1987 175 Evinrude OB surging at WOT

[rolander]

Running at wide open throttle my motor sometime surges. Normally it runs at 5200 RPM, but lately I have noticed when running at WOT I cannot get over 4500 RPM out of it and it surges, like it's running out of fuel, or a cylinder is kicking in and out. I am going to clean or replace the fuel filter on the engine. Any other things it could be? Is there any kind of issues that these motors had with the type of problem?

New plugs were put into the motor about a month ago, also fresh fuel in the gas tank and plenty of oil in the injection tank.

The engine seems to run fine when this is happening other then the surging. Doesn't seem to be missing or anything.

 

[countvlad]

Re: 1987 175 Evinrude OB surging at WOT

Running at wide open throttle my motor sometime surges. Normally it runs at 5200 RPM, but lately I have noticed when running at WOT I cannot get over 4500 RPM out of it and it surges, like it's running out of fuel, or a cylinder is kicking in and out. I am going to clean or replace the fuel filter on the engine. Any other things it could be? Is there any kind of issues that these motors had with the type of problem?

New plugs were put into the motor about a month ago, also fresh fuel in the gas tank and plenty of oil in the injection tank.

The engine seems to run fine when this is happening other then the surging. Doesn't seem to be missing or anything.

last time carbs were either rebuild or decarb? if not for a while that would probably do it...

 

[tashasdaddy]

Re: 1987 175 Evinrude OB surging at WOT

contaminated carbs, check spark and compression.

 

[emdsapmgr]

Re: 1987 175 Evinrude OB surging at WOT

You can check for a weak fuel pump. When the engine surges, have a friend constantly prime the fuel hose primer bulb. This forces extra fuel around the pump, directly into the carb bowls. If the engine runs ok while priming the bulb, the pump could be weak.

 

[kenmyfam]

Re: 1987 175 Evinrude OB surging at WOT

Give that bulb a squeeze as said already. Is your WOT RPM a little low to begin with ???

 

[rolander]

Re: 1987 175 Evinrude OB surging at WOT

Ok I have decarbed the motor using the seafoam trick, I also checked the compression in the motor, 95-100 PSI on all 6 cylinders.

The last time I had it out it was not starving, however it would only tach up to 4500 RPM at WOT. Then the next time at WOT it would tach up to 5000-5100?? I don't understand this one. I have cleaned the fuel filter, checked the vent in the tank, and checked all the new fuel line..... Starting to really wonder what the hell is going on with this thing. The motor runs perfect other then that.

 

[rolander]

Re: 1987 175 Evinrude OB surging at WOT

Oh when it's running right I am only taching around 5000-5100 RPM.

 

[countvlad]

Re: 1987 175 Evinrude OB surging at WOT

Ok I have decarbed the motor using the seafoam trick, I also checked the compression in the motor, 95-100 PSI on all 6 cylinders.

The last time I had it out it was not starving, however it would only tach up to 4500 RPM at WOT. Then the next time at WOT it would tach up to 5000-5100?? I don't understand this one. I have cleaned the fuel filter, checked the vent in the tank, and checked all the new fuel line..... Starting to really wonder what the hell is going on with this thing. The motor runs perfect other then that.

decarb sometimes its not enough... if you cant remember when the carbs were rebuild now its the time.... in order to troubleshot the problem the motor needs to be in top shape.... and unfortunately decarbing sometimes is not good enough... we need to eliminate the possibility that the carbs are dirty... it could be many reasons why your motor doesnt run very well...

have you tried to pump the primer bulb t WOT ??? do a spark gap test, make sure you have plenty of spark...

 

[ezeke]

Re: 1987 175 Evinrude OB surging at WOT

Surging can indicate an air leak in the system. Check carefully for a fuel leak by putting a little steady pressure on the primer bulb and checking everything up to the carburetors; if fuel can get out, air can and will get in.

You could also have some fuel obstruction such as a dirty anti-siphon valve. Be wary of redundant fuel filters; one full-sized water separating fuel flter is all that is needed.

 

[rolander]

Re: 1987 175 Evinrude OB surging at WOT

decarb sometimes its not enough... if you cant remember when the carbs were rebuild now its the time.... in order to troubleshot the problem the motor needs to be in top shape.... and unfortunately decarbing sometimes is not good enough... we need to eliminate the possibility that the carbs are dirty... it could be many reasons why your motor doesnt run very well...

have you tried to pump the primer bulb t WOT ??? do a spark gap test, make sure you have plenty of spark...

Yea I hear you there. I will be looking at the carbs too, First I am going to eliminate it being a fuel problem, replace all fuel line from tank to engine, replace fuel vent that comes out the side of the boat, then go from there.

Last time we had it out it wasn't surging. We did prime the bulb anyways and really made no difference. But when I went to load the boat on the trailer the engine was falling on it's face. Just like it was starving out of fuel. I would push the throttle forward to load up on the trailer and it would just die like it ran out of gas. I had to choke it to get it to finally rev up the R's and get onto the trailer. So I am thinking definate fuel issue....

When I decarbed the engine I regapped the plugs, I also have NOT had it out since decarbing, so I don't know if that has helped yet or not.

 

[rolander]

Re: 1987 175 Evinrude OB surging at WOT

Surging can indicate an air leak in the system. Check carefully for a fuel leak by putting a little steady pressure on the primer bulb and checking everything up to the carburetors; if fuel can get out, air can and will get in.

You could also have some fuel obstruction such as a dirty anti-siphon valve. Be wary of redundant fuel filters; one full-sized water separating fuel flter is all that is needed.

That's what I am thinking. It acts like an air leak or starving for fuel.

 

[emdsapmgr]

Re: 1987 175 Evinrude OB surging at WOT

Engine surging can also occur when one of the ignition components is weak. You could be dropping a cylinder. Next time you go out take an inductive timing light with you. When the engine appears to be acting up, put the timing light on each plug wire and check the flashes. Theywill indicate weak spark, no spark, or intermittent spark. Best to have the engine under load when doing this-like idling at the dock in gear. If everything appears ok, then it confirms fuel delivery as the likely problem.

 

[pasquale1968]

Re: 1987 175 Evinrude OB surging at WOT

I had a similar problem with my 1993 evinrude... i thought it was the prop seafoamed the carbs... finally fixed the problem with a screwdriver went over all the screws on the carbs and every screw seemed to work itself loose,,,,and took it out and finally got it up to 5200 rpm.... hope that helps you in some way,,,