Radio Shack Rectifier and heat?

sramelyk · Jul 6, 2005

I concluded my rectifier was bad.. I had the same voltage not running and running at about 2500 rpm.. I purchased the radio shack full-wave bridge rectifier rated for 25amps.. I installed it and now when idled up to 2500 rpms I go from 12.6v to 13.4 volts.. Which seems to atleast be charging a little, and I would also assume at higher RPM's I will get a higher output. My question.. The rectifier is getting really hot. Is this normal? It looks like the old rectifier was mounted to the block providing a great heat sink. Should I worry?

timmathis · Jul 6, 2005

Re: Radio Shack Rectifier and heat?

Does the new one have three post?

timmathis · Jul 6, 2005

Re: Radio Shack Rectifier and heat?

If so. I think you ground one. There was A post about this not long ago, I'll try to find it and get back with you. Tim P.S. you try to find it also. Good luck

Silvertip · Jul 6, 2005

Re: Radio Shack Rectifier and heat?

A rectifier of that capacity needs a heat sink.

sramelyk · Jul 6, 2005

Re: Radio Shack Rectifier and heat?

It was a four prong.. 1 ground, one positive to the battery and 2 AC's.. Which are going to the stator. What kinda of heat sink? Do I just stick it on the back of the rectifier? Would I be good for a weekend of boating? I leave tomorrow...

sramelyk · Jul 6, 2005

Re: Radio Shack Rectifier and heat?

I looked threw some old posts and note that a heatsink is needed.. So.. What size? One about the size of the rectifier? An old processor heatsink?

Ben Konopacky · Jul 6, 2005

Re: Radio Shack Rectifier and heat?

Don't forget to apply heat sink compound to tramsfer heat to mtg. base.

Silvertip · Jul 7, 2005

Re: Radio Shack Rectifier and heat?

Use as big a heat sink as you can possibly fit under the hood. The sink itself should be bolted somewhere on the engine so the sink can transfer the heat.

sramelyk · Jul 7, 2005

Re: Radio Shack Rectifier and heat?

Ok.. I will get one today.. Whats the worst outcome of this? The rectifier exploding? Or just blowing the rectifier and it not working? We are going camping for 3 days, and I am worried now.. The charging system hasn't worked for the last 2 years and am wondering if I should just disconnect it for the weekend.. Thanks for the help!

phatmanmike · Jul 7, 2005

Re: Radio Shack Rectifier and heat?

stop telling this guy he needs a heat sink! who said this, or who here uses a heat sink? i personally have used these on more than 6 different motors, two i still currently own. yes they get hot, thats fine, dont shove em down your pants when they are hot and youll be fine.

sramelyk · Jul 7, 2005

Re: Radio Shack Rectifier and heat?

Welp.. That makes me feel better.. I would really like some concensus.. Just worried about the family..

achris · Jul 7, 2005

Re: Radio Shack Rectifier and heat?

If you're really concerned about the heat, bolt it to the engine block. That'll get rid of more heat than you can generate. Chris.......

sramelyk · Jul 7, 2005

Re: Radio Shack Rectifier and heat?

Can't seem to get any holes to line up right.. That was my first thought, and really not because of heat but just to have it mounted down tight.. I am not really concerened with the heat as long as its not going to explode.. I ran it at about 2000 rpm's last night for about 15 minutes and it never seem to continue to get hot.. Reach a certain temp then seemed to maintain that temp. I would assume however that it would get hotter at higher rpms.. Normally I would just buy a heatsink, and attach it.. Unfortunately I just don't know if I have enough time.. I am at work and my boat and truck are loaded for camping.. I am leaving directly after work.. As long as I am not in danger, I feel fine.. If the rectifier just stops working I am fine, because thats were I have been for 2 years.. I just don't want the thing to explode and start a fire.. Which I guess anything is possible.

sramelyk · Jul 7, 2005

Re: Radio Shack Rectifier and heat?

myoutboards or anyone else.. Does anyone have one of these rectifiers on a boat with no heatsink? I would assum myoutboards does from his comments. Not sure if it was mounted to the block though.

Silvertip · Jul 7, 2005

Re: Radio Shack Rectifier and heat?

Yes some do have have a heat sink. Some are mounted in a cavity in the engine block and are water cooled. 20 amps makes heat. No -- it won't explode. Will it get hot enough to burn up some wires touching it or chaff things by bouncing around and leaving one stranded is questionable. Its a suggestion -- not a demand. If rectifiers and regulators were cooled better, you would not see the number of failures you do on these boards.

sramelyk · Jul 7, 2005

Re: Radio Shack Rectifier and heat?

Fair enough.. I thank everyone for the help and suggestions.. I am going to give it a whirl and hope for the best.. If it survives the weekend I will put a heatsink on for good measure when I return. I really appreciate all the help I have received here on iboats.com. What an invaluable resource!

JasonJ · Jul 8, 2005

Re: Radio Shack Rectifier and heat?

When I did mine, I cut a piece of scrap aluminum into a 3x3 square, and mounted the whole mess where the old rectifier was. I have had no problems. The heat sink is a better-safe-than-sorry, not an absolute necessity.

Nos4r2 · Jul 8, 2005

Re: Radio Shack Rectifier and heat?

could always try using an old PC CPU heatsink.... they are free down at the rubbish dump!

CARLOS · Jul 27, 2005

Re: Radio Shack Rectifier and heat?

Sramelyk: I would like to ask you if I can install any rectifier to my 2.5L engine, because I concluded that one of the rectifiers are bad. RPM¨s are working but same voltage at any engine speed. So, how can I install a Radio Shack rectifier in my engine? It´s cheaper than the original Mercury rectifier? In my country I can find Radio Shack Shop... Please explain to me how can I solve this problem with foreigner rectifier! Thanks Carlos Schemel Venezuela

JasonJ · Jul 27, 2005

Re: Radio Shack Rectifier and heat?

Carlos, all you do is hook up the two stator wires to each A/C post, the red positive wire to +, and ground the - post to the engine on those 'shack rectifiers. All a rectifier is is a diode that clips the alternating current from the stator, causing it to only flow in one direction, (DC Current). All rectifiers do it the same way. The 'shack rectifier can handle the output of any outboard motor stator.

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