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Thread: Outboard motor question

  1. #1
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    Default Outboard motor question


    Hi everyone. I have a 1998 Force by Mercury, 75hp. Now I'm not a super mechanical type of guy, but I do keep the lower unit oil changed, keep good plugs in it, use stabil when it's down for a while, all that. So here's my question.

    On the back of the outboard, just below where the cover is, on the thin part of the motor, there is a hole. I'm not sure if it's an exhaust outlet or what, but I'm sure you all know the hole I'm talking about. Well here's what's happening. After a day on the lake, I notice that a thick oily sludge is dripping out of this hole. It's more noticeable in the winter because it's thicker, and stays on there. In the summer much of it washes away. But in cold weather, it's a thick little line of what looks like oil sludge coming down out of that hole.

    Is this normal? Or is this something I need to be concerned about? The motor runs fine. Very responsive and idles OK. It's always been a little tricky to start, but other than that it runs fine.

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    Sounds like you are talking about the exhaust. This is normal on older engines. Might be a little rich, but if it is running fine and not fouling plugs I would not worry about it.

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    OK, that makes sense. It probably is running rich, it's a dog to start sometimes, and I have not had anything done to the carbs in the 8 years that I've owned it.

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    Run some Sea Foam in it and see if it helps. The carbs are very basic. Just get a shop manual and rebuild them if need be. I would have the kits and carb cleaner in hand before teardown. Might want to do the fuel pump while you are at it.

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    sounds like it could be oil you've spilled over the years pooling and finally building up enough to seep out. motor running fine? look for something simple

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    Thanks guys. At least I know it's not some major problem that would keep me off the water. Just sounds like maintenance type things. Thanks for the tips.

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    Does this hole have anything connected to it inside? Any hoses? Or is it just through the housing?

    Most outboard motors exhaust under water. The water is used as a muffler. Ever fire her up outside of the water? Loud as heck. Anyway, it sounds to me like you are describing what some call, "the pee hole". This is a hole that allows the water brought in by the impeller to exit the motor after it's ran through it cooling the motor. If you are getting oil sludge in it, I suggest you take your motor to a qualified marine mechanic before you take it out again. You may have blown a gasket in your head area somewhere allowing water and oil to mix, which is never good. I hope I am wrong, but an ounce of prevention.....
    Last edited by Crappie Reaper; 01-01-2009 at 11:02 AM.
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    You might, also, post your situation here iboats Boating Forums

    Lots of good advise there...
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  9. #9
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    A picture would help some but I believe you are talking about the exhaust relief ports...most outboards will have one or two on the midsection of the engine...there will be water kind of spitting out of this at idle on most when they are warmed up and "in water" some won't do it on muffs...the pee hole as described earlier should have a nice steady stream of water coming out of it....weather on muffs or in the water. It just tells you that your water pump is working...it normally exits out at an angle so you can see it...some will exit straight out the back but most at an angle so you can see them when your in the boat. The main exhaust exits out under the water as said before so they are not loud on the water. I really think you are talking about the exhaust relief ports though...if you put your hand over it or them if there are two you will feel some exhaust coming out...not a whole lot but some...they are there to releive some of the pressure....you'll see smoke coming out of them from time to time also...ecspecially on a cold start up.

    Sounds to me like you have carbon build up in the engine. We have to remember that our two stroke out boards are some of the hardest working engines out there...how many gears do you go through to get to your top end?? none...it has to go from a standstill to full speed with one gear. Thats why propping is so important on outboards...if you are overpropped by even a little to put you at the lower end or below the recommended rpm range you are lugging the engine...not only at low rpm but also at wot. Think of it as an old car or truck that gets lugged around by someone...every now and again it was always good to go out and blow the soot out of an older engine...that soot was carbon build up. On a two stroke our oil is either mixed by hand or by mechanical means...VRO..etc...When we ease around alot, overmix our oil a little bit, or our oil injection sends a little more oil than we need that oil that doesn't get burnt either comes out as smoke or it builds up...eventually coming out as sludge as you described. This sluge can be a bad thing as it gets on the rings and causes a situation we call coking....thats carbon build up on the rings...if this carbon gets hard the rings eventually will "stick" and even break off. Then poof goes the engine.

    All this being said, thats why your BRP xd100 and I believe x50 and your Merc Premium plus have additives in them such as "ring free" or "seafoam" those are not whats in there as each manufacturer will put their own additives in there oil...this help keep coking from happening. If you are running a regular two stroke oil...xd25 xd30 merc premium or penzzoil or any of these they do not have an additive in them to prevent coking. This is where products like seafoam, ringfree, and others you'll see at walmart or your marine store ie...bass pro, gander mountain, etc... come in. If your outboard is dripping sludge you need to do a "decarb" and soon. There are COUNTLESS ways to do this...I use seafoam...I actually run 3/4 can in 12gal about every 3rd tank in my old ranger. Then once a year I take a 3gal gas cantainer, put one gallon of gas in it, put 3/4 can of seafoam in it...if you premix your oil put the recommended amount probably 50:1 in it...if you have oil injection you'll have to see how its hooked up first...if anything you can just run the fuel line from the fuel tank and hook it to your 3gal container. Put the remainder in a spray bottle....go to the lake and run for about 10 five or ten minutes...stop and fish or just sit around for 15 mins...start up and do that again...repeat this until you run out of gas....hook your gas tank back up...pull cowling off and spray the rest of the seafoam in the carbs while the engine is running...when you are done with that put cowling back on and let her rip. You can also do this in your driveway on muffs, just do not rev it up...never rev an outboard on muffs as they can run away without any pressure on them. If you go to the lake or something to do it take a spare set of plugs with you...you'll need to replace them when your done. After you do this run seafoam or an additive like it every few tanks and you will not have any carbon buildup or sludge anymore. Just to let you know when you do this, you'll see ALOT of black stuff from the exhaust and exhaust relief ports...this is the carbon build up coming out. If its real bad you can also spray seafoam in each cylinder and let it set over night. Hope this was clearer than mud and sorry for it being so long...pm me if you have a question or anything. Most shops can do a decarb also. I just really think if you have sludge coming out of it you need to decarb soon...as there is no telling how much buildup there is. If you go to iboats.com and look up decarb you will see more information about it. There was a post a while back about seafoam and I posted some links to a GREAT write up about decarbing and the hows and whys of it if you can find it.
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  10. #10
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    Scrapper put out some good info. If your motor runs higher or lower than the recommended RPMs at WOT, its lugging. Unfortunately the only way you can tell this is with a tach. Here is the instructions for doing a de-carb and like the instructions say Don't do it on a nice clean driveway. Decarbing Your Engine- The Process-HOW AND WHY - iboats Boating Forums
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