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Tan
Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 11075
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a 98 that when taking off you have to ease into the

Customer Question

I have a 98 johnson that when taking off you have to ease into the throttle or it will choke out and has lost speed at wide open. You can also tell it is low on power at take off.
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello. My name is Tan.

Do you have spark on all cylinder in gear? Have you done a compression test?

Could I get the engine model number please?

Customer: replied 1 year ago.
I am getting spark on all cylinders and will do a compression test right now. The model number is ***** a fuel injected motor but mine is carberated is the a place on the power head that has a model number?
Expert:  Tan replied 1 year ago.

Did you check spark with engine in gear?

If this is a replacement power head no.

Customer: replied 1 year ago.
I did not check the spark with the engine in gear I will. The compressor is 95 on all cylinders
Expert:  Tan replied 1 year ago.

Ok compression is good. There is a shift switch # ***** that can kill spark on one bank of cylinders when shifted in gear. If switch is sticking or shift is a little stiff. The switch can be unplugged # ***** and test when shifted in gear again. http://www.marineengine.com/parts/evinrude-johnson-parts-diagrams/JOHNSON/52759.gif

Customer: replied 1 year ago.
I checked spark while engine was in gear and all had spark
Customer: replied 1 year ago.
I did find the the shift switch is just hanging beside the motor. Should it be mounted in place somewhere?
Expert:  Tan replied 1 year ago.

Ok that leaves fuel as the issue. When you are running the boat getting up on plane choke the engine. Does it run better? If no change squeeze the primer bulb. Does it run better? Run the engine on an auxiliary fuel source. Does engine run better?

Do you have a timing light to check timing and spark when engine is acting up? If yes connect the timing light to each cylinder when engine is acting up. Watch the flash of the light it should be steady on all cylinders.

Post back with findings and questions.

Customer: replied 1 year ago.
Did you get my message about the shift switch not being mounted in place
Expert:  Tan replied 1 year ago.

The shift switch should be in the shift bracket # ***** held in with the snap bracket # ***** spring # ***** and slider # ***** http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1998&hp=150&model=E150ELECD&manufacturer=Evinrude&section=Cylinder+%26amp%3B+Crankcase

Customer: replied 1 year ago.
Okay I see where it needs to be. Does it have to be flipped in a certain direction when put on and could it being out of place be my problem
Expert:  Tan replied 1 year ago.

It needs to install exactly as in the diagram. No this won't be the problem since you have spark.

Customer: replied 1 year ago.
Okay I will take the boat out and try what you have instructed and get back to you.
Expert:  Tan replied 1 year ago.

Ok.

Customer: replied 1 year ago.
Took it out today and tried what you said. Pumping the ball didn't seem to help any and choking it made it worse. Noticed a small leak at the vapor pump when cranking the motor over
Expert:  Tan replied 1 year ago.

Ok that ios a potential place for air to get in the fuel system. Fix that leak and run the boat again. Any kind of leak will introduce air into the system. This will cause a lean fuel condition and loss of power.

Customer: replied 1 year ago.
Will do. Is the vapor pump rebuildable or need replaced
Expert:  Tan replied 1 year ago.

That depends on what is leaking. There is one part the diaphram it can be replaced other wise the pump has to be replaced.

Here is a link to the fuel system # ***** & 38 are the vapor pump parts. http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1998&hp=150&model=E150ELECD&manufacturer=Evinrude&section=Fuel+Bracket+%26amp%3B+Components

Customer: replied 1 year ago.
Okay so I replaced the vapor pump and still having the same problem on take off.
Expert:  Tan replied 1 year ago.

When you went through the carburetors did you make sure the brass tubes in the carb body were clear?

Customer: replied 1 year ago.
Yeah the tubes that pick up fuel from the bowls
Expert:  Tan replied 1 year ago.

Yes. Are the side cover plates flat and the gasket not squished out where air can be sucked in under throttle up?

Expert:  Tan replied 1 year ago.

The plate with the 5 screws.If the screws are over torqued the engine will suck air instead of fuel.http://i.ebayimg.com/00/s/NjM0WDYyOQ==/z/1AAAAOSwHaBWi-jC/$_35.JPG

Customer: replied 1 year ago.
Do you know what they torque at.
Expert:  Tan replied 1 year ago.

Just snug the screws up till you see the gasket starting to move. This is how they told us to do them in Evinrude school.

Customer: replied 1 year ago.
Okay I may have them a little tight I will check
Expert:  Tan replied 1 year ago.

Ok I would remove each plate an inspect for warping. These plates must be absolutely flat. If bent or warped they will suck air causing poor performance.

Customer: replied 1 year ago.
Okay I ordered new gaskets and replaced them all tightening them as you said. All plates were flat. Boat still running the same
Expert:  Tan replied 1 year ago.

Hmm. I don't know what else to check. I will opt out maybe some else has an idea.

Customer: replied 1 year ago.
Could this be a fuel/air mixture problem or it not having a proper link and sync