Mercury 115 no power

[trmelvin]

I have an early 1980 Mercury 115. The engine idles great and when you excelorate it feels like it is going to do something but fall on its face and will die if you don't come off the throttle. I,ve gone thru the carbs and fuel system and that is all fine. I also noticed the tach is not right. Could this be a stator problem? Any help would be appreciated. Thanks

 

[strathcona99]

Re: Mercury 115 no power

I had the exact same problem and symptoms with a Honda Civic. I realize this is not a marine engine but I think its worth the read. The problem with my civic was a tracking (shorting) ignition coil. Using an ohmeter the coil tested fine and even from the eye looked good too. After changing the coil my car came back to life.

I have a 115 Merc as well. Let me know what you find out.

Hope this helps.

 

[79Merc80]

Re: Mercury 115 no power

I have a 1984 Mariner 90 (Basically the same engine). When I got it she would idle great and run up to about 2500 RPM's and then fall on her face. Turned out to be the stator. It was sending erratic voltages to the power packs and caused #1 to fire intermittenly above 2500 and #3 to shut off completely above 2500.

Hope this helps.

Craig

 

[Maxz695]

Re: Mercury 115 no power

not for nothing but try disconnecting the tach I have read a post where the tach affected the engine when bad may be nothing but worth a try

 

[trmelvin]

Re: Mercury 115 no power

Thanks for the info, I think I will order a new stator. I did disconnect the tach and it seemed to get better. If any one has any more info please let me know. Thanks again.

 

[444]

Re: Mercury 115 no power

Disconnect the rectifier and tape up the ends. There's a seperate stator for the ignition system and charging system, but when the charging system goes, it for some reason affects the ignition system. My charging stator went bad, causing it to kill rectifiers, and the combination of the two caused a poor run condition very much like you describe.

 

[CharlieB]

Re: Mercury 115 no power

Assuming that your problem is a stator and spending money to throw parts at the problem often ends up costing you a LOT of money on needless parts.

Need to know model & serial #'s to be sure which ignition you have.

Distributor models it won't be the stator, you'll find the problem in the carbs.

Non-distributor/switchbox models you need to check for spark on EACH cyl.

2 + 2 4 cyl models you need to check accelerator pump and injector nozzles.

Which system do you have?

 

[trmelvin]

Re: Mercury 115 no power

It is a 115 hp mercury Serial# 5725778. It is distributor less model. I will go and check if there is spark on all six cyl. But it does idle beautiful. I'll be honest, I don't want to needlessly throw money at it either. Is there a way I can test the stator? Can someone send me the procedure? Thanks!!

 

[trmelvin]

Re: Mercury 115 no power

Looks like I have a bad switch box. Any way to test them?

 

[bktheking]

Re: Mercury 115 no power

Hit the cdi electronics site and lookup the tests for your motor.

 

[trmelvin]

Re: Mercury 115 no power

Thanks!!!

 

[trmelvin]

Re: Mercury 115 no power

Is that on this site?

 

[bktheking]

Re: Mercury 115 no power

http://www.cdielectronics.com/downloads/troubleshooting guide/

 

[ebrich2]

Re: Mercury 115 no power

i had a similar problem on my 88 150 xr4, would not go past 1800 rpm but idled beautifully, check spark and found three cylinders not firing, replaced switch box and now she runs like a dream.

 

[Chris1956]

Re: Mercury 115 no power

TRMelvin, This thread contains a lot of wild guesses as to your problem. Let's be methodical, and find out the issue before replacing anything. Take a compression test and test for spark on all cylinders. Post the results. Provided those are good, it is likely you adjusted the carbs too lean when you cleaned them. It happens all the time.

 

[bktheking]

Re: Mercury 115 no power

Sounds to me like the carbs idle circuits running too rich coming off idle, search clams canino's write up about timing an inline 6, not for the timing part but the carb part, he explains it clearly.


http://forums.iboats.com/showthread.php?t=128495&page=1

Here it is!

 

[trmelvin]

Re: Mercury 115 no power

Engine compression 120lbs on all six, No spark on # 4 cylinder, Checked coil pack by switching wires with #4 and #5 between coill pack and switch box and seems to be a switch box failure. Stator tested fine....... for now. I ordered a new switch box, I'll let you guys know what happens. Hope it gets here before the weekend!!! Thanks for all the info!!!

 

[Chris1956]

Re: Mercury 115 no power

BK, I have never found a case where the carb idle mixture was set too rich. If that were to happen the motor would not idle, or at least would not idle for very long (few seconds). What happens is that folks tune the mixture to achieve highest idle RPM. Now the mixture is too lean to allow acceleration. In that thread Clams says to adjust idle mixture to optimum, and then open the mixture needles 1/4 turn more. Here is the excerpt:

"Now, re-adjust the idle screws, in to stumble, then 1/2 turn out. When you've gone back and forth with that a few times and have it "perfect" - adjust each one out 1/4 turn."

 

[trmelvin]

Re: Mercury 115 no power

I get my part today!

 

[bktheking]

Re: Mercury 115 no power

OK well maybe too lean, I went through this same thing last night, it took me 45 minutes at the launch before it would stop falling on it's face. I just know if it isn't bang on when it comes to those 3 carbs the same symptoms will occur.