1987 1.6L OMC seadrive misfires I can't tell

Joined
May 31, 2007
Messages
7
Well I have a 1987 OMC 1.6L seadrive that has not been ran in about 3 years. The last time it ran it ran well and no issues. Now after I did a lot of work on it, the motor seems to have a random misfire.This is all that I done so far and done in steps.
  • removed all fuel from tank and looked inside of tank and it is clean and the fuel is good
  • replaced fuel water filter seperator
  • replaced fuel bulb and checked all connections
  • flushed all fuel lines

Then once I got the fuel situation squared away I put a fresh fuel in the tank and tried to fire it it up. It ran but it had a persistant misfire It would run with the ears on but when I put it in the water and it had the backpressure on the exhaust it would not stay running. So then I replaced or repaired these components.
  • removed both carbs and rebuit them
  • replaced all coils
  • replaced all spark plugs
  • replaced all spark plug wires

So I fired it up and now it doesn't have a persistant misfire but now when I have it running on the hose with the ears it sounds like it runs good but the motor seems to have a random miss. When this happens it is like a single misfire and it would cough out smoke like when it has the choke pressed for a second.

So I have some questions if anyone wants to field them. Also the motor seems good mechanically. The compression is good, got fuel and spark.

  • Does this run like this normally out of the water because it has no backpressure on the exhaust and the issue will go away when in water?
  • Could it be that the choke is activating on its own and dumping fuel like the choke is depressed?
  • Could this be a engine synchronzation issue?
  • Is it because the idle is to high out of the water?
  • Would it act this way if the idle is to high because it may need to be adjusted to be little lower?
What is the best way to test for spark at each cylinder while the engine is running?
I have used some different things so far and none seem to work to well. I don't want to spent a boat load of money on the testers they say to use in the manual. I want to see if a cylinder is breaking down but it is random times it happens and I am not sure if it a spark issue or a fuel issue. I would like to look at spark at each cylinder and try to isolate it to rule out a spark issue. I may have missed some minor details but I will add them if I can think of them. Not real good at all of this typing. Any help would be appreciated. All I want to do is go out on the boat and have some fun.
 
Joined
May 31, 2007
Messages
7
Re: 1987 1.6L OMC seadrive misfires I can't tell

Just checking in to see if anyone out there has any ideas. Looking for some help. Thanks.
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: 1987 1.6L OMC seadrive misfires I can't tell

Get an inductive timing lite and when it's running hook it up to each plug wire and look into it. When you see black spots that's the cyl that's miss firing.
 
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