1980 Phantom with 470 Mercruiser engine

I recently purchased this old boat. I have some questions for anyone familiar with this engine. First, the old mechanical and newly purchased mechanical don't seem to be pushing fuel despite some barely visible marks on the tang. An Autozone 2 to 3.5 lbs. electric gets hotwired to the battery for it to run which it does. However, when under a load in the water it doesn't go faster, just hesitates then backfires slightly out of the carburetor. I have a rebuild kit for the carb coming, but, in trying to wire up a toggle switch for the pump the wires get hot and have to be immediately disconnected. Obviously I have to properly wire this switch (I've read briefly about oil pressure switch, relay etc.) I'm wondering if that low pressure pump is inadequate to begin with, need 7 lbs? Any help with this boat moving forward would be greatly appreciated!

Low pressure pump is fine. Check you compression timing and rebuild the carb. Wonder if the fuel pump love is worn off the cam.

unfortunately for you the 470 and other engines in the 3.7 l four cylinder were short lived and fairly problematic. Very prone to overheating and blowing head gaskets. There’s guys with experience to help but I suspect most of the advice you get will be to run...

Dieter, thanks so much for your reply! I haven't even checked my email since my post. I'm a 470 Mercruiser owner now , so, all my time is spent working on it, researching it, ordering parts for it, (or at least trying to order parts for it) etc. You were right about the lower pressure pump working, had a local carburetor expert go through and rebuild it for the 2nd time in 3 days, he did an excellent job and fine tuned the linkages and throttle that were a bit off. My obssessive dream of the craft being ready on the 4th was dashed however when the starter motor failed to turn the engine over even once. I plan on one day writing a book about this horror story and I'll need my updates for notes. Thanks for listening, I'm going to see if I can find any info on my WW2 starter motor.