90 hp Johnson Bogs Down with WOT

[Hoppy0704]

I have a 1983 Johnson 90hp that starts and runs fine all day long at 3000 RPM or less. As soon as I push the throttle to wide open it will run about 5 - 10 seconds then just shut down. Pulling the throttle back it will run fine again. From idle it will jump "out of the hole" like a bullet, then, after hitting 40mph, just just down.
I've cleaned the filter,and replaced all of the fuel lines, and switched tanks. The fuel pump is clean. Replaced the plugs. Help!

 

[fireman57]

Sounds like you might have some crud in the high speed jets. Remove and clean the carbs. don't just spray stuff in them remove the jets and clean them.

 

[emdsapmgr]

Possible the fuel pump is weak. The engine is consuming more fuel than the fuel pump and provide.

 

[gm280]

Possible the fuel pump is weak. The engine is consuming more fuel than the fuel pump and provide.

I second the fuel pump as well. It may be pumping enough for 3000 RPMs but when asked to supply more fuel, it can't. Time to either rebuild or replace the fuel pump in my opinion... JMHO!

 

[fireman57]

If you want to test the fuel pump have someone squeeze it repeatedly when it cuts out and see if it picks up. If it does just replace it.

 

[Rapio]

Had similar problem with 1980 - 85 HP Evinrude. Suggest you check easy stuff first. My squeeze bulb check valve was not holding pressure. Just enough pressure loss to starve carbs at full throttle.

 

[Hoppy0704]

One thing I did do when operating at full throttle was to repeatedly squeeze the bulb to force fuel through the pump. Still bogged down after a few seconds. I think I'll try a new tank/line.

 

[fireman57]

It's not your fuel pump then.

 

[Hoppy0704]

If the high speed jets were clogged....why would it run up to 3600 RPM (near 40 mph) for 10 seconds, then stall?

 

[1983 ercoa 21']

You can never go wrong cleaning the carbs really well .

 

[interalian]

I recently fixed the same problem with my '82 90 'rude. Same symptoms.

The problem with mine was a perished fuel pump output hose. It's a short hose with a tight 'L' bend, and the hose was cracked. Have a good look at the condition of all the fuel hoses. 32 years is a long time for rubber lines.