1995 4.3LX Webber 4BRL Dies on Throttle-up

I need some help, first, brief history
2003 same issue, replaced electric fuel pump ,ran fine until now.
I put another pump in this year,supplier said their was a bad run on these
merc pumps in 02-03. So, first time out
Last week,running fine 20 min then she began to bog down. Runs fine at idle
If I disengage prop RPMs are no problem. Opened hatch and there was
slight stream of smoke coming from alternator, I quickly shut her down.
Turn the ignition switch to on and gages pegged.I removed the ALT
Had it test and repaired, It was overcharging @16volts ( I do not think
that this is related to my running issue?

I noticed when I installed the second pump I heard it energize with
ignition in the (ON) position not start, I am aware that the oil pressure switch
sends power to this pump when cranking.

My mission is, this weekend. Install ALT Check for voltage( non cranking
at the fuel pump, check for bad connections all around.Check coil volts.
One more thing. My neg battery wing nut(sst) was Brown from what I think
was the ALT over charging the battery AGM.Could this have damaged
any thing like my new fuel pump? Guess I need to check output.

My question is Do I have 2 unrelated problems here.I still think
I have a lean mixture issue. Should I have a anti siphon valve
near the fuel tank? There is no other fuel filter in the system
other than the w/seperator,I changed this out yearly.

Reading the Posts on this site,I see their is a lot of Knowledge
out there. Any ideas, I would greatly appreciate.

Best Regards
JC

One more thing,This power Plant is inside a Donzi Classic 16
To work on this thing is like doing surgery on a soft ball
inside a 16 oz coffee can.

Re: 1995 4.3LX Webber 4BRL Dies on Throttle-up

JC:
I am not one of the pros here, but I know a lot about my own boat. It sounds to me like you have an electrical problem. Your ALT very well may have fried your pump and your battery - depends how long it was overcharging. I would suggest that among the things you are planning you add removing all wing nut type connections and get proper terminals, preferably bolts. It's possible that you may have lost that ground while underway and caused the other problems. I don't know what type of AGM's you have but my Lifelines only have bolt terminals. Wing nut terminals are for lawnmowers.

You do have an anti-siphon valve (or should anyway). It is probably what the other end of your fuel line is connected to on the tank. All it is is a (usually) male NPT to hose barb aluminum fitting. Inside there is a spring and a stainless ball. If you are going to check it, buy a new one and replace it. It's not worth getting to (esp. given the coffee can scenario) only to leave the old one in there. However, if you're getting good flow from your pump it's probably fine.