Feels like a lost cylinder

[Lord Tywin]

89 Johnson 70 3 cylinder has been running fine, then last night at a decent cruise it dropped power. Felt like all cylinders werent firing. I throttled back and at a fast idle it was ok to limp back. I pulled the plugs, saw visible oil on a couple and swapped them out with a couple I had from earlier (used but ok). Boat ran fine back home no problem. Today I bought 3 new plugs and put them in. Boat wouldnt start, so I pulled them and made sure they were in good and the wires were seated well. Then it started fine and I took off to meet family. A couple miles in and the same problem surfaced out of nowhere. I turned around and limped back home not wanting to cut it off (in case it wouldnt restart). Back home I pulled the wires off and re-seated them. It cranked and went back to a good throttle.
I'm thinking it's the plug wires and that I can use ones like these "Sierra International 18-5231-1 Premium MagForce 9" Marine Spark Plug Wire Lead" but maybe not the 9" length as these seemed shorter.
Any other ideas of things that could be causing this? I dont have a manual so I dont know for sure these are the right ones but it looks like they are.
Any input is appreciated!

 

[oldboat1]

Did you assemble the wire connectors yourself, or factory assembled? It sounds offhand like it may be the connectors in the boots.

 

[ob]

I installed a set of Sierra plug leads on my outboard recently as I was too lazy to assemble myself a set of OEM at the time. I've had no issues with them. But yea, try and get the set that is listed for your engine and as near to the factory length as possible. Otherwise , I'll keep my fingers crossed for you that plug wires end up being the issue. I'm never that lucky...well maybe sometimes.

 

[Lord Tywin]

I pulled one of the current ones and the boots were different sizes (lengths) but the ones online seemed to be the same. I called my local marine repair and they should have me some tomorrow that are exact fit. I'm crossing my fingers too that this is the issue.

 

[Lord Tywin]

Oldboat1, these were the ones on the boat when I purchased it and they appear to be factory.

 

[oldboat1]

You apparently get some success just reseating the plug boots. That indicates to me the connectors inside the boots are not always making good contact with the plugs, or the connectors are not making solid contact with the wires. You may simply not be putting the boots on far enough -- spring coil needs to clamp to the plug. I would look into the boot(s) with a flashlight, and insert a phillips screwdriver in the spring coil -- make sure it's aligned properly. Also doesn't hurt to clean up an old connector that way.

 

[Lord Tywin]

I put the wires on my meter and found that one of them was flaky, so I ordered a new one. Put it on and took off! Purred like a well fed kitten. Until it didnt. It did it again. I had spoken with a mechanic and he thought it could also be a piece of trash in a carb that got sucked up after a few minutes.
So tonight I tested that. I ran it til it started acting up and then shut it down. Waited 1-2 minutes and it cranked up and ran fine. then it did it again. So I turned it off and waited 1-2 minutes again and it ran fine. I'm starting to think the "trash in carb" theory has validity, as after I stop the trash settles.
Now to the question...
Is there any way to get that out of the carb without pulling them off and rebuilding them? I already have the rebuild kits but wanted to wait til after the season was over to do it.

 

[Bosunsmate]

It could also be a coil failing as it heats up but as for the trash most carbs have a drain hole screw

 

[oldboat1]

Tell us how you assembled the wires/plugs.

If entertaining contamination in the carb, consider the fuel tank and fuel. Water in the fuel, possibly -- would take a sample from the tank bottom and let it settle in a glass jar. Fuel will float on top of any water.

If suspect something in the carb(s), need removal, disassembly and cleaning.

 

[Lord Tywin]

I did not assemble the wires. The ones on the boat were there when I bought it and the one I purchased was an assembled Sierra.
I had the same thought about the coil failing and was wondering how I could test that without just buying a new one?
I did a cursory inspection of the carbs yesterday to see if there was a drain plug or anything that I could find to drain the bowl but will check again.
I guess I could wait til it happens again and pull one plug at a time til I find the cylinder it's happening on then try to drain that carb?

 

[Bosunsmate]

yep try that, you can also look at the plug colous, one might look sooted up/more fouled than the others