Motor boggs down at 3/4 to full throttle

[matagorda]

My '87 Evinrude 90 h.p. will run wide open for about 500 yards and then bogg down. I can throttle it back and after about a minute it will take off again. Sometimes I leave the throttle at full and it will lunge a couple of times and then take off after about a few minutes. I've cleaned the tank,carbs,put new primer bulb in fuel line,plugs,filter, and fuel line. PLEASE HELP!

 

[rickdb1boat]

Re: Motor boggs down at 3/4 to full throttle

matagorda <br />Did you make sure the fuel tank vent is clear or try running with the gas cap loose? Is the bulb staying firm when this occurs? And if you pump it, will it take off? How about the anti-syphon valve going into the fuel tank? Could be fuel pump.

 

[matagorda]

Re: Motor boggs down at 3/4 to full throttle

Yes, I've tried pumping bulb, but it doesn't change. I forgot to mention that after it's been idling stopped for awhile it leaves a large gas or oil film on top of the water. When it's been running forward at idle speed, it stays bogged down for a long time or until I leave it off for about 30 minutes. Thanks for the info. and I'll check the rest you suggested.

 

[rickdb1boat]

Re: Motor boggs down at 3/4 to full throttle

You might take a look at the carb throats while running to see if gas is spitting back out any of the carbs. If so, you may have a stuck open Float/Needle Valve in one of the carbs. This would require rebuilding the carbs to fix the problem. Does'nt sound like the fuel pump is bad if there is no change when you pump the bulb and it stays the same. Check out everything else first and get back to us.(Did you set the float level on the carbs when you cleaned them? And did you just clean them or rebuild them with a kit?)

 

[matagorda]

Re: Motor boggs down at 3/4 to full throttle

I changed the floats and needle valves but I couldn't get the small caps out that cover some jets. After cleaning them,the first time,it ran perfect but after that it went back to the same. Do those cap things come out of all carbs. If so let me know and I'll get back to you. Thanks again.

 

[rickdb1boat]

Re: Motor boggs down at 3/4 to full throttle

You should be able to tap them gently to loosen them and remove them with a screwdriver. Just be careful and be easy with them. You will need to get new ones to replace those!!

 

[bob-o p]

Re: Motor boggs down at 3/4 to full throttle

i'm not sure about an evinrude but my merc was doing the very same(getting too much air or not enough fuel) but i just reduced the air to it and it runs good now (probably not the full power it should have but it runs smooth so thats all i care bout now)

 

[scotiany]

Re: Motor boggs down at 3/4 to full throttle

I don't know anything about Evinrude but, I had a lot of trouble with clogged puddle valves on my Chrysler. It had the same type symptons you have.

 

[JB]

Re: Motor boggs down at 3/4 to full throttle

Hi, Matagorda.<br /><br />One possibility that hasn't been discussed yet is heat. Not overheat, just normal heat on the ignition system. One of the common ways for powerpacks to fail is to break down when hot and work fine when cool.<br /><br />Try running her without the bonnet, to get air cooling of the ignition parts, including the powerpacks.<br /><br />Another way to troubleshoot for heat problems is to run her on the muffs, cover off, and heat the ignition parts with a hair dryer.<br /><br />Good luck.

 

[Big Al1]

Re: Motor boggs down at 3/4 to full throttle

I know when I rebuilt my old carb, I ruined the hose that connects from the crankcase to the fuel pump. My motor was bogging down when opened up and it was because of a leak in this hose. Check all fuel hoses and make sure there are no leaks. You sometimes must put a lot of stress on these hoses when removing the fuel pump or carb.