1983 Merc 115 no power

[Ski'nBlind]

Hi all,
I wanted to send out a shout to everyone that has posted about Mercury service and repair. I've been away from boating for a decade and just recently bought a Checkmate with said Merc "tower of power". This set up has been sitting for years and it took me weeks of searching this forum for answers. If you look hard enough this forum has way more info than my seloc manual but it works for quick reference.

I initially had a problem with "motor won't rev past 2500 rpm" like hundreds of others. I overlooked an issue when I bought the boat that some of the wiring (stator ac and pri. coil wires) looked good on inspection but completely fell apart and broke while testing. The engine would start and idle great in the driveway but had no power under load. I did the test of disconnecting the 2 yellow stator leads from the rectifier and the engine took off like a raped ape out on the water. There was some issues I found in my searchs here that some people think that since it's the charging system only it won't effect ignition......WRONG! In case there's someone out there with a similar problem it took a whole 5 minutes to figure out while at the dock.

The rectifier did not test bad with my fluke meter so I was a little surprised at the results myself. I also purchased a new CDI stator since I had done quite a bit of re-soldering wires just to be able to acurately test the ignition/ charging system.

I removed the idle stabilizer too after reading about that and am waiting for the rain to stop to go adjust the timing. Lots of very good information on this site!!

Thanks all

 

[arsenalpsu]

Re: 1983 Merc 115 no power

sounds like you weren't getting spark on all 6. If you don't have the correct voltage on your system that can affect it (the rectifier charges your battery and sends info to your tach), but your problem may have been solved by replacing the stator.

 

[Ski'nBlind]

Re: 1983 Merc 115 no power

Exactly, it was a hig speed miss. I repaired and made new wires to the coils and stator and any other wire that was corroded but it did not fix the problem. I removed the idle stabilizer but that didn't help either. I did have good voltages and ohms per specs in the driveway but I couldn't take readings out on the lake on my own. The battery was charging (slightly). 12.86 volts at idle climbing up to 13.4 at 1500 rpm once fully warmed up.

I read CDI's troubleshooting page and saw the test of disconnecting the yellow stator leads off the recifier and re-testing the boat. Very simple to do and pinpointed a problem with just a 3/8" nut driver and some electrical tape. I understand how diodes/ a rectifier works and was surprised that the boat jumped out of the water just by removing the 2 yellow wires (but not charging the battery now).

I installed the new stator and rectifier and set my max timing at 21 deg's. Spec says 5-7 BTDC for the intermediate timing but the motor didn't seem to like that too much. I set it at 3 ATDC and it idles very smooth with the linc and sync done. Not sure about that, any clues? I'm taking it out on the lake this week and will bring my timing light just in case it bogs on holeshot.

 

[arsenalpsu]

Re: 1983 Merc 115 no power

I installed the new stator and rectifier and set my max timing at 21 deg's. Spec says 5-7 BTDC for the intermediate timing but the motor didn't seem to like that too much. I set it at 3 ATDC and it idles very smooth with the linc and sync done. Not sure about that, any clues? I'm taking it out on the lake this week and will bring my timing light just in case it bogs on holeshot.

My OEM book says 5-7 ATDC for PRIMARY PICKUP timing. Your idle timing "is what it is" to get idle at or below 1000RPM. If you bog on a hole shot you won't need a timing light, just turn each carb out 1/8 turn and try it again. If she still does it keep doing this until you can get one. This may make your idle a bit rough but then you won't be running lean at WOT.
(lean running makes for a nice idle but an expensive rebuild)

OH- and did you put a BB in the small rubber hose that is on the top of each carb? This is a midrange air system that lowers your fuel mix at midrange speeds. It was a fuel saver back in the day but also leads to a lean mix, when you put a BB in there it disables it. I recommend all tower owners do this.

 

[Ski'nBlind]

Re: 1983 Merc 115 no power

WOW, thanks for that. I now realize how bad a Seloc manual is. That's a huge difference. It idled so bad at 5 BTDC i had to go back and double check the manual. Watching it bounce around trying to keep itself running wasn't pretty plus the adjustment screw was at its limit... I knew something wasn't right. I thought maybe it was the spec for the idle stabilizer connected but I was at 700 rpm (above the 550 cut-in point anyways). I will set it right in the middle at 6ATDC deg's now that I know and see how she idles.

Yes, I will be playing with the mixture screws and richer is better. I was actually worried about having too much timing too quick at the "wrong" spec of 5-7 BTDC and wasn't sure if it would "ping" or stumble on holeshot. I did read about the lean feature with those carbs and put the bb in.

Looks like I need to buy the proper manual but I will ask, I understand the function of the idle stabilizer to add (advance) about 9 deg of timing when rpm drops below 550 ....AND....it adds 6 deg's of timing just over 5600rpm and removes it as the rpm drops below 5400. Again, I do have it removed from the engine from what I learned in my searches here.

I really need some time out on the water to tweek and tune, read plugs, etc. My previous boat/motor I had for 11 years and knew it inside and out. This one I have known for 3 weeks and it's my first Merc. Seems like a good compact design compared to the V-4 I had before. Merc wiring is pretty terrible though.

Thanks for the correct #'s