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  1. #1

    Default Please help a noob to connect water pressure gauge

    Hello,
    I have bought 40 hp 4 stroke Tohatsu last year ( the motor is 2021 I think), installed it earlier this year and got stuck with water pressure gauge 3GL725980M installation on the motor side. It came with the paper instructions with black/white picture and I simply can not figure out which part of the motor is pictured. Never had large outboard before.
    I can not find any instructions on the web so all I have is this picture (attached).
    It very well may be that the T-fitting goes into pissing tube but I would rather ask someone who knows what they are doing before cutting the wrong tube.
    Any help would be greatly appreciated. If someone has a similar motor and could send a photo of the engine part pictured in the installation instruction that would be ideal. Thank you for your help.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  2. #2
    Join Date
    Mar 2010
    Location
    Hamburg, NY, USA
    Posts
    3,446

    Default Re: Please help a noob to connect water pressure gauge

    Those instructions are for a TLDI motor. You have an MFS40A most likely. Year is irrelevant; model is everything. I have never seen a need for that 10 psi gauge. But it's doubtful the pee tube will have any measurable pressure. They usually install near the thermostat housing.
    Paul
    Certified Tohatsu TLDI Technician
    Hamburg, NY USA

  3. #3

    Default Re: Please help a noob to connect water pressure gauge

    Quote Originally Posted by pvanv View Post
    Those instructions are for a TLDI motor. You have an MFS40A most likely. Year is irrelevant; model is everything. I have never seen a need for that 10 psi gauge. But it's doubtful the pee tube will have any measurable pressure. They usually install near the thermostat housing.
    Thank you, sir.
    That is correct, I have MFS40A. I looked up on Tohatsu US website and it says this gauge is compatible with MFS40/50 and all tldi models. The instruction lists only MD 30B2/40B2. I suspect MD models are for EU market, at least this is what the manual says for those models.
    With all this said, maybe you could advise what side of the motor is pictured? To my shame I do not know how air rail looks ( or exhaust cover) and can not find any meaningful schematics. Thank you.

  4. #4

    Default Re: Please help a noob to connect water pressure gauge

    Also found this on the website selling the gauges INSTALL T-FITTING IN EXHAUST TO RAIL HOSE*/}*

  5. #5
    Join Date
    Mar 2010
    Location
    Hamburg, NY, USA
    Posts
    3,446

    Default Re: Please help a noob to connect water pressure gauge

    I would call Tohatsu America in Dallas to ask where the best place would be to connect the gauge. Why do you want the gauge, anyway?
    Paul
    Certified Tohatsu TLDI Technician
    Hamburg, NY USA

  6. #6

    Default Re: Please help a noob to connect water pressure gauge

    Thanks, I will do that. IDK, when I was looking at gauges figured that this one would be useful, have been boating for a couple of months without it . It is set up on the console, just the tube on the motor side is not connected and it bothers me a lot.

  7. #7

    Default Re: Please help a noob to connect water pressure gauge

    Got the reply from Tohatsu, "T" goes into pissing tube, just a couple of inches above discharge hole. Installed, will check how it works.

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