1988 Mercruiser 37 Voltage Gauge Fluctuation

"Voltage Gauge Fluctuation on

"Voltage Gauge Fluctuation on my 1988 Mercruiser 3.7. I have read many discussions regarding the Voltage Regulation System on the 3.7 Mercruisers as being "God Awful". The boat I purchased from a friend has been very well maintained and has only 153 hours on the 20 yr/old engine. The engine seems to runs well with the exception of the voltage gauge. It normally runs @ approx. 12.5/ 13 volts. Then all of a sudden the gauge will peg out @ 16 volts. While the voltage is @ 16 and I use the trim or any other accessory requiring voltage, the gauge goes crazy (jumps around) and the engine starts to sputter. Has anyone had this problem and could this be the V/R going bad. Note: I have two new batteries on-board and have had them tested OK. Thanks, Rick."

"Engine sputters when the V pe

"Engine sputters when the V pegs - yes, I would suspect the regulator. If it is one of those water-cooled jobs they are about $400 last I checked. Mine went bad - high v making plugs misfire, just like yours is doing. I installed a belt-driven alternator for about $110 and no more problem. Let me know if I can help. JW in Dixie"

"Warren,
Thanks for the infor

"Warren,
Thanks for the information. Did you purchase the alternator mount or was it something you fabricated? I have read other post that indicate people have bought OEM alternators and made their own brackets. I am pretty handy, but I don't really have the ability to manufacture a bracket."

"I made the bracket from 1/4&#

"I made the bracket from 1/4" X 1" flat bar. Used a threaded rod for the alt. Then another piece of flat for a tension holder. Alternator bracket

try an auto junkyard for a bra

try an auto junkyard for a bracket

"Gentlemen, I appreciate the f

"Gentlemen, I appreciate the feedback. Nice work on the bracket. One more question. What size/ amperage alternator did you purchase? I am assuming an 85 amp - 105 amp would be sufficient."

That was eight years ago and I

That was eight years ago and I don't recall. It could have been as little as 40A - that is plenty for my boat. JW in Dixie

"Hey Rick, no one has mentione

"Hey Rick, no one has mentioned it but make sure you get a "marine" alternator as sparks aren't good in the engine compartment"

You want a 60-65 amp single wi

You want a 60-65 amp single wire marine alternator. Use a minimum 10 ga. alt. output wire; for 65-90 amp. preferably an 8 ga. wire. For 100 amp. use a 6 ga. wire.

"I would like to thank all of

"I would like to thank all of you that have sent in your input. I grealty appreciate it. Do to the fact my boat has Power Steering and not a great deal of room in the Dog House, I have decided to bite the bullet and purchased a Conversion Kit. The (NEW) kit comes with a nice professional Wagner Alternator Bracket w/ Tension Arm, the Balanced Drive Pully, New 68 Amp Marine Alternator, Drive Belt and all the other misc. parts required to make the conversion. I paid $ 392.00 including S&H. I'll let you know how I make out. Thanks Again, Rick R. }"