Evinrude V4 down on power

[highcotton59]

I have a 1990 Evinrude 88HP SPL outboard. I just purchased this motor and it is installed on a 20? pontoon. The problem I am having that it seems down on power. This is what I have done to determine what might be wrong. I checked the compression it reads 107-120-120-115 on the cylinders, I believe that is probably OK, but your opinion is welcome. I pulled all the spark plugs and one seemed to be in newer condition that the other three. I replaced the plugs with new ones, ran the boat on the water for an hour at different speeds and pulled the plugs again. One plug looks like new (white and shiny), the others looks smokey and slightly wet (normal looking). I reinstalled the plugs and put water on the engine and pulled the plug wires one at a time while running, the cylinder that has the new looking plug does not affect the rpm or falter the engine when that plug wire is pulled, all other plug wires have an effect on the idle and make the engine falter. I checked the fire at each plug and it looks very good. I suspect this one cylinder is being starved for fuel. If so, would a carb rebuild most likely fix it? Could I have a reed problem for that one cylinder? Is it likely something else? Any suggestions would be much appreciated. Unfortunately a tach is not on this boat, so I can?t use that as a troubleshooting tool, but I will be installing one soon.

 

[bktheking]

Re: Evinrude V4 down on power

Could be a reed issue or water getting into the cylinder causing the plug to be water washed.

 

[Dennisanoka]

Re: Evinrude V4 down on power

To see if it is getting water in I would try two things. First put one of the other plugs in that hole and run it. When you pull it out it may be easier to see if it's been steam cleaned or also use a flashlight to look in the hole when that piston is in the closest position and see if the piston head looks real clean compared to the others. Otherwise I'd be looking at the carbs next.

 

[highcotton59]

Re: Evinrude V4 down on power

OK - IF it is water washing of the cylinder and plug, what is the fix? head gasket? Any others out there with an opinion?

 

[Dennisanoka]

Re: Evinrude V4 down on power

Sometimes you don't know- until you know. I suggest starting with determining IF that is even the issue then start looking at possible fixes. Why spend time on all the different scenarios until you even know what the issue is? For instance I've heard of a cracked block which would be horrible but you don't want that so please go see what you can find out then start digging but pulling the head is easy and not expensive and may tell you a lot.

 

[highcotton59]

Re: Evinrude V4 down on power

OK - will check for water washing in that one cylinder, then will consider the fixes. Thanks for the advice.

 

[emdsapmgr]

Re: Evinrude V4 down on power

You can check the spark while the engine is running by using an inductive timing light. Once you establish the plugs have fire when under compression, then look for other issues. You could have a blown head gasket. Not expensive nor hard to replace. Water can also get into the cyls from the leaky exhaust covers which leak water into the exhaust chest. You may also have a fuel restriction in the carb throat that feeds that cyl. If this is the case, that piston is also not getting oil-not a good scenario at all. You may need to tear that carb down and inspect the jets for obstructions. I would not run the engine till you know it is not a fuel delivery problem.

 

[kenmyfam]

Re: Evinrude V4 down on power

Can you post a photo of the plugs ???

 

[highcotton59]

Re: Evinrude V4 down on power

OK - this is what I have done on the troubleshooting side. I swapped the plugs around to determine if the suspect cylinder would whitewash the plug from steam cleaning, it didn't. It still appears that this cylinder is not making power due to the fact when I disconnect the plug wire from it the motor does not falter or change RPM. All the other plug wires when removed one at a time make the engine falter and reduce RPMs while idling. Would the spark that is showing on the plug outside the motor change under compression, not sure I understand that theory?

 

[bktheking]

Re: Evinrude V4 down on power

Throw a timing light on that plug wire and watch the flashes, may an intermittant problem caused by a bad trigger coil, coil etc etc.

 

[ezeke]

Re: Evinrude V4 down on power

Inspect the four ignition coils carefully and clean the ground connections well. If an ignition coil appears discolored, cracked, swollen or if the potting looks melted, replace it.

As emdsapmgr indicated, you should use an inductive timing light because it will immediately disclose any firing deficiency on a running engine.

 

[highcotton59]

Re: Evinrude V4 down on power

OK - I didn't have a timing light but I did this. I pulled the plug and left the plug wire attached. I started the engine and grounded the plug to the block - I am getting a very strong consistant spark across the gap on that plug. I believe it is firing the way it normally should. Was this a sufficient test?

 

[ezeke]

Re: Evinrude V4 down on power

You need compression, fire, fuel and air. Which one do you think is missing?

 

[highcotton59]

Re: Evinrude V4 down on power

Looks like a carb rebuild is in order...

 

[emdsapmgr]

Re: Evinrude V4 down on power

If you are going into the carbs, I'd pay close attention to the carb and it's barrel which feeds your problem cylinder. It is always possible that you have a piece of dirtdebris lodged in the main jet. Pull out all the jets and visually inspect them during overhaul. I've seen everything from dirt to fuel hose in the jets.