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  1. #1
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    84 Mercury 2 stoke 150 rebuild

    What the heck I'm just gonna do it so don't roast me to bad gotta learn sometime right???

    I have a FREE 84 Mercury 150 (SN 6568987) that has low compression on 1 (55), 3 (88) & 5 (87), 2, 4 & 6 are 117-120. This is a learning experience for me, I've never been inside of the crankcase for pistons, rings, crank etc and need some guidance. I know there is little value to this engine so I'm going to try to revive it with new rings, wiring etc. The cylinder walls look fine (to me), no gouges or scoring I'm just going to hone it and put the new rings on the starboard (1,3,5) side I have a good head to go back on that side too. The ring on #1 came apart and pitted the head pretty bad, piston top looks fine as well. I know I need a complete gasket set and rings what else will I need to do this, any advise or should I ask along the way?

    I have the basic tools and I'm mechanically inclined...

    Do I need any special/specific tools to re-install the pistons?
    The stock needle bearings on the rods, keep what I pull out and reuse?
    Can I reuse the stock rod bolts/clips?
    Any brand better than the others for specific parts?

    What I'm looking at now:

    Mercury ring kit (2 per cylinder) 3.125" bore for 2.0 outboard 93481A12
    Mercury 78-90 2.0 Power Head Gasket Kit 27-90484A88
    240 grit Flex-Hone w/ 3.125" to hone the cylinder walls
    What else should I have on the order list?

    Thanks!

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  3. #2
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    I would suggest new rod bearings top and bottom. New top end bearing. If you choose to re use they must remain paired with original rod. Old bolts is a toss up. Definitely new clips. Pro marine sells parts and tools. You'll need pin tool. A ring compressor. I quit cleaning pistons and ring glands long ago. Should replace number one anyway. Replace any piston with loose ring locating pins. Pistons don't cost much. Worth considering anyway.
    That is/ was a tough engine. Chances are good the head gasket got it. Make sure the top of the bore is not eroded
    You are also gonna need reed/ manifold gasket. Pro sells the engine gasket kit. There is a special sealer for block halves you'll need to.
    Jim

    www.jrsperos.com

    10 Meter Fountain
    28 Skater

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  5. #3
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    Due to the fact this is a freebie and is 38 years old I would re-use everything you can. Be sure not to mix bearings. I put em in a baggie and label it. Above advice is fine for building a correct motor. Your's will not be correct without a bore job and a lot of new parts. It will however be a great learning experience that will prepare you for future motor projects. Pro Marine is the best source for the parts. Once you disassemble it clean the crap out of it and be diligent on assembly. No hurrying cuz that will bite you. You will most likely be surprised at the results. Might run for years but if it don't you will be able to figure out why. If at all possible rent or find a rigid hone to use. You'll have a ball and if you have questions or need advice you know the place to find it. Good luck and have some fun.

    Rock
    Team Junk

    No sparkling wiggles in here, only dump truck grinches.

    "Screamin Heathen"

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  7. #4
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    100% DO NOT use a flex hone! The balls can get caught in the ports or on the port edges & come loose or chip. Then you have abrasive pieces hiding inside your engine waiting to cause you misery. Get a factory manual & have fun. Those are tough old motors that run well almost forever.
    AIRWALK
    gettin' old ain't for sissies

  8. #5
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    Thank you for the info guys. I will be ordering most parts form pro marine usa and find their website easy to find what I "think" I need and prices seem reasonable. I guess when I start to disassemble the engine I can see if there was any other damage that will make or break the re-build.

    Roger that for the flex hone, that was one of my questions that was answered before I hit reply.

    I do have an original Mercury Service manual from my old XR6

    Dumb question... Can I leave 2,4,6 in the block (connected to the crank) and just hone 1,3,5 and do new rings and clips on the original pistons? Or just hone all 6 and do new rings and clips, because heck I'm already half way there... I don't want that to sound "cheap" but I don't want to bite off more than I can chew.

    What are the correct lubricants I should have on hand for reassembly?

    What is the special sealer for block halves, I assume pro marine sells it too?

  9. #6
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    I would say no to hone with pistons in other side. You will not be able to clean it properly. All the crude will need to be cleaned out of the ports in the block. Your success will largely be judged on how clean your work and assembly is.
    Needle bearing assembly lube for all bearings, 2 stroke oil on surfaces and bores. Acetone on head gasket surface. Don't even put finger prints on head gaskets.
    Sales guys are very helpful. They will have it. Not sure what the latest crank halves stuff is. It was Master gasket years ago . Got replaced by some new loctite product. Maybe some else will fill in that blank.
    Jim

    www.jrsperos.com

    10 Meter Fountain
    28 Skater

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  11. #7
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    Tear it all the way down. Only way to get it clean plus you may find something hidden.

    Rock
    Team Junk

    No sparkling wiggles in here, only dump truck grinches.

    "Screamin Heathen"

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  13. #8
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    Take a good look...it might just be the head gasket. Weird for one side to be so low and the other side perfect. You might just physically clean things up and put a head gasket on it and see what the compression does. For $25, it would be worth a try. Just my $.02 but it’s your $$$. Good luck!
    1990 Shadow bass boat w/ 2.4 200 Merc. Totally resto'd boat and love it!

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  15. #9
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    Quote Originally Posted by rgsauger View Post
    Take a good look...it might just be the head gasket. Weird for one side to be so low and the other side perfect. You might just physically clean things up and put a head gasket on it and see what the compression does. For $25, it would be worth a try. Just my $.02 but itís your $$$. Good luck!
    The piston has way to much slop in it, the head gasket is burnt and toast. It kinda blew my mind trying to figure out what happened, but I'm still new to all this. I guess the ring/s broke or the head gasket came apart and chewed up the top of the head, top of the piston is fine. I do have a long video of the carnage and I will document the rebuild as well along the way. I hope to pull the engine this weekend
    Click image for larger version. 

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  16. #10
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    It may have started with a head gasket but, it likely overheated. The marks are from the ring that broke and caught the port. The ring gland is probably messed up and the piston becomes a paperweight. Once you open it up you'll likely find some cylinder damage. Tear it down and check all crank journals for water marks or pit before you order any parts.
    Jim

    www.jrsperos.com

    10 Meter Fountain
    28 Skater

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  18. #11
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    Quote Originally Posted by thesignguy View Post
    The piston has way to much slop in it, the head gasket is burnt and toast. It kinda blew my mind trying to figure out what happened, but I'm still new to all this. I guess the ring/s broke or the head gasket came apart and chewed up the top of the head, top of the piston is fine. I do have a long video of the carnage and I will document the rebuild as well along the way. I hope to pull the engine this weekend
    Click image for larger version. 

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    Well THAT just sucks!!!!! Oh well, nothing but money! lol If you end up needing a sleeve or two, James Perry in TN can hook you up. He did my 2.4 a couple years back. I have 4 chrome holes and 2 steel sleeves.

    By the way, Welcome to S&F!
    1990 Shadow bass boat w/ 2.4 200 Merc. Totally resto'd boat and love it!

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  20. #12
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    Finally got the engine pulled and PH removed. I still have to get to the crank (waiting on a buddy's impact) but I also got both heads off. Some of those head bolts are a SOB, had to soak them for a week to break them loose. Pics of the heads and pistons, anyone see any reason to stop and use it as an anchor?

    How to you get the 4 long PH studs out? Heat, vise grips and penetrating oil?

    Click image for larger version. 

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  21. #13
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    PB Blaster and map gas. Aluminum responds well to heat. Map gas in blue bottle is hotter then yellow bottle.
    Its a tough engine. If there are no pits in crank surfaces you'll have something to work with.
    Jim

    www.jrsperos.com

    10 Meter Fountain
    28 Skater

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  23. #14
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    You are double nutting the studs and not using vice grips, right? Right???! Just checking...
    1990 Shadow bass boat w/ 2.4 200 Merc. Totally resto'd boat and love it!

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  25. #15
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    Snap On, and I would think other tool makers, has a device for removing studs. One of my favorite tools.

    Rock
    Team Junk

    No sparkling wiggles in here, only dump truck grinches.

    "Screamin Heathen"

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