sluggish 115 hp engine

[tn]

I have a 1996 115 hp johnson.It's on a 1997 larson sei 186. At wot it runs around 42mph with a tach reading of 5200. This is with trim set at mid to up range.prop size is 14x17. even though it's running at 5200 rpm the motor seems sluggish at wot and has a slight miss/surge.I changed out the plugs and on cylinder #4 the plug was dry and had a brownish color,the others were wet and blackish. Any suggestions as to what may be going on? Thanks

 

[JB]

Re: sluggish 115 hp engine

Moving to Johnson Troubles.

 

[The Marine Doctor]

Re: sluggish 115 hp engine

You might be running lean on #4.<br /><br />Remove and rebuild the carbs.<br /><br />TMD

 

[Solittle]

Re: sluggish 115 hp engine

http://www.outboardrepairs.com/carburetors/

 

[OBJ]

Re: sluggish 115 hp engine

Hey whoderr....could post the complete model number please?<br /><br />Can you give us a little history lesson here? Is the motor new to you or have you owned it for a while? <br /><br />If you have owned it for a while, is this problem a new one? What was the original WOT rpm?<br /><br />Have you had the compression tested lately?<br /><br />May also be a good idea to check the ignition system out and make sure all cylinders are sparking a hot blue spark across at least a 7/16inch gap.<br /><br />Is the engine running a normal temp? At idle, you should be able to lay your finger on the flat place ontop of the block just behind the head and leave it there for several seconds before having to move them.<br /><br />Keep us posted....thanks!

 

[walleyehed]

Re: sluggish 115 hp engine

I would have to agree with most of the above but I can tell you on MY crossflow 97' 115, I'm running one step richer on that (#4) side of the bottom carb......it's the only way I get all 4 plugs the same color-(indication of mixture).<br /> You got 2 good replies-TMD,& OBJ....carb link is good too, don't get me wrong, but if you can answer OBJ's questions, that will give maybe some tell-tails......Good Luck!

 

[tn]

Re: sluggish 115 hp engine

Thanks for the replies. The model number is G04146971. I just purchased the boat so I have no history. Waiting on my service manual to arrive. I have not checked the compression but plan on doing so. Will also check the spark as suggested as well as the finger test. What's really weird is I thought I had changed out all the plugs but I apparently left # 4 cylinder in with the old champion. I bought Denso plugs and had 3 new Denso's in and 1 old champion. When I realized this and changed the old champion out it ran worse.WOT was 35mph with rpm of 4200. I put the old champion back in and it ran like before. I guess this motor doesn't like Denso plugs. Will go back with all champions.

 

[tn]

Re: sluggish 115 hp engine

Sorry guys I gave you the serial number instead of the model number. The model number is J115TLEDA.

 

[walleyehed]

Re: sluggish 115 hp engine

Amen, on the Champions, and gap at .035. You may want to pull #4 jet out and clean to make sure you don't have crap in that jet as well.....

 

[tn]

Re: sluggish 115 hp engine

Well after checking the compression which is good. All cylinders were in the 125 to 122 range. I also ordered new carb kits. I decided to decarb the engine. Bought some OMC tuner and did what it said to do. The engine is now running smooth and not surging or missing. The tuner did the trick. Thanks for everyone's imput.