1979 70hp Evinrude

[dallie]

Help! I have recently rebuilt the carbs and had a test cruise. Ran well but lost prime so I changed out fuel line and ran great for the next outing. then began having trouble with power loss at acceleration. Sounded like it was bogging down, flooding out etc. Now will not go past a slow idle. On the muffs it idles great but hesitates when manually throttling to higher rpms. Installed fuel filter and changed to new gas and still the same thing. ODD as it seems, in the water I can remove the cover and I get a little more power. Also the same is true when I tilt the motor up. Could the carb floats be sticking? Fuel pump bad?

 

[oldrudedude]

Re: 1979 70hp Evinrude

I think some little piece/pieces of crud from the old fuel lines have lodged in the carb jet/jets. When you say "lost prime" not sure what you mean because as soon as the engine starts the primer bulb becomes soft as the fuel pump starts to suck gas from the tank. Which fuel lines did you change?

 

[dallie]

Re: 1979 70hp Evinrude

Thanks for the reply. I lost prime on the primer bulb from the 6 gallon portable fuel tank. I changed the fuel line from the tank to the motor but none of the lines from pump to carbs. Maybe it is a good idea to change all of them. I will remove the carbs again and clean them whil replacing all lines and hopefully that will help.
Still perplexed over the power gain when motor cover is off while in the water.
Thanks again.

 

[Daviet]

Re: 1979 70hp Evinrude

Did your engine quit or did the primer bulb just go soft?
Usually if the engine runs better with the cowel off it indicates a leaking base gasket allowing exhaust to collect in the cowel starving the engine for air.

 

[dallie]

Re: 1979 70hp Evinrude

The engine was still running and the primer bulb went soft. If it is the gasket how difficult is that to replace and does that indicate other more serious problems? Also, by tilting the engine up while running it gains a little more power, could that be tied to the base gasket too?

 

[Daviet]

Re: 1979 70hp Evinrude

The primer bulb will not be firm once the engine is running, it gets soft.
You have to remove the power head to replace the gasket, but there are more checks that you can do to confirm a blown base gasket.
When you tilt the engine a little, are you sure you are not actually trimming the boat and getting better preformance. How much are you tilting it up?

 

[dallie]

Re: 1979 70hp Evinrude

While going full throttle I am still getting only a little over idle speed except when I tilt the motor about 1/3 up. Even at that I still do not get enough power to plane out. Another thing is that when it did run good after the carb rebuild it had a muffled sound when running at higher speeds, could this be due to the gasket?

 

[Daviet]

Re: 1979 70hp Evinrude

A blown base gasket will have no affect on the engine with the cowl off. By tilting the engine the only thing that could move is the floats in the carbs. Did you set the float level when you overhauled the carbs?
Have you checked the compression and spark?

 

[dallie]

Re: 1979 70hp Evinrude

Thanks I think you have hit on something. I was not sure the floats were working properly and that is what I thought the tilting of the motor may be affecting to give me a little more power. I did not set the loat level. I think it requires a special tool that I do not have. Is there any way to set it without that tool? No Compression check but the spark is strong and blue. I think I need to take the carbs off again and check the floats. What do you think?

 

[Daviet]

Re: 1979 70hp Evinrude

You don't need a special tool to set the floats, take a look at this, it might help you out.
http://forums.iboats.com/showthread.php?t=244013