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  1. #1

    Default New to Outboards need a little help with My Merc 175

    Hey guys and girls. I recently picked up a boat with a 175hp 2 stroke Mercury Racing oil injected motor. (oil injection is disconnected and oil is just mixed in the gas) I have no Idea what year (older) as it doesnt have a serial number sticker. (motor was repainted at one point). I am a gear head but I am a noob when it comes to outboards

    First things first. Any where else where I can check to find the serial number stamped?
    Next. I got it running great out of the water with a garden hose hooked up to it. Went to put it in the water and went for a nice ride. Motor wont go wot. Without the motor running you can floor it and the throttle linkage all moves and opens the throttle blades up all the way. In the water when you floor it it doesnt seem like it wants to open up. What could be going on here?
    Next. How do I hook a tac up to it as I have no idea what rpm the motor is running? The boat has a tac but I dont see any wires from the tac going to the motor. Where do I hook it up at the motor?
    After going for a ride when the motor heats up at low rpm / speeds it runs a little rough. I was planning to change all the plugs to see if that helps (has surface plugs in it) any other ideas here?


    Thanks for all the help. I will post some pics tomorrow!

  2. #2
    Join Date
    Sep 2010
    Posts
    17,426

    Default Re: New to Outboards need a little help with My Merc 175

    Does spark jump a gap of 3/8" on all leads.----Sounds like it is running on 3 cylinders.----And yes it will " bark and roar " and sound great on a hose on 3 of 6 cylinders.

  3. #3

    Default Re: New to Outboards need a little help with My Merc 175

    Quote Originally Posted by racerone View Post
    Does spark jump a gap of 3/8" on all leads.----Sounds like it is running on 3 cylinders.----And yes it will " bark and roar " and sound great on a hose on 3 of 6 cylinders.

    I will test that today. I am new to surface plugs so wasnt sure how to test or what to look for with them. That sounds about right only running on half they cylinders. On the test ride it if I had it under throttle and hit a wave the sound of the motor would change like it started running better but it didnt change the speed of the boat
    Last edited by Anythingcanhappen; 08-13-2019 at 09:35 AM.

  4. #4

    Default Re: New to Outboards need a little help with My Merc 175

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  5. #5
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    3,527

    Default Re: New to Outboards need a little help with My Merc 175

    Its a Frankenmotor...it a Generation1 2.0L block on a 1984 midsection. If a 175 block it has a different exhaust and if adapter plate wasn't changed it will suck water in the bottom 2 cylinders.
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  6. #6

    Default Re: New to Outboards need a little help with My Merc 175

    Quote Originally Posted by faztbullet View Post
    Its a Frankenmotor...it a Generation1 2.0L block on a 1984 midsection. If a 175 block it has a different exhaust and if adapter plate wasn't changed it will suck water in the bottom 2 cylinders.

    Can you please explain? No idea what you mean. How can i check / what should I look for? If it was sucking water into the bottom 2 cylinders doesnt that mean it wouldnt run at all or hydro lock when I had it in the water?

  7. #7
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    3,527

    Default Re: New to Outboards need a little help with My Merc 175

    1) Gen1 blocks have no casting for oil injection pump....yours don't either so it old style motor.
    2) Its had newer 80's components added on. Most likely a 84 150 that blew and a old style powerhead installed.
    3) If it is a 175 block the exhaust ports will not match up and will water intrude the bottom cylinders (milky/water drops) on plugs
    4) Look on block behind throttle arm and date will be stamped on it plus where block halfs meet it will be stamped with a 7 for 175, 5 for a 150
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  8. #8

    Default Re: New to Outboards need a little help with My Merc 175

    Quote Originally Posted by faztbullet View Post
    1) Gen1 blocks have no casting for oil injection pump....yours don't either so it old style motor.
    2) Its had newer 80's components added on. Most likely a 84 150 that blew and a old style powerhead installed.
    3) If it is a 175 block the exhaust ports will not match up and will water intrude the bottom cylinders (milky/water drops) on plugs
    4) Look on block behind throttle arm and date will be stamped on it plus where block halfs meet it will be stamped with a 7 for 175, 5 for a 150


    Awesome that is some great info! So it does have a 5 so its a 150 block. So that means I really have a 150hp motor here? someone just put the 175 cover on it? I did look at all the plugs and the bottom two showed no signs of water in the cylinders.
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    Also what is this thing?
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  9. #9
    Join Date
    Nov 2011
    Location
    tennessee
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    Default Re: New to Outboards need a little help with My Merc 175

    Yes its a 150 with 175 decals...look behind that arm on block and you will see date made. The "can" is your enrichener .
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  10. #10

    Default Re: New to Outboards need a little help with My Merc 175

    Quote Originally Posted by faztbullet View Post
    Yes its a 150 with 175 decals...look behind that arm on block and you will see date made. The "can" is your enrichener .

    The top of the flywheel says v175. Im just trying to confirm what I have and be able to order parts for the correct motor if I need to.

  11. #11
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
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    Default Re: New to Outboards need a little help with My Merc 175

    If you need parts order/look up 1986 150hp parts, If you need block parts lookup 1977-80 ser#4868998-5503246. Its a 150 .....
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  12. #12

    Default Re: New to Outboards need a little help with My Merc 175

    Quote Originally Posted by faztbullet View Post
    If you need parts order/look up 1986 150hp parts, If you need block parts lookup 1977-80 ser#4868998-5503246. Its a 150 .....

    Thanks for all your help/info!

  13. #13

    Default Re: New to Outboards need a little help with My Merc 175

    Quote Originally Posted by faztbullet View Post
    If you need parts order/look up 1986 150hp parts, If you need block parts lookup 1977-80 ser#4868998-5503246. Its a 150 .....
    Can you please help me with the correct part number for coil packs and plug wires for this motor? Motor still has a slight miss at low rpm / low throttle. Going to change those all out.

    Also what can be a reason why I cant get it to start when its cold. In neutral I pump the throttle a few times and it still wont fire. Fires right up with a little starting fluid or when it warm. Its weird the motor will run great at a steady rpm say 20mph for like 5 minutes but the second you change throttle position its like the motor has a brain fart. also when taking off from idle if you pin it sometimes it will take off right away and do great other times its like a delayed response takes a few for it to make up its mind then it finally will go wot

    any help would be appreciated

  14. #14
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
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    Default Re: New to Outboards need a little help with My Merc 175

    1) get you a manual
    2) pumping throttle does nothing unless engine is running......then it will raise/lower RPM
    3) pump bulb till hard, push in on key while cranking to choke it....hold in till hits and runs.
    4) DO not use starting fulid as washes oil out of engine!!!
    5) Compression test!!!
    6) sync and link
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  15. #15

    Default Re: New to Outboards need a little help with My Merc 175

    Quote Originally Posted by faztbullet View Post
    1) get you a manual
    2) pumping throttle does nothing unless engine is running......then it will raise/lower RPM
    3) pump bulb till hard, push in on key while cranking to choke it....hold in till hits and runs.
    4) DO not use starting fulid as washes oil out of engine!!!
    5) Compression test!!!
    6) sync and link

    There it is. I knew there had to be a choke built in somewhere. Im use to a 454 with manual choke with the throttle lol
    I did a compression test all cylinders were within 10% of each other. Also Installed new plugs. Still has the slight miss as low rpm/throttle.

    so a 1986 v150 manual will be the correct one right? Also any manual I find online is asking for serial number which I dont have so I am not sure.
    sync and link?

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