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  1. #1

    Default 1978 40 hp mercury

    Hello everyone, this is my first post here . Looking to get some help. I just purchased a 1978 Bass tracker with 1978 40 hp mercury. I started it last night with muffs on and no water came out tell tale. Previous owner says he replaced water pump in July and showed me the receipt where he had indeed bought a water pump. My question is does this model have a thermostat of any kind . Serial # is 5174633. Thank you for your help and if you can direct me to a good online parts place I would appreciate it. What manual is best for reference?

  2. #2

    Default Re: 1978 40 hp mercury

    Since you have the serial number, you might be able to use the engine parts section of this forum to see a parts breakdown; my '92 Merc 40 has no thermostat; I have bought parts for it from marineengine.com. Have emailed them with questions and have gotten quick responses. If you can get your hands on a shop manual for it, that would be priceless.

  3. #3

    Default Re: 1978 40 hp mercury

    I tried putting in my serial number and it says is doesn't exist?

  4. #4

    Default Re: 1978 40 hp mercury

    The Mercury website does not go back that far. You have to manually look for your #. Check the pump make sure the key is in and the tube is lined up. And make sure there are no blockages in the pee-hole. Is this a 2 or 4 cylinder motor.
    Last edited by flyingscott; 09-12-2019 at 10:07 AM.

  5. #5

    Default Re: 1978 40 hp mercury

    Quote Originally Posted by flyingscott View Post
    The Mercury website does not go back that far. You have to manually look for your #. Check the pump make sure the key is in and the tube is lined up. And make sure there are no blockages in the pee-hole. Is this a 2 or 4 cylinder motor.
    It is a 2 cylinder. I pulled the pee hole line off, it is not blocked. On this model the pee hole line s part of the fuel pump assembly. my next step I to take fuel pump assembly off and see if there is any blockage there. I just didnt know if this engine had a thermostat or not. Thank you, for all the advise you can give me

  6. #6
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    16,277

    Default Re: 1978 40 hp mercury

    Disconnect and plug the water line going to the fuel pump--it's not necessary and cheats the power head of cooling water. Redo the hose coming from the top of the block and see if water shoots out. It should or...

    Jeff

  7. #7

    Default Re: 1978 40 hp mercury

    http://www.marineengine.com/parts/me...ru-5556229-usa Your motor comes up as a 79 model.

  8. #8
    Join Date
    Mar 2015
    Location
    Brandon, VT.
    Posts
    160

  9. #9

    Default Re: 1978 40 hp mercury

    Quote Originally Posted by flyingscott View Post
    I noticed that when I did the serial number check on here. Title says 78

  10. #10

    Default Re: 1978 40 hp mercury

    Quote Originally Posted by fastjeff View Post
    Disconnect and plug the water line going to the fuel pump--it's not necessary and cheats the power head of cooling water. Redo the hose coming from the top of the block and see if water shoots out. It should or...

    Jeff
    Are you sure this will cause no harm to my motor? I figure the engineer that designed it would have had a reason?

  11. #11

    Default Re: 1978 40 hp mercury

    Quote Originally Posted by Jim Marshall View Post
    Thank you

  12. #12
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    16,277

    Default Re: 1978 40 hp mercury

    Very few Mercs used the water cooled fuel pump (which destroyed most of the Merc triples out there--the impeller was too small to cool the top cylinders, that burnt up). Merc discontinued this dumb idea after a while, which should tell you something.

    Jeff

  13. #13

    Default Re: 1978 40 hp mercury

    Quote Originally Posted by fastjeff View Post
    Very few Mercs used the water cooled fuel pump (which destroyed most of the Merc triples out there--the impeller was too small to cool the top cylinders, that burnt up). Merc discontinued this dumb idea after a while, which should tell you something.

    Jeff
    Ok, so just reroute around fuel pump and straight to pee hole off block?

  14. #14

    Default Re: 1978 40 hp mercury

    The whole premise behind the water cooled fuel pump was that after hard running during warm weather and shutting the engine off, bumbles would form in the fuel pump chamber and cause a stall condition on restart and the engine would need to be re primed to continue running. The water cooling in the pump chamber kept the fuel from boiling in the pump and removed the stalling condition. Start the engine up on the muffs and put your hand on the water cover between the spark plugs and see if it gets too hot to touch. Those engines ran rather cold so if it gets hot to the touch there is an issue.

  15. #15

    Default Re: 1978 40 hp mercury

    As I thought after pulling lower unit the new water pump he put in in July was toast. It appears he ran the motor out of water as it had melted the plastic pump housing.

  16. #16
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
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    16,277

    Default Re: 1978 40 hp mercury

    Aaahhh! God protect us from "mechanics".

    Jeff

  17. #17

    Default Re: 1978 40 hp mercury

    Quote Originally Posted by fastjeff View Post
    Aaahhh! God protect us from "mechanics".

    Jeff
    aint that the truth! I tried to attach a picture from my phone but apparently im not that smart

  18. #18

    Default Re: 1978 40 hp mercury

    I have a 40HP EL 6E9 L 417558 Mariner outboard. I cannot find anything about this engine. I’m trying to buy parts. Does anyone know how to find the year or model #?

  19. #19
    Join Date
    May 2007
    Location
    Ireland,the only country in the world you can go North to go South
    Posts
    2,064

    Default Re: 1978 40 hp mercury

    Boatnewbie10

    1985 Yamaha/Mariner,but maybe start a new thread if you need anymore help.

  20. #20

    Default Re: 1978 40 hp mercury

    Sorry I’ve been trying to figure out how to start a new thread for an hour! Any help?

  21. #21

    Default Re: 1978 40 hp mercury

    I’m using an iPhone maybe the “new thread button” doesn’t show up.

  22. #22

    Default Re: 1978 40 hp mercury

    Quote Originally Posted by Boatnewbie10 View Post
    I’m using an iPhone maybe the “new thread button” doesn’t show up.
    Up toward the top left , blue square says + post new thread

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