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Ford – Gustavson, where is the calorstat on a 2712

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    Dr Jorg Taubel

    While servicing my 1977 Ford 2712 that powers my NC33 I wondered whether the engine is equiped with a calorstat (that part that open when a certain temperature is reached in order to allow cooling water to cool down the top part of the engine).
    According to Ford service manual the calorstat seats on the top of the engin, at the front left corner, just under a rubber pipe that was removed  with Gustavson marinisation. This original sitting is actually just under the addeed cast iron bowl that comes <ith Gustavson marinisation (the bowl into which one will add water plus glycol when topping up).
    Should this be the case, is there any special precaution to remove this bowl in order to gain access to the calorstat.
    Any special indications about calorstat type and availability ?




    I just see your question now (june 15th). I’ll be back on board next week, and reply to you. If I forget (I currently have bad time with my maxprop propeller) please send me a reminder :
    Dr Jorg Taubel

    Hello Joel,

    For your information, someone on Nautcat US forum kindly sent me a copy of that part of the Gustavson marinisation drawings that relates to the water tank tlocated at the front end of the 2712.
    From that drawing it is clear that the calorsat is under the tank, roughly located above number 6231 on the drawing . One has to remove the two long screws 20030 to get access to it.
    The drawing also shows the two anodes 6206 and 6258 tha have to be periodically checked and replaced.

    By the way, I would love to find the other drawings of the gustavson marinisation.


    Some news to close this issue.
    I eventually acquired a genuine Ford thermostat/calorstat (number 815F 8575 AAA) from the french 271x Ford dealer, namely Fornaut, in Le Pré Saint Gervais.
    Cost for it was around 25€ plus extra 2,7€ for paper gasket, VAT incl.
    They confirmed the exact location of the thermostat at the top left front of the engine seen from the inverter.
    The recommended a “start to open at 71 °C” version for a marine engine and they recommended tIat I cut and remove the somewhat movable restriction (copper part, at 3 hours on the attached picture) in order to ease cooling flow.

    Their courtesy was to supply me with a pdf version of the 271x 1975 service manual, in french, which may prove unvaluable while undertaking services. Please drop me a note if you like a copy of it. Richard, do you thing it has it’s place in the association repository ?


    Just purchased a N33 1978, Ford 2712E Gustavson marinised, and found this thread very helpful despite being so old. Thank you to all contributors.

    Hence, just in case someone will be searching the forum for thermostat issues, I would like to share my recent experience. The Ford maintenance manual specifies 82C for standard type thermostat (not high flow). A 74C could be used if motoring in waters warmer than UK waters (ASAP Supplies suggestion).

    In the attached photos:
    – Header tank
    – Header tank removed and thermostat visible to centre left (rust covered circle)
    – Thermostat removed and cleaned.
    – Ford maintenance manual notes on thermostat.

    On testing in a pan full of water, the thermostat started opening at around 80C, and fully open at 97C, just before boiling point. Spot on with Ford manual, apart from some measurement errors from my meat thermometer!


    In order to add new spare belts waiting for the operational one to dismantle/explode (a very poor design by Ford) I had to remove to water tank under which is located the calorstat.I took some notes and annotated some pictures (in french langage, vase-expansion_5991.jpg) that may be of help.
    – water tank (where one add water+glycol) is located on the front end of the motor (almost under the steering wheel on an NC33), picture is vase-expansion_5991, calorstat is right in the middle, with two long screws adjacent to it
    – tank is held by two long screws (“tiges de fixation du vase d’expansion”) around the calorstat location, one has to remove those.
    – tank is held on the port side by two nutts , just remove the most accessible one (see vase-expansion_20210707, “écrou à déposer”)
    – there is a black 43 mm rubber pipe under the tank that connects to a steel pipe that runs in front of the water pompe (see “Moteur Av Refroissement”, item marked “durit du circuit d’eau douce”)
    – from my experience it is safer to disconnect the bottom serflex necklace (the one closer to the steel pipe) than the two ones just under the tank (détails in 20210919_204554). When reinstalling the whole thing you will just have to succeed inserting the 43 x 80 mm black rubber pipe bazck into the steel pipe. Dismantling the rubber pipe form the top turns into a nightmare to reinstall. Details in 20210919_204554
    – you may have to dismantle the transparent exit pipe on the port side (so called “tricot eau de mer” on my global picture
    vase-expansion_5991, it best to avoid that.
    – you may have to unscrew the ‘serflex necklace’ on the small black rubber pipe that connects (incoming seawater) to the starboard side of the oil radiator (labelled “arrivée EdM dans l’échangeur” in “Moteur Av Refroidissement_0512”)
    – Then just lift the whole soft water tank to access the calorstat. Rinse and clean it and its bedding, test it (it not not be bad), install a new paper gasket (not critical ?), reinstall the whole thing and test for leaks.
    – I found myself having to use some lever or rope to move the steel pipe upward into to 43mm black rubber pipe connected to the tank. No other difficulties found. The entire process took me 1 to two hours, but I did it three times (ventilator belts are awkward)

    Apologies for this too long and cumbersome message.

    Yves (Naila of Burnham, NC33 # 488)


    That’s brilliant Yves, thank you.
    Could you send me a web link to a spare alternator belt I can purchase that would fit my Nauticat 33 MK2?


    Relating to alternator belt that suits my NC 33 Mk 2 # 488 (77-78) the previous owner advertised me to have “standby spare” belts in place.
    Prior to selling I had a mecanic install a Motaquip VBF252 as a spare
    Previous owner notes advocated Misuboshi REL 13×1120
    Aboard was one “Motaquip VBF252” as a spare and also one “Roflex A45 13×1143 (50)”
    Full description for Motaquip is “VBF 252 12,5 x 1125 M”
    Full description for Mitshobishi might be 13 x 1120 A”
    Full description of Roflex is “A 45 13X1143 50”

    Those references should suit for a normal Ford 2712 with standard mouting and actually they also suit my new mounting (see below)

    Personnal dimension onboard my MkII # 484
    Two years latter, while replacing a dead alternator I broke the screw that attaches the “belt tensioner” to the engine (see picture). I had to install that screw to another empty place little more up and a little more toward the middle of the engine, roughly 3-4 cm from the original one and I also had to remanufacture a “belt tensioner”. Thus my measurement are slightly modified (though Motaquip and Roflex are still almost OK with the new belt tensioner)

    For my non stanadard mouting, a “Gates 6475MC” (AVX13 X 1125 La) will not be long enough. a “Gates 1277MC” (AVX13 X 1175 La) is perfect

    I had to learn that the dimension of a belt (external circumference) depends upon the shape of its section (so called “trapezoidal”), depends upon the external outside width of the belt (13 cm, though 12,5 seems OK and 12,85 mm was the value of one of my operational one). I noticed that they break every 5 years (500 to 600 hours)
    I came to the conclusion that the value ot the circumference lies between 1125 and 1190 and I found no other way than trying …
    And also that the tensioning must be sufficient that twisting (in order to inspect the inside side of the belt) the installed belt by 180° is barely feasible though feasible.

    Hope it helps.
    Feel free to further contact me.
    Yves (Naïla of Burnham, NC33 Mk II # 484 1977-1978)


    Thank you Yves, that’s brilliant. Well done with your modifications.
    I have ordered a cogged Gates 1125mm and see how that fits before reinstalling the header tank.


    Should the 6475MC be fine, I advise you to install an extra spare one tied to the iron and rubber pipes.
    Next time the operational belt breaks, in 5 roughtly 5 years from now, itwill save you a lot of time desinstalling and reinstalling the water tank.
    This is an advice I got from the previous owner and that I luckily followed.


    Great advice Yves! Thank you so much for passing it on. Will certainly do as you suggested.


    Does anyone have the drawings of the Gustavson expansion tank and lub oil cooler arrangement for my 1982 MkII 33


    I see you have a drawing of the Gustavson header tank, could you please send me a copy as the heat exchanger on mine is leaking and I would like to if it could be retubed.

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