2003 Mercury 125 Saltwater not reaching full rpm

[mattc8821]

have an 03 merc 125 2+2 on 20ft dual console.

boat is only getting up to about 4500rpms / 30mph. 16p prop. When checking spark on trailer, all 4 cyls have good spark. I put new plugs in and ran it for a while up and down canal . Pulled plugs and bottom cyl plug looked brand new. No color, no fuel on it. Ran it again, got up in rpms , sprayed some fuel down that carb throat and no change in speed or rpms. So confused as to whether or not it's a spark or fuel issue

Motor has over 120 psi in all 4cyls
carbs are freshly rebuilt and 100% clear
new plug wires and boots
reeds inspected and all good

 

[jcole108]

I had the same problem with my 2006 Optimax. It all cleared up when I replaced the fuel line. The new Mercury fuel line works better with the ethanol. I was able to see were the inter lining of the original fuel line was coming apart.

 

[Texasmark]

I had the same problem with my 2006 Optimax. It all cleared up when I replaced the fuel line. The new Mercury fuel line works better with the ethanol. I was able to see were the inter lining of the original fuel line was coming apart.

I had a similar problem on my 02 several years ago and I'm talking about the OEM grey, silicon looking hose with no reinforcing fibers like regular black automotive fuel lines. The crud is tan and forms to the inside of the fuel line if it hasn't broken into little pieces, probably have some of both. At a restriction is where you can easily find it.....like where the squeeze bulb is inserted into the fuel line, or where the fuel line enters the engine either by removable connector or union.

If you have a removable fuel connector at the engine, get a clear container and using a wooden dowel to depress the sealing ball in the connector, depress it and squirt some fuel into the container. If you see brown crud you are a victim.

If fuel down the carb throat didn't make any difference, any difference, then something else is wrong. "direct injection" should be result oriented and totally eliminate any fuel issues if fuel starvation was the culprit.