79 Evinrude 115 performance prob

[BBMerlin5091]

Ok guys, i hope ya'll can help cause i am stumped. 79 115 Evinrude sat for roughly 1 1/2 years without being run, powerhead has been rebuilt, has about 100 hours on it i'm told. After i got the boat i put it on the hose, and it would start but would only run for a few seconds and then die. Mixed new fuel for it that made a difference in the idle, it would idle but every few seconds it would spit like it was starving for fuel. Carbs right?...so i took the carbs apart, and it looks like they have been freshly rebuilt, no residue or buildup of any type, all passages were clear and needle and seat looked fine. so i put them back together and took it to the local lake, once in the water it didn't want to idle again, but once i got it warmed up a little, it ran very well other than the fact it wouldn't go above 3000 rpm's, came back to the dock and it idled beside the dock perfectly. i shut it off and started it back up, and it continued to idle fine,....i shut it down again and waited a few minutes and started it back up, and i'm back to square one, wouldn't idle.<br /><br /><br /> Totally confused

 

[prolinews]

Re: 79 Evinrude 115 performance prob

check the fuel pump take it apart carefully clean the diaphram they sometimes stick from sitting up .I bought a 140hp motor for cheap because of the fuel pump .you could pour gas into and it would run but not idle. also check the vacum line if so equipped .

 

[prolinews]

Re: 79 Evinrude 115 performance prob

also check for a pinched fuel line going to the carbs

 

[Silvertip]

Re: 79 Evinrude 115 performance prob

Since you are unsure about the amount of hours or who did the rebuild, the quality of the rebuild, or the setup after the rebuild, you need to start from square 1. 1) Compression test. 2) spark quality check 3) synch & link 4) fuel system (fuel pump output) and ignition timing. When all of that's done, and any problems corrected, a final carb adjustment should put you on the water at wide open throttle.

 

[Barnacle_Bill]

Re: 79 Evinrude 115 performance prob

I agree about checking the fuel pump, but put it back together with a kit. They are cheap and include a new diaphram.

 

[Walker]

Re: 79 Evinrude 115 performance prob

I agree, a motor that has sat for a year and a half needs the carbs cleaned GOOD, check fuel pump and all fuel lines, new water pump, change the grease in the lower ubit. new saprk plugs, and make sure the timing plate is moving forwaqrd with the throttle linkag.

 

[BBMerlin5091]

Re: 79 Evinrude 115 performance prob

Thanks guys, all excellent ideas. I'll get to work and post ya'll back with the results

 

[Dhadley]

Re: 79 Evinrude 115 performance prob

After the carbs have soaked install new OE kits. Those old gaskets may have dried out and that will cause a problem.

 

[BBMerlin5091]

Re: 79 Evinrude 115 performance prob

well i did it all,......i rebuilt both carbs, new fuel pump kit, changed oil in lower unit,.....took it out to the lake and it runs great. except that it won't get above 3000 rpms..it almost seems like the water pump is dragging the engine down more than it should, when it is on the hose and not having to pick up it's own water it's got all the power in the world but once you put it in the water, it seems like it's having to struggle to pick up water, but after it heats up everything works as it should other than the whole rpm issue.<br /><br /> lost

 

[OBJ]

Re: 79 Evinrude 115 performance prob

Dear lost..... <br /><br />The reason it runs so good on the hose is because there is no back pressure against the cylinders created by being in the water. Nearly all outboards will do this.<br /><br />Let's touch a couple issues previously mentioned.<br /><br />Did you replace the water pump? This should be done if the engine has set a while and would not hurt to replace the t-stats.<br /><br />Is the engine coming up to proper temp? You can judge this on the hose. Let it idle for a while. Then touch the flat area on top of the engine just in front of the heads. You should be able to lay your fingers on either flat area for several seconds before having to remove them. If you can't, it's overheating. If it feels cool to the touch, t-stats need replaced.<br /><br />Spark...did you look at the spark at each cylinder? Your rpms at WOT throttle suggest a cylinder not firing. The spark at each cylinder should jump at least a 7/16" gap with a hot lighting like thick spark.<br /><br />If you can fill in any of the above gaps, please do so....thanks.

 

[Walker]

Re: 79 Evinrude 115 performance prob

Pull the air box off the motor and pust the throttle all the way forward. The throttle butterflies in the carbs should be perfectly horizontal.

 

[BBMerlin5091]

Re: 79 Evinrude 115 performance prob

the butterflies are coming open all the way, thanks Walker. As this is my 1st boat, i'm not sure exactly where the water pump or the thermostats are. As for the spark, i'll get on that first thing in the morning. <br /><br /> Thanks for the help guys

 

[Solittle]

Re: 79 Evinrude 115 performance prob

If you are going to be doing your own work you need to get the OMC shop & parts manuals specific for you motor. They will pay for themselves in your first service.

 

[BBMerlin5091]

Re: 79 Evinrude 115 performance prob

I ran a compression test on the motor today, and all the cylinders were between 115 and 120. I went back and checked the spark, and found that i had two that were not firing, after checking around i discovered that the starboard powerpack was the problem with one of the cylinders, so i've ordered a new one. I also found a wire that was broken that was going to the other port powerpack, repaired that wire, and now i have spark on the port plug that wasn't firing, but it is a very weak spark, very thin but it did jump a 7/16 gap. There is absolutely no change in the way the engine runs with the plug unplugged. So my question is should i buy a new coil for the cylinder or is there possibly another problem?