Motor Help (50 Hp Merc 2 Stroke)

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Thread: Motor Help (50 Hp Merc 2 Stroke)

  1. #1
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    Motor Help (50 Hp Merc 2 Stroke)

    2003 Mercury 50 Hp 2 Stroke. This motor gets used and has never set up for more then a few weeks at a time and fuel stabilizer is used when it is going to set for more then a couple weeks. I will change in-line fuel filter and plugs this weekend but i have a feeling something worse has happened. Running full throttle (5800 rpm's) across the water Wednesday night and just all a sudden boat bogged down and now will not reach over 3000 rpm's while under load. In natural it will still rev up like normal,motor now has a skip while at idle but will run from idle to 3000 rpm's like normal then just act under powered and stay at this speed. Wondering if this motor has a low and high speed stator and the high side burnt out causing this issue's? Also need to know how to check compression on the 3 cylinders to see if i have dropped one? Any advice can be used now before i bust into it or take it to some one and spend a fortune. I have already done a good bit of searching on some boating forums (useless) and i want to say we still have the best group of folks on the web when it comes to help, replies and just good ole fun.

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  3. #2
    Hoopty's Special someone
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    You can buy a compression guage at any good auto parts store for about $35. Just take out all the plugs, screw the gauge into each cylinder (one at a time), turn the key for a few seconds and see where the gauge locks. Release gauge and do all 3 cylinders. They should all be within 5% of each other........probably around 110-120 (that is a guess based on my 2002 3cyl merc 75hp).

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    Quote Originally Posted by Delta Dog View Post
    You can buy a compression guage at any good auto parts store for about $35. Just take out all the plugs, screw the gauge into each cylinder (one at a time), turn the key for a few seconds and see where the gauge locks. Release gauge and do all 3 cylinders. They should all be within 5% of each other........probably around 110-120 (that is a guess based on my 2002 3cyl merc 75hp).
    Will the pressure gage have different ends with different thread patterns or are most motor the same.

  5. #4
    i would check the compresion first but could be a cloged jet in the carb it still happens even with fuel stabil

  6. #5
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    Quote Originally Posted by Midnight Sun View Post
    i would check the compresion first but could be a cloged jet in the carb it still happens even with fuel stabil

    I hope it to be something small and not a dropped cylinder or the stator. BUT with my luck we will see.

  7. #6
    yea they come with adapters in the kits u buy bought mine at harbor freight around 25 bucks

  8. #7
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    Quote Originally Posted by Midnight Sun View Post
    yea they come with adapters in the kits u buy bought mine at harbor freight around 25 bucks

  9. #8
    Hoopty's Special someone
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    Around here you can have a full diagnosis done for about $55. They check all the engine stuff and pressure test the lower unit, then make recommendations on what the problem is along with a quote to fix. After that you can haul it away and fix your self or get competitive quotes. All I am saying is $55 can be a lot cheaper than guessing and throwing parts at it.

    I am getting my 3 carbs rebuilt ($50 each) and new lower unit seals ($40) this spring. Not really having any major problems but this motor has never seen any mechanical maintenance and it is starting to hesitate on take off and the rebuild/repair cost seems cheap to me. Oh........and here, they don't charge the $55 diagnosis if they work on your engine........even better for under $200.

  10. #9
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    Quote Originally Posted by Delta Dog View Post
    Around here you can have a full diagnosis done for about $55. They check all the engine stuff and pressure test the lower unit, then make recommendations on what the problem is along with a quote to fix. After that you can haul it away and fix your self or get competitive quotes. All I am saying is $55 can be a lot cheaper than guessing and throwing parts at it.

    I am getting my 3 carbs rebuilt ($50 each) and new lower unit seals ($40) this spring. Not really having any major problems but this motor has never seen any mechanical maintenance and it is starting to hesitate on take off and the rebuild/repair cost seems cheap to me. Oh........and here, they don't charge the $55 diagnosis if they work on your engine........even better for under $200.
    You are correct cause i can easily tare up more then 55 worth of stuff in a short amount of time. LOL
    I am going to change plugs, in-line fuel filter and check compression the off the shop it will go after that probably.

  11. #10
    Gator Gar
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    make sure the water pump is pumping good....turkeymansc had the issue at our gwood tourney last year and he said his water pump was not pumping a full and the motor wouldnt run but about 3000 rpm...his is a yamaha 75hp...

  12. #11
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    Quote Originally Posted by scriverrat View Post
    make sure the water pump is pumping good....turkeymansc had the issue at our gwood tourney last year and he said his water pump was not pumping a full and the motor wouldnt run but about 3000 rpm...his is a yamaha 75hp...
    Water pump is only a year old and seems to be pumping strong. But will double check during test run after plugs and filter change.

  13. #12
    Gator Gar
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    I don't know about Mercs but my Johnson will shut it self down if it sences its not getting enough water.I bet you just have a chuck of crap in one of the jets in one of your carbs.My 50 johnson picked up a small piece of something last summer and did the same thing your talking about.It would rev up in netral but under a load it would barley pull itself.If your nor scared to take your carbs off i would just pull one off at a time a give them a good sprayin down with some carb cleaner.It doesn't take a very big piece to pull them off.

  14. #13
    or a can of carb fogger for ur local boat shop will work wonders and dont have to remove the carbs try a can of sea foam in ur tank also its a cleaning machine dose the whole motor internaly

  15. #14
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    Quote Originally Posted by kskiller View Post
    I don't know about Mercs but my Johnson will shut it self down if it sences its not getting enough water.I bet you just have a chuck of crap in one of the jets in one of your carbs.My 50 johnson picked up a small piece of something last summer and did the same thing your talking about.It would rev up in netral but under a load it would barley pull itself.If your nor scared to take your carbs off i would just pull one off at a time a give them a good sprayin down with some carb cleaner.It doesn't take a very big piece to pull them off.
    Will do thanks.

  16. #15
    Mudfish
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    Also check your fuel lines. If there is a little tear where it can get air in the line will make it do that to. Also check your cap on the tank it might not vent enough. Even though it idles up fast in neutral does not mean its using the same amount of gas as wot.

  17. #16
    Gator Gar
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    Its not really likely that you just suck up a piece of trash if the engine was running well across the water and then just acted up.

    Do you use Non-ethanol fuel?
    How long had it been since the engine had been run before the time it acted up?

    Note: Its cheap insurance to use stabil at every fill up.

    Note: Be sure to pull your kill switch before doing a compression check. Also, do it at wide open throttle at at least with the high idle lever all the way up.

    Note: After eliminating the compression, spend a few bucks on a spark tester from the parts store. Lisle makes a decent one that will attach in line between your plug and coil wire. It will flash if you have fire. Check every cyl by doing one at a time with the engine running on the garden hose.

    If you have a skip, its most likely caused by either loosing fire to one particular cyl, or a major mechanical issue. Compression check and spark check will answer that question.

  18. #17
    Mudfish
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    Sounds like carb, does it have one or 3?....could be linkage......could be cracked fuel pick up in tank....I know you probably aint feelin it, but if you are willing, you can bring it down and throw it in the garage Saturday and we'll drink beers and check er out.



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