruiser sea (raw) water pump

I'm not sure you can see any better in the picture that I have . . . but here it is . . .



comparing the 2 pictures . . . I think you may have the bracket on wrong . . .

Re: mercruiser sea (raw) water pump

I don't think it is possible to put the bracket on wrong. The layout of the bolt holes has the spacing of two holes close together and the rest further apart. It only lines up one way. The two bolts I am refering to are the bolt channels at the top of your pic. For some reason though I see a hole in your bracket but no nut on the two that are close together.