89 140 looper, half power

[Ken Barber]

Can anyone suggest where to start?

1989 140 Evinrude Looper, always ran great. Last week, it began surging while trolling at 800 RPM. It would just kick up a little faster for 20 or 30 seconds, and then go back to normal. Not sounding right, that is for sure.

This week took it out and it lost half of the power. WOT resulted in only 2000 rpm, so I had to turn back, only to have full power restored for a short while, then back to half power. It also sucked my tank almost dry in a very short while, so I am assuming there was plenty of expensive gas just flowing though the cylinders.

Where should I start -plugs, Carburetors or head gaskets are all things folks have mentioned.

Thanks for your help.

 

[CharlieB]

Re: 89 140 looper, half power

Always test spark quality first to determine if it is an ignition problem or a fuel problem.

Remove the airbox, pump the primer while observing the carb looking for any flooding in any carb.

Either a part of the ignition fails, dropping one or more cylinder, or possibly the fuel pump has worn a small hole in the diaphragm and raw fuel is leaking into the engine by the vaccuum pulse hose to the crankcase. Disconnect either end of that hose, wipe a Q-tip inside, look and smell it. Is it wet with fuel?

 

[tashasdaddy]

Re: 89 140 looper, half power

spark and compression check first. buy a service manual.

 

[crb478]

Re: 89 140 looper, half power

Start with a compression test, followed by verifing that you have spark to all four cylinders. Then make sure it is getting fuel to all four cylinders. If it is getting air spark and fuel it should run unless you have some type of mechanical failure.

The compression test should be over 100 psi and within 10 persent of each cylinder.

The spark will let you know that there is a source to ignite the fuel.

If both of those check out you can crank the motor and start pulling plug wires to see if it makes any difference in the way the motor runs. The cylinders that do not change the way it is running are the ones where the problem is. You can also spray premixed fuel from a spray bottle into the carbs with the engine running and see if doing so makes the engine pick up and run better. If it does you likely have a fuel or carb problem.

 

[mikesea]

Re: 89 140 looper, half power

all of the above and ,check for water in your gas

 

[ezeke]

Re: 89 140 looper, half power

You have a S.L.O.W. powerpack, so when your engine overheats, it cuts you back automatically by disabling half the cylinders.

S.L.O.W. will not reset until the engine cools and is turned off and restarted. Continuing to run will supply all cylinders with fuel and oil but only half of them will use it

BTW, Pulling spark plug wires off the running big bore loopers will kill the powerpack. Use a inductive timing light instead.