96 Johnson 50 Rough Idle?

[ShellBack101]

I just bought a 22Ft Crest II pontoon with a 1996 Johnson 50hp 2cycle 2 cylinder on the back (VRO). I have never owned an outboard before, only I/O's. it seems to be very rough at idle, and smokes a bit compared to other outboards I have seen around the lake. At times feels like it may stall when engaged, but runs great around 4000 rpm I have changed the plugs, fuel filter, and used the Johnson Evinrude decarber. <br />My questions are;<br />1) How smooth do outboards idle, should I be able to feel the vibe through the boat?<br />2) What is a good Idle RPM for this motor. <br />3) What top end speed & RPM can I expect out of this motor / boat combo. <br />4) Any suggestions advise welcomed. thanks in advance

 

[fireman57]

Re: 96 Johnson 50 Rough Idle?

First of all welcome to iboats.<br />1. That engine should idle very well and you should not feel a lot of vibration through a pontoon of that size.<br />2. Usually somewhere between 650-800 rpms. I believe that most guys here will tell you between 700-750.<br />3. Don't know but would just guess around 17mph. Strictly just a guess.<br />4. If it feels like it wants to stall when you engage the gear and the idle is rough I would suspect that you have some crap in one of your low speed jets in the carbs. Kits run about 20.00 and are easy to install. Do a search on rebuilding carbs with the red search function at the top of this page and you will do fine. Pretty easy job just make sure that they are perfectly clean and blown out with compressed air.

 

[ShellBack101]

Re: 96 Johnson 50 Rough Idle?

Thanks Fireman, I apprecaite the info, at WOT I have been getting around 18MPH according to handheld GPS (boat speedo not working right), I will have to grab a kit at the local marina. I appreciate it.

 

[phatmanmike]

Re: 96 Johnson 50 Rough Idle?

you have an omc twin, wich means you have 2 cylinders. they are NOT a very smooth creature to begin with. the more cylinders you have, the smoother its gonna be.<br /><br />you need to be getting 5500 rpm wot with that motor. if your not getting full WOT, then you need to check you throtthle cable for slop/ play, and also check that your carbs butterflies are opening all the way when you "floor" it.<br /><br />maybe your idle rpm is a bit low, that would also cause it to stumble and vibrate.<br /><br />get yourself a service manual from iboats, your local library, or do a search for ken cook manuals

 

[fireman57]

Re: 96 Johnson 50 Rough Idle?

I don't know that he can get 5500 like he should pushing that heavy a boat without changing props. Myobs I agree with you on the more cylinders for smoother idle but I got my '83 50hp to idle very smooth with no shake on my little 14.5ft fiberglass. Runs right at 31mpg with GPS with 2 full growns in it that is why I was guessing 17mph. My '91 25hp would get both of us up on plane but if I added a third person it wouldn't make it and we just plowed. I'm guessing that the bigger boat with more drag will not get the rpms it should have just like my 25 wouldn't because of the load. I could have gone lower pitch on the prop but the speed would have suffered. I would have liked the high rpms on the 25 for the engines sake but I was underpowered to start with.