I have twin mercruiser 260's I believe both of my alternators and or voltage regulator are shot I took the port side alternator off today to have it checked and it was only putting out 8 amp I believe can the regulator cause this? Or do I need to replace the whole unit? The regulator is on the back side I believe part number on alternator is

Mercury Marine # 98555
Output 12v 55amp
Vendor# Ar-150
Date code 01-86sae Marine J1171

Go on Amazon.com and buy a marine alternator its cheaper that just replacing a voltage regulator.

http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

They said 1987 and up it can't be much different can it?

Try this Your Model number is listed in this replacement

http://www.amazon.com/New-Mercruiser...555+alternator