1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

[QuackAddict84]

Hey guys - I'm working on a 1977 4 hp Evinrude model 4706B. I picked the motor up in non-running condition, with a new water pump and "brain box" installed on it - previous owner still couldn't get it running. I noticed when examining it before purchase that the high speed idle jet was screwed all the way in. I rebuilt the carburetor, and got it started. It seemed to run ok on the water, but felt a little bit sluggish for what I expected a 4 horsepower to do (more like a glorified trolling motor.) I did notice that I also had to gently seat the high speed needle to get it to run at WOT. I did back it out a 1/16 to an 1/8 turn to avoid damage from lean mixture. I put a couple hours on it and decided just wasn't very powerful. When I went to winterize it, I noticed something interesting. The top spark plug was a little dirty (not more that expected for a few hours of run time), but the bottom plug looked like I just pulled it out of the box - brand new. It was not soaked with gasoline, just very, very clean. I though maybe it wasn't firing, so I rotated the engine with the plug outside touching ground, and the coil is firing it just fine. Both cylinders have equal compression - around 65 or 70 if I remember correctly. Is it possible that it isn't getting any fuel into it? What could be causing this? Thanks for any help; I greatly appreciate it.

 

[Rick.]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

I would suggest you get a spark gap tester and see if in fact it creates a strong enough spark. Spark should jump 3/8th. of on inch and be blue/white and very snappy. It could be getting a weak spark which would be even worse under compression. These are usually very good little motors but they are (IMO) more of a trolling motor. Your not likely to ever plane a 12ft. with one. Another thing I wonder about... do you think the previous owner might have swapped the high and low speed needles? I'm not certain that is possible but worth looking into. Best of luck. Rick.

 

[QuackAddict84]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

The needles are quite different, they couldn't be swapped. Is it possible this is being caused by a sticking reed? Thanks.

 

[tashasdaddy]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

"I just pulled it out of the box - brand new". possibly steam cleaned, water intrusion into the cylinder.

read the TOP SECRET FILE.

 

[QuackAddict84]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

How can I check for water intrusion? Which heading on TOP SECRET are you wanting me to read? Also, is that a no on the sticking reeds? Thanks so much for your help.

 

[raczekp1]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

water intrusion=water in cylinder,usualy from cooling system,its easy to notice becouse plugs are water wet, it hapens when head gasket is bad,leak in the head gasket.
if water gets into cylinder so spark just stop firiing.
reeds its a leaf valve located in the intake mainfold, the part of crankcase that carb is atache to.
i think you have very low compresion.
my old 6hp had almost 90

 

[QuackAddict84]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

If wet spark plugs is the only way to find water intrusion, I don't think that's it. The plug is not visibly wet when removed. I can change the head gasket to make sure though, because that may be causing low compression as well. I thought the compression was a little low, but I've never worked on a motor that small. Thanks so much - any further input is greatly appreciated.

 

[Rick.]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

The needles are quite different, they couldn't be swapped. Is it possible this is being caused by a sticking reed? Thanks.

Well that rules out the needle switch theory. I highly doubt a reed problem exists. I'm still thinking lack of quality spark. I looked at the top secret file and didn't see anything obvious about water intrusion. You would normally see a white smoke in the exhaust if water is in a cylinder. Keep trying. Rick.

 

[QuackAddict84]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

The exhaust for this motor is located below the level of the water intake. Also the exhaust relief seems to serve also as the telltale sign for the water pump function. Because of this, I feel that confirming water intrusion to be the problem would be quite difficult. That being said there is no obvious signs of steam or white smoke coming from the exhaust relief/telltale. I don't know of any way to observe steam coming from the actual exhaust because the water pump would need to be submerged while the engine is running to observe this. If there is any technique that I'm missing that can be used to confirm water intrusion I would greatly appreciate further instruction. Thank you so much for all of your assistance.

 

[QuackAddict84]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

Also, the spark produced by both coils appeared quite strong. I would think that a cylinder with adequate fuel supply and weak spark would become fouled out and have an oily plug. Am I at all correct in feeling that way?

 

[Tim Frank]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

Also, the spark produced by both coils appeared quite strong.

If you checked with a proper spark tester as was suggested, great.
If you just grounded the plugs against the engine, you still have not tested the spark quality ...

The term "appeared quite strong" is not really useful in troubleshooting this kind of non-run issue.

This simple tool is less than $10- for a perfectly serviceable one, and it will save you many hours and $$ in a short time.

 

[QuackAddict84]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

Tim- As you suspected, I simply grounded the spark plugs to the engine block. I was not aware this is an unacceptable way to test spark. I will go purchase a spark tester and test the spark from both cylinders appropriately and post the results. Thank you very much for the tip.

 

[QuackAddict84]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

Hey fellas, sorry for the slow reply. I finally got around to testing the spark on this motor. Both cylinders' spark jumps across a 3/8 gap. In a dark room they both appear a purplish blue color. Any more suggestions? Thanks again for any help; it is greatly appreciated.

 

[Will Bark]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

Try decarbing the engine to see if compression will rise, your rings may be sticking. Go to top secret files and look under decarbing; it will tell you how to do it.

 

[Rick.]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

Sounds like your spark is fine. Next thing I would try is pulling each plug wire (one at a time) while motor is running at idle. If you have a cylinder not firing you will notice no difference when that wire is pulled and the motor will shut down when you pull the wire of the cylinder that is firing.

"around 65 or 70 if I remember correctly." You need to be certain and if your memory is anything like mine, you don't remember correctly. When I check compression I always write down the numbers. Rick.

 

[QuackAddict84]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

I decarbed the motor right after I rebuilt the carburetor, before I ever put it on the water. As to compression, I know it was between 65 and 70, but I don't remember exactly. I checked it before I bought it, and we were standing out in the rain, so I didn't take the time to write down the numbers. The engine was not warmed up, and hadn't been run for about a year prior to compression check. Should I repeat the compression check?

Once again, thanks.

 

[Rick.]

Re: 1977 Evinrude 4hp Fuel/Ignition/Mechanical Problem

Not if your sure about those numbers. I would check it again after you've had a dozen hours of solid run time just to see if it improves though. For now just pull the wires like I suggested. Rick.