No power at WOT

[John Lapic]

I have a 1971 Johnson 9.5. It idles fine and is smooth at slow speeds. At WOT it seems I am only at about 3/4 speed or RPM. It does not bog down, just won't open up. I ran it for several minutes at WOT, and at one point it took off, only to stall shortly after. I had trouble restarting and noted a loss of pressure in the fuel line bulb. I pumped up the fuel line with the bulb and it started fine, just no power again at WOT. Any suggestions?

Also, I am about an hour to the nearest water. Can I open up the throttle in a barrel? I have a 40 gallon drum that I can use, but have heard it is not good to run it much above idle. Something about running away. I am a novice here so any help is appreciated

 

[ezeke]

Re: No power at WOT

If you have a large enough test tank to run the motor in forward gear, you could take the engine above the stop that should keep you from running too fast in neutral. It would be better to use a test wheel. Otherwise you should not run the motor up without a load, it can runaway and destroy the engine.

Sounds like you may be overheating. The motor needs to deep enough in your barrel to cover the waterpump, which means just about at the outer surface of the midsection. Test for overheat by placing your fingers on the cylinder head. You should be able to keep them on the head for a full three count anytime the engine is running. If you can't check the thermostat since you have already done the water pump impeller.

With the engine off, put the motor in forward and turn the tiller to WOT. Then look down the carburetor throat and see if the throttle plate is really wide open.

 

[John Lapic]

Re: No power at WOT

I'll check the cylinders for overheating. You are right, I did change the impellor and am getting plenty of water out the pee hole. Is that any indication of thermostat operation?

 

[ezeke]

Re: No power at WOT

The water that comes through the exhaust relief tells you that the water pump is working.

The water that is inside the engine starts and stops as the thermostat opens and closes, responding to the engine temperature rising and falling.

The thermostat is open at about 143 degrees if it works. If it does not work, the water does not circulate through the engine's cooling passages, the engine overheats, binds and stops.

 

[John Lapic]

Re: No power at WOT

OK I ran it at idle for 10 minutes in a barrel. The cylinders barely got warm. Any ideas?
Also, I looked down the carb throat at WOT. The plate is at about 11:00, not wide open. Would that make enough of a difference?

 

[ezeke]

Re: No power at WOT

If the cylinders barely got warm your thermostat is probably stuck open so your motor is running cold all the time and probably needs a decarb.

What are the compression readings?

About now I'm thinking that your high speed jet is probably clogged. It is just behind, and in line with, the drain plug on the float bowl. Because of that location, it tends to pick up all the junk that sinks and any gel that comes through.