2000 Mercury 90 HP FourStroke - Rough Idle, Dies at higher RPMs (Carbs Cleaned)

[BrodyDog757]

I have done just about everything and cannot figure this thing out. Any help would be greatly appreciated.

I have a 2000 Mercury ELPT 90 HP FourStroke (carbs) that I cannot get running correctly. The motor starts right up, however, it idles a little rough but will stay running. The more I advance the throttle, the worse it runs until it eventually bogs down and dies. I have done the following to try to get it running:

-Rebuilt and cleaned the carbs (twice).
-Replaced all fuel lines, filters, primer bulb.
-Cleaned and inspected fuel pumps for leaks.
-Tried running on external tank with fresh ethanol free gas.
-Replaced spark plugs and coils.
-Checked for air leaks in fuel lines
-New battery

The compression is 165, 175, 180, 155 (could this cause my problems?)

I was also thinking maybe it could be a bad Throttle Control Sensor, Check Valve, Dashpot(accelerator pump). Could any of these cause the boat to behave this way?

I will say that I have not properly synced the carbs, however, I figured if this was the issue it would at least run at full throttle?

I would love to have some other, more experienced, opinions on this? This is my first time working on an outboard but I am usually pretty good with motors, this is proving to be a different animal. Any ideas what I can try?

Thanks

 

[wn6ngp]

If you rebuilt the fuel pump make sure that you put all the diaphrams & gaskets back in the proper order. I rebuilt mine and I got one switched with another and as a result it would start at home and seemed to be ok but when I put it in water it would not run properly. So I went back to the book and studied the pix and realized I got 2 swapped. It wasn't easy, there are so many variations on that fuel pump. I had to carefully sort them out and compare. Lesson learned I should have been more careful when I took it apart and taken photos with the pieces all layed out. I made the job pretty hard. Yours might be totally different, I did not realize that there was a 4 stroke 90hp motor in 2000. Other thing to do to get more help here is to post the s/n the motors vary a lot. Not for me but there are some real gurus on this forum.