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86 merc 75hp problems. - Page 2 - Walleye Message Central
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  #11  
Old 06-17-2019, 08:57 AM
tolson93 tolson93 is offline
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Thank you REW! Will be reporting back on what I do and how it ends up going.

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  #12  
Old 06-20-2019, 11:44 PM
tolson93 tolson93 is offline
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Ended up getting two new fuel tanks and fuel line from tanks to motor. Fresh gas and switched to a semi synthetic pennzoil.

Did the seafoam treatment and smoked the yard out. Seemed to run fine on muffs.

Have had it out two or three times now and seems to run like it used. Slight miss or hesitation that is very minor. Thinking It could be the weaker cylinder. Used about 10 gallons through it. Started acting up last night but I did some slower driving 5to 10 mph to look for fish on structure. Maybe that did not help or the fact I was getting low on gas in that tank.

Overall, I am coming to the conclusion I had some rich mixtures going through the motor. Used to mix with injex and the color of the mixed gas was very dark purple. So hoping I sorted it out.

One last question, in my situation with the old tyee and the motor that has a weaker cylinder would you look into rebuilding or re powering? I plan on hopefully getting a newer boat in less than let's say 5 years. So I'm trying to prepare for what I should do.

The boat can handle a 100hp. I don't wanna dump thousands into it. Curious on your guys opinions or what you have done in these situations.

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  #13  
Old 06-23-2019, 04:29 AM
REW REW is offline
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If you have a decent motor with one weaker cylinder, just keep some spare new spark plugs on hand.

When the weaker motor fouls a plug, remove the plug, replace it with a new one and toss the fouled plug when you get to shore and a decent garbage can.

You can likely get another 5 years out of the motor without spending a lot of money on it.

Best wishes.
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  #14  
Old 06-24-2019, 08:33 AM
staylor staylor is offline
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X2 on REW’s suggestions- keep some extra plugs around and run it until it won’t light the weak cylinder when you’re on-plane. Many years back I had a 4 cyl Merc 50 with low compression on 1 cylinder due to a leaky lower crankcase seal- I bought the motor “as is” for $100. It trolled really well on 3 cylinders and the dead cylinder would light up as soon as I gave it enough throttle to get on plane. I asked a dealer what to do since I didn’t want to start taking things apart. He told me to just leave it alone since he suspected it would not troll as well on 4 cylinders since the dead cylinder was putting a constant load on the engine which would smooth out the motor at low speeds. I didn’t believe him so I ended up dropping the lower units, pulled the lower end cap, and changed the seal. The end result was that it ran on 4 cylinders at all times, but was rougher running at trolling speeds than it did on 3 cylinders. I mentioned this to the dealer and he laughed and told me that in the dark ages of the 1930s and ‘40s when 2 and 4 cylinder motors used opposed cylinders rather than in-line it was common practice to short out the spark to 1 cylinder when trolling to make the motor troll smoothly.

As an aside, put in some new spark plugs, run it for awhile, and see how the plugs look. If they are still black and gummy, you can try going up 1-2 heat ranges in the plugs to see if the motor runs cleaner. For example, when I ran Evinrudes in the 1980s, it was common practice to go from an L-78c plug up to an L-82c to keep the plugs from fouling. Similarly, the 1950s Merc always ran better on a J7J or a J8J plug than they did on the factory J6J plugs.
Doug
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  #15  
Old 06-24-2019, 09:14 PM
tolson93 tolson93 is offline
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Sweet thanks guys! And yeah I'll have to look into those plugs and see if they help any. Never thought of that one.

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  #16  
Old 06-24-2019, 09:20 PM
tolson93 tolson93 is offline
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I'm running a ngk buhw-2 , would you know off the top of your head what plug would run hotter? I'm googling it but not having luck.

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  #17  
Old 06-25-2019, 10:52 AM
staylor staylor is offline
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Fun with spark plugs time! The NGK BUHW-2 is a surface gap plug- and these are notorious for fouling in older engines. This is also the hottest heat range available in a surface gap plug that fits your engine. So....the alternative is to go to a gapped plug.

BUHW-2 is equivalent to Champion L-78V in a surface gap

Alternative gapped plug in the same heat range is the Champion L-78C

A slightly hotter plug in a gapped style is the Champion L-82C,

The gap setting will be .04 if your ignition is in good shape, or .03 if it’s not.

Coincidentally, this is the same swap I used to do in my Evinrudes in the 1980s. I would typically run a .03 gap. On my 225 Evinrude Vindicator, a relatively high performance motor in its day but with a fairly “wimpy” powerpack, I would run the L-82C at .03 gap and also very carefully file the center electrode back(with a razor blade inserted into the gap to keep from having my file hit the center electrode) to a so-called J style, where roughly 1/3 of the center electrode was not covered by the outer electrode. This trick of exposing some of the center electrode was an additional way to reduce fouling, and was a standard feature in the 1950s when ignition systems were conventional magnetos. A typical plug back then in the Mercs was a Champion J-6J, the last J signifying the unshrouded center electrode.

My 225 ran like a top with the modified plug...until I sold the rig after 10 years to an idiot who decided it was too much work to swap between the ski prop and top end props I sold him and decided it was dumb to run 93 octane in an engine that was supposed to run premium 91+ octane. He put in 87 octane gas at the local Indian Reservation, left on the high pitch top end prop, and liked to pull 2 skiers at a time....until he put a rod thru the block! I got him a deal on a replacement powerhead.....
Doug
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  #18  
Old 06-25-2019, 01:18 PM
tolson93 tolson93 is offline
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Is there any potential issues with switching from the surface gap plug? Cause if a simple plug change could help my motor run better I'm all for it .

For the most part its been pretty good. Ran about 10 gallons through with little hesitation here and there.

Seems like if you wanna accelerate hard from a idle it seems to bog, and you have to play with the throttle to get rpms up. Overall, I'm not too worried. I figure a 1986 two stroke with one cylinder being a little weaker isn't going to run perfect or anything.

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  #19  
Old 06-25-2019, 02:33 PM
staylor staylor is offline
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I never had any issues. On the Evinrudes they let you use either plug, just a straight swap. All the plugs I listed should have identical threads and thread lengths, and your motor is not high compression so it should have plenty of clearance to handle a gapped plug. If you want to stay with surface gaps, try the L-78V Champion which I always felt ran a bit better than the NGK surface gaps.
Doug
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  #20  
Old 06-30-2019, 05:33 PM
tolson93 tolson93 is offline
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Gonna try the hotter champion plugs tonight. Here are some pics of the plugs I just took out. Starting running a little rough last time it was out , but the plugs looked dark like they have all summer. Any thoughts on the plugs? Almost all I have changed look the same.

Been sitting over a week too as I just pulled them. https://uploads.tapatalk-cdn.com/201...3f4221615f.jpg

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