Need help with my outboard

[fisher]

I have a 1992 40 HP Merc outboard, 4 cylinder - 2 Stroke.

 

My boat has been smoking more than usual lately so I pulled my spark plugs and noticed that 2 of them were very dirty (the 2nd and 3rd plug from the top - they run straight top to bottom). The 1st and 4th were much cleaner. Problem is that I forgot to record which wire went with which plug (assuming they were right to begin with). Coincidently, the spark plug wires also run top to bottom (just to the right of the spark plugs).

 

I noticed on the motor written "firing order 1, 3, 2, 4".

 

Does that mean I need to re-attach the spark plug wires in that order (ie. meaning the top wire to the top plug, the 2nd wire to the 3rd plug, the 3rd wire to the 2nd plug and the 4th wire to the 4th plug)? Or do I attach the first wire to the first plug, 2nd wire to 2nd plug, 3rd to the 3rd and 4th to the 4th)? Or does it matter.

 

Sorry for the noob question..and thanks for any replies.

 

BTW, I am buying new plugs tomorrow.

[Fisherman]

Firing order should not have anything to do with the lcoation of the wires. Worst scenario if you don't get them in the right order, it won't run right and you'll have to switch them around.

[fisher]

Thanks for the reply but was hoping for a more definitive answer. I am wondering if the smoke that I have been seeing was because they were not in the right place before I took them out And that may explain why the 2 middle plugs were dirtier than the others.

 

Any marine mechanics out there?

 

Thanks again.

[SBCregal]

edit... too early, coffee hasnt kicked in yet.

Edited August 12, 2010 by Dunner

[fisher]

edit... too early, coffee hasnt kicked in yet.

 

 

too bad, got my hopes up

[Fisherman]

If the wires were not connected in correct sequence, it would be running like a bag of hammers, you would definitely notice the difference. If it's a multiple carb unit, they may need a thorough cleaning and rebalancing. Give it a healty dose of Seafoam and take it for a good run, it will smoke like a friehgt train and burn the carbon out. Next, get yourself some synthetic 2 stroke oil, doesn't foul anywhere as bad as dino oil. And lastly, it's still a 2 stroke and they tend to foul plugs if everything is not adjusted to optimum performance, just the nature of the beast.

[Billy Bob]

Firing order is VERY important and you must get the correct wires in their proper order.

 

Since no one has the proper order (so far) including myself I would suggest a call to a local Merc dealer and I'm sure they will be happy to answer that FREE of charge.

 

There are many reasons why a motor fouls plugs so guessing is not the answer either. New proper plugs with the correct gap settings are in order I would say, and then the correct wires to each. After that has been done I would monitor the situation by pulling the plugs after each outing. And I would keep a record of how the outboard was used...ex..trolling or all high speed running. Then if the plugs are fouling badly I would try to find out why as this is not the norm.

 

BTW I was really surprised to see that a 40 HP Merc has 4 cylinders...my 1985 50 hp Johnson only has 2 cylinders and never fouls the plugs even with many hours of trolling. However, it's a VRO (oil injected) motor.

 

Good Luck,

Bob

[SBCregal]

with the cylinders being right next to each other ie. cyls 2 and 3, you may have a head gasket problem, or cracked block between the two cylinders. it could cause a loss of compression in both cylinders and cause misfiring and fouling of the plugs. go to princess auto, walmart or canadian tire and pick yourself up a compression tester, google for directions if you cant figure it out...its really quite easy. not sure what exactly the spec on your motor would be, but if the cylinders arent within 10% or so of each other, its not good.

 

ryan.

[aplumma]

A compression test is the first test to see what the health of the motor is. A spark test is the second test to verify the coils can light the mixture and the plugs are working. After that it is just a matter of detective work to see what part of the combustion triangle is lacking for a complete burn on the two cylinders A.I. oxygen-fuel-heat. Big Cliff has in the past donated a lot of information on small engine repair and Bernie has as well both of them will have the correct answer without guessing.

Finally here is a caution for incorrect advise Their is a stopping point you can easily cross for home mechanics who can inadvertently destroy a motor just by turning a screw the wrong direction. I have had motors come across my bench that someone turned the high speed jet in because it made it faster and toasted the block on a motor that could have run for many more years. How to fix something you don't understand and medical advise are the two worst things to ask on an internet forum.

 

 

Art

[Pikeslayer]

I would certainly promote Art's advice. Ask around the marina or wherever you launch for referrals to a reputable trained and certified Merc mechanic (they will have current 'certificates' posted @ the service desk). There is probably a lot of life left in in your Merc and it would be shame to shorten it.

BTW, I have a '91 Merc 115 which is a 2 + 2 cylinder. It only runs on 2 cylinders when @ trolling speeds. These plugs get cleaned/replaced more often than the other 2. I'm not sure if the 40 was manufactured with the same option.

I hope it is just a minor issue for you

 

Regards,

Symon

 

p.s. I learned a couple of expensive lessons by not following advise similiar to Art's. I am located in Ontario, so unfortunately I couldn't refer anybody in your area. But you could look on Mercs website to find authorized dealers.