Alternator upgrade on Yamaha ME420

[YahamaME420 owner]

Hi,

I got twin Yamaha ME420 direct drive on my boat.
Alternators are only 55 amp and I want to upgrade to 120-130 amp. Could go higher but my Sterling dual engine relay are limited to same anyway.
I am sure similar question has been posted many time over but my question are related to the Yamaha engines.
Might be a dumb question to bare with me.

1. Any reason I cannot use a Yamaha 1HD (Landcruiser) compatible alternator for which even 130 amp seems low/mid range. ME 420 only goes to 80 amp. Any reason the marine version should be limited to 80?
2. By upgrading the alternator output any reason I cannot run a separate positive (and negative if needed) directly to the battery i.e. disconnecting b+ from alternator to back of starter solenoid?
Kind of hard to see what else the B+ from alternator is doing (if any) through the wire harness without messing with Yamaha engine management.
3. Can I put an external alternator regular on a 1HD/ME420 engine? In this case Sterling power alternator regulators but I cannot imagine the brand here is important. Need or not?

As I understand the alternator to battery will now have to be fused so 1.5m 35mm cable with 150 amp fuse I would imagine.

From what I can tell this should be fine but I dont want to find out the hard way if not.
You kind support is much appreciated.

regards

 

[nfluester]

Dont see why not. belts are normally the limiting factor of how many amps you can pull, from memory the ME420's have dual V belts so you should be ok with upto ~150 amps.

I have not played with alternators on the Yamaha but have upgraded on both Volvo KAD and D6, you may find you will need the lamp output to drive the Rev counter if it's not coming from somewhere else, you also will need the D+ for the charging alarm buzzer / light

for external regulation you will need to get the alternator modified to have the field output from the brushes and then feed a sperate D+ to the alarm circuit depending on what regulator you go with, on balmar they suggest using a relay on the Wakespeed they have a seperate output you can feed in