25hp Johnson won't run at at full throttle

Originally Posted By: haleycat
Problem: My 2006 5 HP Mercury Outboard started easily and idled perfectly first trip this year. Wouldn't rev to full power. Assumed Ethanol affected carb or small amout of gas left from previous year. Cleaned carb and replaced, same problem. Installed new carb, same problem. Replaced exterior tank, tank line w/bulb, filter and all interior gas lines. SAME PROBLEM. Any ideas before I have to put in shop for $$$ and 2-3 month wait? I'm not a mechanic, just a parts changer with 2 left thumbs. HELP!


Half of all fuel system problems are ignition problems. And the reverse is true. Change the spark plug first.
 
New Plug but I am waiting on the local shop as I thought weak fire might be part, if not all of the problem. Thanks. I'll let you know the results.
 
I have been working on an old jon boat for a while now. Had it on the water for the first time today. It will idle fine, but at full throttle it is only running about 30% of the rpm it should (guessing). Engine runs smooth, and doesn't smoke, just will not turn up to rpm. Linkage is good and it will rev up at idle. Just no power under load. Any ideas? I'm thinking I may have a stopped up 'jet' in the carb. Its a 1975 25hp Johnson.

I don't know if you're still on here or if you still have this motor, but here is a bit of info that might help someone who reads this thread in the future.

I was perusing an outboard motor parts website and clicked on "power packs" and in the description it mentions something about RPM limiting.

Here's the link to the part I'm referring to:

It's just a thought. Maybe worth exploring.
 
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