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  1. #1
    Petty Officer 3rd Class
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    Default How to find/evaluate a good used 4 stroke?

    I would like to find a good bargain on a used 50-70 hp outboard, but I'm a bit baffled on how one goes about evaluating one. If you're not an outboard mechanic, aren't you just tossing the dice as to the mechanical soundness of a particular engine? Seems like every engine seller on Craigslist advertises "low hours" etc etc.

    I suppose one could go to a reputable dealer which might get you a good engine, but you will pay the premium price. If you go to a private owner, it would seem that you would have to insist (and pay for) a full check by a qualified mechanic.

    I'm wondering how others handle it. Any thoughts appreciated. Thanks.

  2. #2
    Lieutenant Commander
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    Default Re: How to find/evaluate a good used 4 stroke?

    Best bet is to buy an engine that's mounted on a boat so you can run it in the water. Then you and the owner agree on a price and agree to have the engine inspected by a qualified marine mechanic.

    If it's okay, have a mechanic use a scanner to check out the motor. The later model motors can tell a scanner the exact hours it's been run and how many hours it's been run in rpm ranges, like 1000-2000, 2000-3000, 3000-4000 and so on. If the engine has put out any trouble codes, the scanner will tell. You'll then know how it's been run it's whole life.

    If everything checks out, your qualified mechanic should drain the lower unit lube--looking for signs of water contamination in the lube. If okay, he'd do a pressure and vacuum test on the lower unit to check if the seals are good. ($300 repair if bad.)

    Then you pay and take delivery.

  3. #3
    Petty Officer 3rd Class
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    Default Re: How to find/evaluate a good used 4 stroke?

    Quote Originally Posted by Bamaman1 View Post
    Best bet is to buy an engine that's mounted on a boat so you can run it in the water. Then you and the owner agree on a price and agree to have the engine inspected by a qualified marine mechanic.

    If it's okay, have a mechanic use a scanner to check out the motor. The later model motors can tell a scanner the exact hours it's been run and how many hours it's been run in rpm ranges, like 1000-2000, 2000-3000, 3000-4000 and so on. If the engine has put out any trouble codes, the scanner will tell. You'll then know how it's been run it's whole life.

    If everything checks out, your qualified mechanic should drain the lower unit lube--looking for signs of water contamination in the lube. If okay, he'd do a pressure and vacuum test on the lower unit to check if the seals are good. ($300 repair if bad.)

    Then you pay and take delivery.
    Thanks for the info. That's information I can use. Didn't know about scanners. I'll check around and find a shop that can tell me what year motors are available with that technology.

  4. #4
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: How to find/evaluate a good used 4 stroke?

    Not all motors have that option. Only those with electronic fuel injection. Carbed engines do not have that ability.
    Even with Efi, it's model specific. The scanners are different between a Merc and a Johnson for example.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

  5. #5
    Supreme Mariner Frank Acampora's Avatar
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    Default Re: How to find/evaluate a good used 4 stroke?

    There are other clues that are easy to spot: The general overall appearance, for one. If the owner did not care about how the engine looks, then he probably did not maintain it well. Obvious corrosion of external parts and bolts means a salt water used engine and possibly one to stay away from.

    A cheap compression tester (30 dollars) will tell you the general overall health of the engine itself. This only requires pulling the sparkplugs and cranking the engine with the tester hose screwed into plug holes. Equal compression on all cylinders is good. Great differences or low or no compression on one or more cylinders means an engine needing major repair work.

    The general condition of the sparkplugs will also indicate general health of the engine. Look up what 4 cycle plugs should look like after running in an engine.

    You don't need a trained mechanic for any of these tests. You just need to be able to read and interpret results.

  6. #6
    Supreme Mariner Silvertip's Avatar
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    Default Re: How to find/evaluate a good used 4 stroke?

    While there are differences between two and four stroke engines from a mechanical standpoint, you evaluate each the same way.
    1) Does it run? The verification is to have the seller prove it.
    2) Because it runs, is not an indication it runs as it should. Again -- have the seller prove it with an on water test.
    3) If he/she refuses, then adjust any offer significantly downward or insist that the owner pay for a professional evaluation. You may even split the cost if there is not reason to suspect a cover-up.
    4) On four strokes, check the engine oil on the dip stick. If it is low, milky looking, or smells burned the engine may have issues (especially with milky or burned oil).
    5) The lower unit lube check (again for water), and the other general condition checks can be done by you. Even a compression test is cheap and easy to do.
    6) Outboard engines (new and used) are getting more expensive every year so spend you money wisely. Asking questions and getting answers you want to here is NOT verification that the answer is true. You need to be the judge. Answers like "runs good -- just needs xxxxxxxxx) is a clue that something is not right. If was just xxxxxxxxx the seller would fix it.

  7. #7
    Supreme Mariner
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    Default Re: How to find/evaluate a good used 4 stroke?

    As I was helping my son look for his first car, I gave him this advice: Always assume there is something wrong with it. Then it is up to you to figure out what that something is. Then you pays your money and takes your chances.

    Ever watch Judge Judy? She always asks the plaintiff if he had a mechanic look at the car before he bought it. Of course he always answers "no". Case closed, verdict for the defendant.

    Hey, I was a professional outboard mechanic and even I can't always detect what is wrong with it. As verified by the times we got stung on trade-ins. A motor can run just fine and pass all the tests, but lo and behold the guy welded the drive shaft splines----just one example we got stung on.

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