Motor problems

[duck77777]

I have a 1999 150 mercury that is running bad. From using my expert mecanical skills LOL I have figured out that two of the cylinders are dropping out anyone know what would make it do this.

[bay_slayer]

are the 2 cylinders dropping out, by lack of fuel? spark? compression?

[Gerald]

Originally Posted by duck77777

I have a 1999 150 mercury that is running bad. From using my expert mecanical skills LOL I have figured out that two of the cylinders are dropping out anyone know what would make it do this.

Need a little more information......

What exactly do you mean by "running bad" and "dropping out". How exactly did you determine that 2 cylinders are "dropping out".

[duck77777]

Originally Posted by bay_slayer

are the 2 cylinders dropping out, by lack of fuel? spark? compression?

It has fire checked the spark plugs compression is good dont know about the fuel it is fuel injected. The problem comes in and out runs bad then starts running good like it is droping 2 cylinders out

[Raymond]

Dat don't sound good Neg.

[bay_slayer]

Originally Posted by duck77777

It has fire checked the spark plugs compression is good dont know about the fuel it is fuel injected. The problem comes in and out runs bad then starts running good like it is droping 2 cylinders out

I'm not doubting your trouble shooting skills, but how do you know 2 cylinders are dropping out? The more information, the better we can help you figure this out.

[BIRD DOG]

There should be a fuel rail and you can check it for pressure.You should do a compression check first to see what your workin with.If compressions good then check all your plugs for spark.

[Gerald]

Originally Posted by duck77777

It has fire checked the spark plugs compression is good dont know about the fuel it is fuel injected. The problem comes in and out runs bad then starts running good like it is droping 2 cylinders out

This sounds like the problem is most likely plugged fuel injectors. Maybe try some kind of fuel addative. I think (?) I have seen a product called "Seafoam" recommended. I looked at Walmart a few months ago....and they had it..... $ 10 for a bottle.

But it could be an electrical problem.

[Montauk17]

Is it a EFI or Carb?

[Ray]

On the old carb. motors, it could be the trigger or one of the power packs.
If it is the trigger, it will be the opposite sides that are not firing. Example, #1 and #4 or #2 and #5 or #3 and #6.
If it is the power pack, it can be any of them on the same side.
Those are issues that I had with my old Mercury.

Lots of good info. on outboards on the link below.

http://www.themarinedoctor.com/cgi-bin/YaBB.pl?board=MM