90 hp runs but dies at full speed

[leenihon]

I have a 90 hp engine. I can get up to speed but it will run for 5 to 10 minutes then it will die. If i hand pump up fuel line before it dies it will run for 5 to 10 minutes again. I was thinking fuel pump. I have replaced impeller so should not be overheating.

 

[Rogue I]

What type of tank? Is tank vent open? If tank vent is closed or clogged it will starve the motor of fuel.

Are all fuel connections tight? Did you recently change the water separator filter and not fill it with fuel first? Will cause engine to suck air.

Does hitting the primer / 'choke' solve the issue when the motor begins to bog? If so, you need to rebuild your carbs.

Lastly, sometimes the primer bulbs themselves go bad -- how old / what brand is it?

 

[interalian]

Fuel pump or air leaks in the lines or connectors.

 

[emdsapmgr]

Good call on the fuel pump. You did not mention the year. Hopefully it's not the expensive VRO type. If so, you might decide to convert it to the old-style mechanical (pre-mix) pump-much cheaper.

 

[leenihon]

Sorry it is a Johnson and yes the fuel pump is not the expensive VRO. Don?t know the year sorry. I have the model number is the year in that somewhere? J90TSLECM. I have changed the tanks and fuel line when problem first started thinking it would be a hose line or tank problem.

 

[leenihon]

The choke or primer does not help the engine continue to run. Only thing that works is my wife or kids on the hand pump bulb

 

[Crosbyman]

so hand pump works....I would recheck the fuel pump because it was invented to replace wife and kids pumping gas . Follow the fuel.

did you check & clean the fuel pump filter screen

choking did not help so the carb or carbs must be running empty ...

did you service the carbs (sticky needles ?)

did you check/service the fuel pump ?

 

[leenihon]

cleaned carbs with cleaner going to take back out this week. It ran better with new fuel pump but still could not stay at high rpm long enough to pull water skier. It began to run ?flooded? after 10 minutes. Took cover off and it ran much better that is why I have cleaned carbs but like said not taken it back out after doing it this weekend.

 

[interalian]

Did you tear the carbs down, spray cleaner through all the passages and blow them out? Did you pull the jets?

If any of the fuel lines in the powerhead are secured with zip ties, especially between the disconnect and pump, replace with proper fuel line clamps.

 

[racerone]

If pushing in the key to activate the primer does nothing it indicates that there is no pressure from the fuel pump.---That needs to be checked.------Posting of compression numbers may be a clue.