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  1. #1

    Default 40hp yamaha (c40tlrw) rectifier location

    I goofed up yesterday and crossed the wires installing the battery after winter storage. Power trim and starter went dead. I found the blown fuse and replaced it so now the motor starts and trim works but the battery voltage stays at 12volts after the motor starts. My guess is I took out the rectifier and probably won't be able to charge the battery. Can anyone tell me where the rectifier is located on a 1997 40hp yamaha.
    Or where most are located for that matter. I found some rectifier pictures on the internet and nothing like that jumps out on my motor unless it's under the flywheel.
    teepster

  2. #2
    Join Date
    Jun 2011
    Posts
    107

    Default Re: 40hp yamaha (c40tlrw) rectifier location

    I've made the same mistake and I killed the rectifier. If you don't see it in plain sight it might be hidden under a cover. Here are some hints: It should have 2 wires from it to the stator which will deliver AC voltage to it. It should have a ground wire and a thick red wire go to it. The thick red wire goes to the battery and I believe it should go thru a fuse. Check this fuse before you buy the rectifier. My motor didn't have the fuse and therefore it fried the rectifier. Now I just put in a fuse to protect it. GL.

  3. #3

    Default Re: 40hp yamaha (c40tlrw) rectifier location

    I found it, thanks. On my 40 it sits right up on top just behind the starter. 2 greens a red and a black. I even removed the one bolt holding it in to get the part number off the bottom of the unit. Looks to be a cinch to replace other than maybe the black wire which is nestled underneath in a small dungeon but I'll can get it. My fuse was blown but I still think the rectifer/regulater went anyway. I get 12 volts with the key off and the exact same with the engine running. Seems like it ought to be at least 13v running even with a well charged battery. My neighbor at the lake has the same motor so I can meter his to check for proper behavior before ordering a new one. Rectifier prices on the internet (6h2 81960) run between $80-$120 depending on the website and shipping. Boy O boy that can make a man feel stupid.

  4. #4
    Join Date
    Jun 2011
    Posts
    107

    Default Re: 40hp yamaha (c40tlrw) rectifier location

    Hey,
    Stick the meter to the hot terminal on the rectifier. Check the voltage there. If it's 12V, then the rectifier is dead. You might get lucky because the fuse supposed to protect the rectifier. I got lucky with mine and payed $50 lol. It's still an expensive lesson. GL

  5. #5

    Default Re: 40hp yamaha (c40tlrw) rectifier location

    I get 12v across the battery whether it's running or not, even at high idle. My lake neighbor tested his (same motor) and stayed at 12v while idling until he increased the idle and he went to 12.8v. I checked the red lead coming off the rectifier and it's a straight shot to the pos. lead on the battery so that should be the same as reading at the rectifier itself. I think I need to go rectifier shopping.

  6. #6

    Default Re: 40hp yamaha (c40tlrw) rectifier location

    I'll take the time to go over the final results of the problem encountered when I crossed the battery connectors by mistake on my 1998 40hp yamaha. The power trim would not work and turning the starter key did nothing. I found the main protective fuse that comes off rectifier was blown. My motor had a spare 20A fuse hung off the line. I replaced the fuse and the power trim was working again and the engine started. From what I read there still was a chance the rectifier was a goner. Once I got my hands on a good volt meter that reads in the tenths and a known good motor to compare to (my neighbors) I found my r
    rectifer (charging circuitry) is OK. The battery reads 12 volts when off and at slow idle and as idle was increased the battery voltage moved up to 12.8volts just like my neighbors. I'm comfortable that everything is properly again thanks to the fuse and I got lucky after a stupid senior moment. Thanks to all those who input into these forums. They are a God send for all us DIYers who want to save a few bucks.

  7. #7
    Join Date
    Jun 2011
    Posts
    107

    Default Re: 40hp yamaha (c40tlrw) rectifier location

    That's good news. The reason my rectifier burned because the previous owner put a big jumper between the Battery cable to the hot side of the rectifier. This basically bypass the fuse. I have removed this jumper and the motor runs fine now. However I will make sure I take my time putting on one battery terminal at a time from now on.

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