Evinrude Engine will only go half speed at full throttle- What could it be?

[Paulrd27]

Hello, I have an 87 evinrude 48hp that is having a bit of trouble. When I first took it out 3 months ago it was running fine. Since then I changed the fuel (89 octane at 50:1), Fuel filter, fuel pump and spark plugs. I also tinkered with the top screw on top of each carb. The screw is very small, does that have to be in tight? It almost seemed like it was getting too much fuel or one of the cylinders wasn't firing but I have no idea. Where should I start looking first? Any input would be greatly appreciated.

Also, I am looking to get a new prop and it looks like there's a bunch of different sizes that would fit the engine. What's a good size? It's a Bass boat so I'd like some performance. Thanks!

 

[Chris1956]

Re: Evinrude Engine will only go half speed at full throttle- What could it be?

Paul, Sounds like you need to test spark on all cylinders and take a compression test as well. What do the spark plugs look like? Do they look the same? There is an orafice on the top face of the carb. That should be snug.

 

[Paulrd27]

Re: Evinrude Engine will only go half speed at full throttle- What could it be?

Plugs are the same. I feel like when it was running good a couple months ago, the ball on the fuel line felt half to three quarters full. I was able to give it a good squeeze. Now the ball is really hard and full. Could it be it's getting too much gas?