I had the same problem with my raw water pump on my 2gm 13 when I bought my 1981 30' Hunter last year. I called my local Yanmar distributor and they told me they had a complete replacement pump with bracket much cheaper than the rebuild parts. I bought this replacment and found it fit but the intake and output fittings were in slitghly different places and the output was a bit different sized. I had to buy a new output hose but everything else worked.
I'm not at the boat so I don't have the part number but you can call these people and get it. Yanmar Distributor Marine Pro of Central Florida - Complete Re-power Service