I had the same issue last year when I went thru this upgrade, and I just took a picture of the plug and receptcale on the MG with my cell phone, then went to the local marine dealer. They are a standard plug, my tracker pt175 had the type with a "v" notch in the plug, dealer had one for $8, spliced/attached it directly to the motor leads and used some shrink wrap to seal it it. The plug will come with short 6" leads as well, just get some good butt connectors and shrinkwrap. BPS has/had the same plug for $17, for once the dealer was a better deal.

Also get one of the "resettable" circuit breakers, find the in line fuse, and remove it, then make the ring connections for the resettable breaker. Will make it much easier if the fuse blows, just push the reset button and keep fishing. Holler if you have issues. EZPZ.

GL mounting your MK.