possible bad rectifier?!? help

section8

Petty Officer 2nd Class
Joined
Jul 27, 2007
Messages
120
hi all. me again. i wanted a second opinion before placing an order. i think my rectifier is bad. sometimes but not always i look at the voltage guage and it goes up to 17 volts or so. usually when im at half to full throttle. if i touch the power trim button up or down it drops to 12-13 or so but after pushing trim button it rises again it wasnt blown any electronics or the batteries yet. i assume its the rectifier. should i pick up another? they are $25 here at i boats and im placing a order anyway for other stuff. whattya think???? THANK YOU ALL. where would any of us be without this forum? probrably on the lake hoping for someone to come by and tow us in.....!
 

ajgraz

Lieutenant Commander
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Mar 1, 2010
Messages
1,858
Re: possible bad rectifier?!? help

Assuming you have an unregulated charge circuit (like most old OB's), sounds like it's working correctly to me.

Plain old rectifier will apply in excess of 16-17 VDC. When you apply power to T&T (or anything else, for that matter) while charging, it creates a load that regulates the voltage downward toward battery voltage.

What OB have you got?
 

section8

Petty Officer 2nd Class
Joined
Jul 27, 2007
Messages
120
Re: possible bad rectifier?!? help

its a 1989 v135 black max. it charges fine and starts well but that voltage seemed high. what would a bad rectifier do to alert me its going? thank you much
 

sschefer

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Nov 13, 2008
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4,530
Re: possible bad rectifier?!? help

its a 1989 v135 black max. it charges fine and starts well but that voltage seemed high. what would a bad rectifier do to alert me its going? thank you much

Rectifiers simply rectify A/C voltage and give you DC voltage as a result. They do not control the voltage (regulate). Instead, they rely on your battery to do that and if it's in good shape it will do just fine.

You can upgrade your system with a recitifer/regulator from a newer engine and solve the over voltage problem. These are readily available for around 100.00 and some change. There are still some of the older style two wire regulators around that were put on the 90 and 91's but they're pretty hard to find. If you have a 40 amp system you may or may not need two rectifiers/regulators depending on your stator.
 

j_martin

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Sep 22, 2006
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7,474
Re: possible bad rectifier?!? help

its a 1989 v135 black max. it charges fine and starts well but that voltage seemed high. what would a bad rectifier do to alert me its going? thank you much

Low voltage = bad rectifier.
High voltage = bad battery or battery connections.

You need to keep the water up in your battery. It will use some in this system. If it has ever gone below the plates, the battery is toast. Replace it and maintain it.

hope it helps
John
 

sschefer

Rear Admiral
Joined
Nov 13, 2008
Messages
4,530
Re: possible bad rectifier?!? help

Low voltage = bad rectifier.
High voltage = bad battery or battery connections.

You need to keep the water up in your battery. It will use some in this system. If it has ever gone below the plates, the battery is toast. Replace it and maintain it.

hope it helps
John

99.99999999999999999999999999999999999% of the time:rolleyes:
 

section8

Petty Officer 2nd Class
Joined
Jul 27, 2007
Messages
120
Re: possible bad rectifier?!? help

i have a two battery system with a perko switch. one battery is new last year. one of those wal mart dual purpose marine trolling/starting and the other is new this year wal mart marine starting. thanks for the help. i know both work fine and once i get the other issues taken care of ill try switching to one and the other and see if only one is upping the voltage.probably next weekend. for now im not gonna order a rectifier so thanks a million!
 

ajgraz

Lieutenant Commander
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Mar 1, 2010
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1,858
Re: possible bad rectifier?!? help

Before you blow any bux on a new rectifier, do you have an ohmmeter with a diode function? You can do a simple continuity check on the diodes in the rectifier. If they are good, the rectifier is good.
 

sschefer

Rear Admiral
Joined
Nov 13, 2008
Messages
4,530
Re: possible bad rectifier?!? help

Before you blow any bux on a new rectifier, do you have an ohmmeter with a diode function? You can do a simple continuity check on the diodes in the rectifier. If they are good, the rectifier is good.

That's absolutely correct. The problem you are having is regulation. Rectifiers do not regulate voltage and Diodes, in this type of application, very rarely short. They usually burn through and go open which would show up as a lack of charging voltage.

Try bypassing the Perko Switch first and see if that has any effect.
 

section8

Petty Officer 2nd Class
Joined
Jul 27, 2007
Messages
120
Re: possible bad rectifier?!? help

i'll try taking the perko out and try each batt. separately. if they didnt even use a regulator on my motor why would i need one and how would the motor not need one. its a 1989 and works ok so its been working this way for 20 yrs. should i just not worry about it? what is in it to make it regulate voltage or does it just create that voltage regardless. its getting a little confusing?im not sure why taking the perko switch out would regulate voltage but i am gonna try it to rule it out!
 
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