4hp Evinrude throttle problems

[Emery]

I have a 4hp 2-cilinder Evinrude outboard from I think 1984. (model no.: E4BRCRM). I got it starting after it had been in someone's garage for a year or so.

I put new gear oil in the lower unit and I cleaned the carb. I put fresh fuel in the tank and it started fine. I put it behind my boat for testing and it would start fine but once I opened up the throttle, the motor would not rev up to full speed. It would get up to about half power and then not run very well. Also, when the motor is in neutral it will rev up a little further than when in gear (but still not full power), and then when I put it in gear it revs down to a lower speed by itself and sort of stays there.

The person from who I bought the motor said he had a new carb put on for some reason. The new carb has the choke handle on the right side of the carb instead of the left side.

It's a cute little fishing motor and still looks great. It would be great if someone could help me with this problem.

Thanks!

 

[JB]

Re: 4hp Evinrude throttle problems

You might have a problem with the throttle plate not opening fully, Emery, but it is more likely that you are making power with only one cylinder.

Try disabling each spark plug in turn. If one kills it and the other has no effect you have a dead cylinder.

Some possible causes are:
*no spark to that one.
*failed reeds.
*low compression.
*leaky bypass cover.

If both cylinders are making power you might have:
*incorrect carb with too small venturi.
*linkage to carb not correct.
*incorrect jetting in carb.
*incorrect timing.

I don't remember if the '84 models still used a magneto ignition but if it has a mag loss of spark could be points, condenser.

 

[F_R]

Re: 4hp Evinrude throttle problems

JB said it well. Follow his advice.

 

[Emery]

Re: 4hp Evinrude throttle problems

JB, thanks for the detailed answer. The throttle plate opens up all the way, I have checked.

I was also thinking of a dead cylinder but the engine starts on each spark plug when I disable them in turn. So they both spark.

So now when both cylinders are making power I might have:
*incorrect carb with too small venturi.
*linkage to carb not correct.
*incorrect jetting in carb.
*incorrect timing.

*incorrect carb with too small venturi.
The carb could have a too small venturi, but when I start the motor and I open the throttle all the way, it will run at full speed for about 3-4 seconds and then go back to about half power with the throttle-lever staying at full speed.

*linkage to carb not correct. I've checked the fuel line that runs to the carb and it seems fine. The tank is totally clean and so is the carb. One thing I did notice just now was that there isn't a gasket between the carb and the motor. I'm guessing there should be one there just like as on all other engines... But that missing gasket shouldn't be the reason it's running this way, should it?

*incorrect jetting in carb.
That could be the problem. Although the carb is clean, I don't know how far in or out I should set the adjusting screws to.

*incorrect timing.
Could also be the problem but It looks like nobody has ever looked under the flywheel of this thing before. I could take a look at this but I don't know if it has a magneto igniton or not. And if it does, could you tell me what the correct gap between the points should be?

Thanks again so much for your great help so far.

Emery.

 

[ezeke]

Re: 4hp Evinrude throttle problems

Fouled high speed orifice.

http://forums.iboats.com/showthread.php?t=167352

 

[F_R]

Re: 4hp Evinrude throttle problems

You say it runs full speed for awhile then cuts back to 1/2. That smacks of an ignition problem. It's dropping a cylinder. Remove and ground one wire at a time and run it at full throttle. The one that's dropping will drop and kill it.

Points are set .020" at widest opening on the cam.

 

[Emery]

Re: 4hp Evinrude throttle problems

I am going to take a look at the ignition but how do I get the flywheel off to get at the ignition?

I've looked through the carb and everything seems to be clean. I did manage to break off the end of the idle adjustment screw by screwing it in too far. Not a big problem, I can still get it starting.

Thanks for the help so far.

 

[F_R]

Re: 4hp Evinrude throttle problems

You need a 3-bolt puller (like a vibration damper puller). Use ONLY grade 8 bolts with it. Remove the flywheel nut and the 3 bolts go into the holes near the center of the flywheel. Screw them in 7/16" no more, no less. Tighten the puller center bolt and it will pop off. Don't be timid, it takes quite a bit of tight to get it to pop. A strap wrench helps to hold the flywheel from turning . When reinstalling the flywheel the shaft and flywheel tapers must be clean and dry. A torque wrench should be used to tighten the flywheel nut to 30-40 ft/lbs. If you don't want to obtain or borrow the tools, go ahead and muck it up. Note: some auto parts stores loan or rent tools.

 

[Emery]

Re: 4hp Evinrude throttle problems

Ok, I made a 3 bolt puller myself and I got the flywheel off. Could you tell me what I should look at inside the ignition and what I should adjust things to?

Thanks so much.

Emery