Is the RPM myth true? AND rough idle issues...18 HP Evinrude 1968

[MotorBoatingMatt]

Hello. I recently rebuilt my carb and replaced the impeller on my 1968 18 HP Evinrude (18802A). I got it running and it seems okay, however when I lower the throttle anywhere past "Start" it sputters and eventually stalls. It barely makes it to the "Shift" setting before stalling. Any reasons why? I read the thread on carb adjustment and followed directions to no avail. Also....when IT IS idling a little past "Start" position it seems to occasionally sputter (not backfire) very quickly (slightly shaking motor) and then continue to idle. It's almost like it's having a rough time even at that throttle position to stay idle. Ideas? It has Champion plugs in right now, I plan on replacing but they don't look fouled.

Myth part: A little birdie told me that when in neutral I will not be able to hit max RPM. The "birdie" said that until I am in gear I won't be able to reach max RPMs? Is this true? I haven't tested this motor on the water yet (next weekend) because I just got it running. It seems that it isn't getting full power when revving it in neutral. The motor is in a bucket...I tried to put it in gear and test max RPM but it got real wet real fast so I stopped immediately =) I plan on taking it on the water and seeing what happens, but I thought I would see if there was any validity to this statement. Thanks for your thoughts!

 

[Daviet]

Re: Is the RPM myth true? AND rough idle issues...18 HP Evinrude 1968

First off, put a piece of tape over the start/shift decal and forget about it. You will learn to listen to the engine RPM and tell when to shift. To start it cold turn the throttle until it stops in neutral , pull the choke and start the engine.
The little birdie is correct, the RPM will only go so high in neutral, this is to keep the engine from overreving with no load on it. It sounds like you need to richen up the low speed jet a little, when you overhauled the carb did you set the low speed jet 1 1/4 turns out from lightly seated? Then you have to do final adjustment in the water. Did you remove the little core plug on top of the carb and clean all the little holes in there?

 

[MotorBoatingMatt]

Re: Is the RPM myth true? AND rough idle issues...18 HP Evinrude 1968

First off, put a piece of tape over the start/shift decal and forget about it. You will learn to listen to the engine RPM and tell when to shift. To start it cold turn the throttle until it stops in neutral , pull the choke and start the engine.
The little birdie is correct, the RPM will only go so high in neutral, this is to keep the engine from overreving with no load on it. It sounds like you need to richen up the low speed jet a little, when you overhauled the carb did you set the low speed jet 1 1/4 turns out from lightly seated? Then you have to do final adjustment in the water. Did you remove the little core plug on top of the carb and clean all the little holes in there?

Well I'm glad to hear the myth is true. I'll be sure to get that tape on there too =) If the low speed jet is the one with the knob parallel to to the choke then yes. I adjusted it to 1-1.5 out after I rebuilt the carb. Now, I'm not sure what you are talking about when you say the little core plug on the top of the carb?

That's a picture of my carb, if what you are talking about is that aluminum looking dime shaped piece at the top, than no. What implications would that have?

 

[MotorBoatingMatt]

Re: Is the RPM myth true? AND rough idle issues...18 HP Evinrude 1968

Not sure why the pic isn't showing....Here is a link to my carb picture http://www.imgplace.com/viewimg155/420/52carb.jpg

 

[Daviet]

Re: Is the RPM myth true? AND rough idle issues...18 HP Evinrude 1968

Yes, the little silver one, #25 on the breakdown below.
http://www.ishopmarine.com/ishop/js...CatFilter=BRP&eCatSupFldr=supplier-100-005-EJ

 

[MotorBoatingMatt]

Re: Is the RPM myth true? AND rough idle issues...18 HP Evinrude 1968

Yes, the little silver one, #25 on the breakdown below.
http://www.ishopmarine.com/ishop/js...CatFilter=BRP&eCatSupFldr=supplier-100-005-EJ

Yup, that is exactly the only thing I didn't clean. I still have the replacement part for that from the carb kit....So do I just take off the little silver piece and clean it up in there? I'm assuming I have to take off the carb to do that again. Since I didn't clean that part, could this be part of the rough idle problem?

 

[Daviet]

Re: Is the RPM myth true? AND rough idle issues...18 HP Evinrude 1968

If the little holes in there are plugged it will effect the idle. You should pull the carb, use an 1/8" drill bit and drill through the plug, be careful not to go to deep, just deep enough to go through the plug. Use a small punch or pick to pry out the plug. Look straight into the cavity and you should see 3 tiny holes, they must be clear. You might want to remove the low speed jet so you can blow air through all the passages.

 

[MotorBoatingMatt]

Re: Is the RPM myth true? AND rough idle issues...18 HP Evinrude 1968

Great, I will give that a try. Figures, the one thing I didn't do is what's possibly affecting the idle Appreciate the help Captain, thank you.

 

[Monte1961]

Re: Is the RPM myth true? AND rough idle issues...18 HP Evinrude 1968

Matt to take off where Daviet left off. When you get ready to replace core/welch plug, Dome side up, lightly tap with brass drift or 3/8" exstendtion".
Just enough to allow it to expand. Now with fingernail polish or omc sealant, seal the edges, just enough is good enough. And yes, that's the only way to make sure cars is fully clean. Just a reminder, lightly bottom out low speed jet, back out 1.5 turns and start. Between tiller handle and and low speed jet, get the lowest rpm possible. Once that's achieved, turn low speed an extra 1/4" out, should be good. Now go play and post back!

 

[MotorBoatingMatt]

Re: Is the RPM myth true? AND rough idle issues...18 HP Evinrude 1968

Matt to take off where Daviet left off. When you get ready to replace core/welch plug, Dome side up, lightly tap with brass drift or 3/8" exstendtion".
Just enough to allow it to expand. Now with fingernail polish or omc sealant, seal the edges, just enough is good enough. And yes, that's the only way to make sure cars is fully clean. Just a reminder, lightly bottom out low speed jet, back out 1.5 turns and start. Between tiller handle and and low speed jet, get the lowest rpm possible. Once that's achieved, turn low speed an extra 1/4" out, should be good. Now go play and post back!

Thanks Monte, I'll be sure to to post back once I implement all this great advice this upcoming weekend. I didn't know you had to seal that core plug. Is that necessary or just a way to ensure better performance?

 

[Monte1961]

Re: Is the RPM myth true? AND rough idle issues...18 HP Evinrude 1968

No it's not necessary, but I as well as others would recommend it. Cheap insurance is really what it is. Should you have a small air/vacuum leak, that alone would take care of it.