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huskminn

I need my 3rd cylinder back!!!!

10 posts in this topic

I have a 1999, two-stroke, 3 cyl, 40 HP Merc.

Two weeks ago, the motor ran fine all day. Last Saturday, it started fine, but when I went to head out on the lake, there was a serious lack of power and the motor didn't sound right.

Stopped, pulled the plugs and they were seriously in need of changing and one of them (#3) was downright a mess. I've never seen a plug fouled that badly.

So, docked the boat, drove to Cove and got three new plugs. Put them in, fired it up...same problem. So, we decided to fish it that way and stay close to shore.

Last night, I checked for spark in all three cylinders....it's there. When I pulled the new plug from #3, it was mess and looked like it was already 5 years old. There was a little oil/gas mixture that dribbled out of the cylinder. Obviously, it wasn't firing. I cleaned everything up, put in one of the cleaner old plugs and ran the motor. It seemed like it was firing once in a while. The #3 plug was warm, but not as warm as the other two.

I pulled it out, noticed no dribbling out of the cylinder, put in another old, unfouled plug and ran the motor. It definately ran better, but the #3 plug still didn't get as warm as the other two. It was a different brand and a buddy told me that different brand plugs will run at different temperatures.

I ran out and bought three new NGK plugs, gapped them and put them in. I am hoping that the motor will run now and I'll test that tomorrow night.

I have a theory that the #3 cylinder had so much dump in it that it just immediately fouled the new plug right after it was put in.

Any thoughts on this....similar experiences??

Tell me I don't have a bigger problem.

[This message has been edited by huskminn (edited 07-02-2002).]

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The 40 Merc has been a great troller for me. Runs down to about 1.5 mph in calm conditions. I think the excessive amount of trolling that was done two weeks ago may have contributed to the fouling of the plugs (I hope!!).

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I am not a mechanic, just experienced with problem solving for goofy things that go wrong over the years.

I had a motor once that had 3 cylinders and a similiar problem. I found out that the choke was stuck (choke cable fell off carb) on the one carb that was not firing properly, and all the carbs were basically out of tune.

Pull the cover off the carb intakes and inspect to see if everything is synchronized, and, who knows, maybe the carbs are just out of tune and might need professional tools to get them back in order.

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Take the third plug out and start the motor. This will bow all the gas and oil that built up. Put a new plug in and dont put the plug wire on all the way leaveing a 1/4 in gap. Start her up and and run for a minute, Turn it off and put the plug wire on all the way.

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I'm a user, not a mechanic, so I can't help. I do, however, own a 90 hp Merc (3 cyl) which is on my fishing boat -- Frankly, the 3 cyl is a rough runner at slower speeds even after tune-up (this is '98 equipment).

I have a 40 hp Merc (2 cyl) that sits on the back of my wife's pontoon for weeks on end, fires up when needed, and runs great at any speed from slowest to wide open.

Hope you get your problem resolved more inexpensively than I did -- I ended up buying a 9.9 hp Merc four-stroke as a kicker. I simply cannot troll with the 90, even though years ago I had a Merc 115 (6 cyl) that would troll all day on Lake Michigan. My what mysteries motors can be.

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i also had a 99 40 hp merc. and was cutting out in 1 cyl. brought it back to dealer and the problem was that merc uses alot of forma-gasket when they put there motors together and in the bottom carb a peice of gasket broke off and was sucking up in the main jet causing it not to run.
one day it run great the next day it did'nt after he removed all the bowls on the carbs and removed the tiny peice of form-a-gasket it was back to running like a champ!!!!
good luck finding the problem!!!

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Hmnnn......very interesting replies. Thanks for the input.

ST, I think I have succeeded in getting most of the build-up out of the 3rd cylinder by simply running it, removing the plug, putting in a dry plug, running it again, doing the same a third time. The last time I ran it, I checked the plug and it seemed to be in fairly good shape.......I think the build-up is gone.

Unless of course, there is a problem with the carb.....whether it be a piece of gasket or it is simply out of adjustment.

I'm going to try to run it tonight and we'll see if #3 runs as it should be.....if not, it's off to the shop. I am not a mechanic and I don't even want to think about messing with the carb.

I really appreciate the input....have a great 4th and don't forget to celebrate and take note of the freedoms that we have and that we must continue to protect.

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I hope the "build up" on your spark plug isn't aluminum from the rings. That would be a failure or clog of the injection system.


Otherwise, it sounds like you have excess oil in the #3 fouling the plug. Why that would happen is hard to diagnos unitl you tear into the carbs.

PCG

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After replacing the plug a couple of times, I took the boat out on Wednesday and it ran fine.......3rd cylinder fired as it should.

I also ran it on Friday with the same results. I'll pull the plug this week to check it for build-up, but it seems that the cylinder finally cleaned itself out.

Thanks for all your help.

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You might want to try some sea foam in there!

------------------
Hunt&Fish tell you drop!

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