9.9 evinrude dropping from high speed

[Wolf359]

Hi all-

I have a 1980 9.9 hp evinrude that I recently aquired. The motor runs great at slow speed but when I open the throttle it will run at high rpm for a few seconds and then drop to low rpm. If I again return the throttle to wide open, the rpms go up and then down again. Pumping the primer bulb seems to help somewhat but will not return the motor to full speed. Plugs, fuel tank, fuel line and gas are new and the fuel pump appears to be functional. Also, the motor is being run in neutral with the hose attachement. I want to make sure it works before I get it on the water. Any help would be great.

 

[rolmops]

Re: 9.9 evinrude dropping from high speed

Welcome to iboats.
First and most of all.Stop trying to run your engine at full rpm out of the water!!!
When you have no water resistance on your exhaust,it is quite possible for the engine to "run away".This means that it will go into very high RPMs and the engine block may just throw a piston or worse.
It is much better to just take your boat to a launch and start the engine in the water and then with water resistance on the exhaust system,even when only having the engine on neutral you can get a much better idea of what the engine does.It may be that the problem will just not be there anymore.