1990 Omc Cobra 4.3 not firing on #1 & #3

[fishinghuntingfool]

I have a issue on my boat let me start. Last year I started my boat in the river and the grass clogged up the water inlet and burnt up the water impeller and overheated the motor so took the outdrive off and cleaned all the rubber pieces out and replaced the water impeller and took the boat back out and it didn't seem to run right it had a mis too it. So I parked the boat for the winter and just now started it back up for the summer and same problem with missing. I did some troubleshooting and found that #1 &#3 cyclinders on the port side are not firing. I swapped plug wires, took the manifold off and removed the valve cover and everything looks and functions fine. I took both spark plugs out and left them in the wire and both are getting spark when turning the motor over but it don't seem like the cyclinders are not getting any fuel. I'm going to get new points and cap tomorrow to see if that helps.

If anybody has any clue or suggestions I can try please let me know.

 

[Bondo]

Re: 1990 Omc Cobra 4.3 not firing on #1 & #3

Ayuh,.... Welcome Aboard,... I'd start with a Compression test...

 

[fishinghuntingfool]

Re: 1990 Omc Cobra 4.3 not firing on #1 & #3

I checked the compression just with a finger test and it seems to have good compression on both. I will check it with a gauge tonight and compare it to the other cyclinders. Thanks for your response.

 

[fishinghuntingfool]

Re: 1990 Omc Cobra 4.3 not firing on #1 & #3

So just to give you an update on the motor. I changed out the cap and points no help. Checked the compression and found that #1 & #3 cylinders only had like 15-25 psi so found the problem. So my question is what do you think the cheapest and easiest fix would be? New head or new motor? And is a 4.3 car motor the same as a marine engine? I know I would use the exterior parts off the existing and put on to the new motor. I just need some suggestions from you guys..

 

[617bsman]

Re: 1990 Omc Cobra 4.3 not firing on #1 & #3

So just to give you an update on the motor. I changed out the cap and points no help. Checked the compression and found that #1 & #3 cylinders only had like 15-25 psi so found the problem. So my question is what do you think the cheapest and easiest fix would be? New head or new motor? And is a 4.3 car motor the same as a marine engine? I know I would use the exterior parts off the existing and put on to the new motor. I just need some suggestions from you guys..

I would suggest removing the head and have it checked for being worped or cracked, depending on how hot it got, you may have only blown a head gasket.

 

[fishinghuntingfool]

Re: 1990 Omc Cobra 4.3 not firing on #1 & #3

Thanks for your response. I will work on pulling the head off this week and take it to a machine shop to have it checekd out and give you guys an update on what I find out.

 

[fishinghuntingfool]

Re: 1990 Omc Cobra 4.3 not firing on #1 & #3

So I pulled everything off today and pulled the head off and found it blown between the #1 and #3 cylinder, i looked at the head and it seems to be ok and not cracked should I still have the head looked at or just replace the head gasket.

Also dose anybody know the tourqe specs on the head and intake bolts??