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  1. #1
    Join Date
    Jan 2012
    Location
    East Sussex
    Posts
    7

    Default MD22 Raw pump cam drive wearing

    Hi

    We have an 1990 MD22 engine. The sea water pump is driven by a cam which goes into a slot on the shaft of the pump assembly. Several times in the last 14 years the slot has worn - on one case enough to cause the pump to fail. The cam has also worn.

    The pattern of wear suggests that the cam is not going deep enough into the slot. The slot is about 8mm deep and when assembled the cam only seems to go into about 5mm.

    Between the engine and pump is a water pump flange which obviously affects the spacing but as far as I know there is only one of these.

    Has anyone else had this? We could fix it by making a 2-3mm flat to fit behind the cam (which attaches to the cam shaft with 3 allen bolts) but this seems strange. May be just bad design.

    Thanks

    Paul
    Paul Redstone

  2. #2
    Join Date
    Jan 2011
    Posts
    4,965

    Default Re: MD22 Raw pump cam drive wearing

    You could replace the pump with one from the turbo model, which is belt driven from a pulley on the back end of the camshaft. You can get the whole thing (including the mounting bracket) from Jabsco.

  3. #3
    Join Date
    Nov 2008
    Posts
    6,352

    Default Re: MD22 Raw pump cam drive wearing

    Cam?

  4. #4
    Join Date
    Feb 2003
    Posts
    14,457

    Default Re: MD22 Raw pump cam drive wearing

    Quote Originally Posted by Bobc View Post
    You could replace the pump with one from the turbo model, which is belt driven from a pulley on the back end of the camshaft. You can get the whole thing (including the mounting bracket) from Jabsco.
    My naturally aspirated one from 1999 has the belt drive as well. The op is using the wrong terminology, it isnt a cam it is a slot and tang which fits in to the slot. IIRC there is a tool to align these bits when assembling the pump on to the cam shaft.
    Last edited by skipper_stu; 04-11-18 at 17:17.

  5. #5
    Join Date
    Jun 2001
    Location
    UK East Coast
    Posts
    1,487

    Default Re: MD22 Raw pump cam drive wearing

    Quote Originally Posted by PaulReds View Post
    Hi

    We have an 1990 MD22 engine. The sea water pump is driven by a cam which goes into a slot on the shaft of the pump assembly. Several times in the last 14 years the slot has worn - on one case enough to cause the pump to fail. The cam has also worn.

    The pattern of wear suggests that the cam is not going deep enough into the slot. The slot is about 8mm deep and when assembled the cam only seems to go into about 5mm.

    Between the engine and pump is a water pump flange which obviously affects the spacing but as far as I know there is only one of these.

    Has anyone else had this? We could fix it by making a 2-3mm flat to fit behind the cam (which attaches to the cam shaft with 3 allen bolts) but this seems strange. May be just bad design.

    Thanks

    Paul
    I have just overhauled the raw water pump, including a new pump shaft, on my VP engine. Different engine to yours but the raw water pump has the same slot in the end of the shaft. When pressing the new pump shaft into the bearings there is no shoulder on the shaft that limits how far in the shaft goes so if you press it in too far you will have insufficient engagement of the drive into the slot. I managed to get the pump drawing (its a Johnson pump) which gives the dimension of the shaft projection beyond the mounting flange to ensure i had the correct engagement. If all this is applicable to your pump too, maybe someone previously overhauled the pump and did not press the shaft into the bearings correctly.

    Www.solocoastalsailing.co.uk
    Last edited by Plum; 04-11-18 at 20:46.

  6. #6
    Join Date
    Feb 2003
    Posts
    14,457

    Default Re: MD22 Raw pump cam drive wearing

    Quote Originally Posted by Plum View Post
    I have just overhauled the raw water pump, including a new pump shaft, on my VP engine. Different engine to yours but the raw water pump has the same slot in the end of the shaft. When pressing the new pump shaft into the bearings there is no shoulder on the shaft that limits how far in the shaft goes so if you press it in too far you will have insufficient engagement of the drive into the slot. I managed to get the pump drawing (its a Johnson pump) which gives the dimension of the shaft projection beyond the mounting flange to ensure i had the correct engagement. If all this is applicable to your pump too, maybe someone previously overhauled the pump and did not press the shaft into the bearings correctly.

    Www.solocoastalsailing.co.uk
    His wearing is being caused by the mis alignement of the tang and slot. Most of the time its ok but a tool is needed to line it up. https://www.manualslib.com/manual/84...age=102#manual
    Last edited by skipper_stu; 05-11-18 at 09:41.

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