TOPIC: Mercury 2005 50HP Won't Fire!

You all know how much I love egg beaters. They make great boat anchors for inboards! Anyway, I own one, a 2005 Mercury 50HP. It came with the pontoon boat my wife just had to have...but now she hates it...too slow. Women! In October, the engine ran fine, after I rebuilt both carburetors, replaced fuel lines, etc. Now, after sitting in storage for barely three months, it won't fire...zero spark. It turns over like crazy and it's not the ignition switch...I checked. I have a 3-pound lineman's hammer I call "The Big Hurt." I'm about ready to make some serious impact adjustments. Like I said, it's just been sitting in covered/locked storage. Any ideas what the problem could be?

Is the lanyard safety switch on?
What is the serial number of the Merc? (located on the starboard side of the swivel housing - aft of the transom)
doc

Yeah, Doc...the clip is in the safety switch. I'll have to go retrieve the serial number tomorrow. The boat is back in storage. I'll get back to you when I have it. Thanks!

We have same motor on Mom’s pontoon. One problem we had was that inside of squeeze ball deteriorated and tore which allowed a tiny piece of rubber get in the line preventing starting. Hooked up our separate portable tank off of fishing motor and it ran. First we thought it was water in tank or gas line. ... and for some reason her motor also struggled pulling through a water separator, so just run line directly. We cut that outer ball open to find the internal deterioration... ethanol problem maybe ate it up?? Just some thoughts. Good luck- we like our motor. They do make faster tri-toons with 2 or 3 300s that can go 100mph. Price tag rivals a fine Cris Craft!

Mark,
It sounds to me like your problem was ethanol related.
I've seen a bunch of the gray fuel hose that has an internal collapse problem with ethanol.
I don't think that is Jan's (Nautilus's) problem.
IF,...You can provide me with a serial number (since Jan isn't where his Merc is) I can do a search as to which ignition system his "might" have - if it is the same as yours.
IF,...Jan's ignition system is the later one with CDMs,...I'm over my head as to how to trouble-shoot it.
If his is still and ADI system,...I'll be able to help him.
doc

Doc, unfortunately the rig is stacked on a rack in a locked Marine storage building until early May so I am not of much help. Sorry guys.

OK...here's all the info on the engine. Sorry for the delay.

2005 Mercury, 50 HP, Model 50ELPTO, serial number 0T981538

It's not a fuel problem, It's spark...actually, no spark. Ignition switch checks out. The clip is in the kill switch. The engine has been sitting in covered storage for three months and it ran fine when parked.

I have never understood why an outboard motor is preferable to a direct drive inboard, aside from the fact that an inboard takes up a lot of deck space on a small boat. Outboards are problematic and they cost like hell! 2018 MERCURY Pro XS 175 hp. $11,295; 425 HP big block Chevy $7,500. I just don't get it.

Of course, the worst is a stern drive. Someone thought it was a good idea to design a system the makes two right angle turns, needs to swing side to side, needs to be raised, sits in the water constantly and leaks, collects crud...or both, and mounts through a giant hole in the transom.

I'll stick with a propeller in front of a rudder. OK...got that off my chest. I feel better now.

Well, outboards are light, give you more room in the hull, and are more easily changed-out for repower. Inboards are usually more economical but then you've got issues with the drive system always in the water, very problematic in salt. Personally I think the best powerplant for something like a tournament ski boat is an inboard, you just can't compare the power of a V8 with anything else and they're quite economical compared to a 2-stroke outboard, especially.

The other thing about 2-strokes at least, is that they put out a lot of power for their weight. I personally won't work on stern drives, but that's just me. They can be a compromise between inboard and outboard.

Your 50hp 2-stroke isn't extremely complicated, the most radical change they made on the later motors is with the ignition system. Instead of individual switch boxes and coils, they have gone to what is called a "CDM" Which may stand for "Capacitance Discharge Module" or something like that, I didn't find any good clarification on the acronym in an internet search.

At any rate, your engine has (3) of these CDMs. One per cylinder. They are a combination of coil and ignition module in one. You still have a stator, and a trigger assembly under the flywheel.

The stator windings could be bad. You can tell this with a resistance check, usually. The trigger usually has one segment per cylinder, so the whole thing would have to be burnt out in order to work. Not as likely to happen, typical trigger failure causes a loss of spark on one or a few.

These models suffer from broken flywheel magnets. They also complicate things by having a rev limiter that can fail. Obviously the mfrs have never heard of K.I.S.S. - - Keep It Simple Stupid!

Here are some of the electrical components on your engine:

CDMs: www.marineengine.com/parts/mercury_marine_parts/sn/0T981538/1050412DD/11493_30

Stator and Trigger: www.marineengine.com/parts/mercury_marine_parts/sn/0T981538/1050412DD/11493_40

One other thought, this is a typical ADI (Alternator Driven Ignition) system that is grounded to kill spark. So if there's a problem with the kill switch or shorted-out wiring somewhere, you'll have no spark. So one of the 1st troubleshooting steps is to disconnect the ign kill wire(s) at the motor and see if you regain spark. That's a black wire with yellow stripe.

I did find some info at CDI Electronic site on troubleshooting CDM ignitions.

It's easier to download the 50Meg file on a PC and view/print pages in Adobe; failing that, the online interface is clunk, but works. Online link is listed 1st.

www.cdielectronics.com/troubleshootingguide/

Info for your 3-cyl, 2-stroke 50hp is on pages 109 and 110 of the manual.

www.cdielectronics.com/wp-content/uploads/2016/12/7th-Edition-Troubleshooting-Guide_RS.pdf

I scanned-in the 2 pages and they are attached. There's quite a few things involved with the troubleshooting, so be sure to carefully follow the sequence outlined. Those CDMs can be a real Bugger!

I'd much rather work on the older models. The new ones are all fancy and such, but they use lots of plastic parts and it seems the mfrs have gone out of their way to make them even more complicated and hard to work on. They obviously don't want you to fix an old motor, just buy a new one!

HTH & G'luck.........ed

Jan, Ed had it. KISS. If as you say (the old "it ran before it was stored") is true I would suspect either moisture or rodent.
Mice have an affinity for insulated wires especially in tight spaces. Moisture could just corrode an easy to look at connection. Before spending a whole lot of $$ pull all the quick connects apart and clean and grease them up. Of course you've already done that. The starter turns so you're somewhat there. There are schematics available on the net that should draw a picture of where to look. I think you could eliminate the individual cylinder systems and look for a wire that would kill the main spark producing contacts.
My very first guess would be a bad ground somewhere.
www.bing.com/images/search?q=Mercury+Outboard+Wiring+Diagram&FORM=RESTAB

Thanks to all for the help. I haven't been able to sign onto this site for a few days...don't know why. Anyway, a belated thank you. It's rained like hell here for three days in a row and I haven't been able to fool with the motor. After I do some snooping and testing, I'll let you know what I find out...if anything.

Yeah, we were down for days. Glad to see the site up-and-running again. You must be the first one back on the site beside the Mods, Congrats. Maybe you'll get a rain-break soon. Beautiful up here in W. Wa, sunny but a bit chilly at night (high 20's for a few days). Then it'll warm up a bit and rain some more, probably. At least my last power bill went down, guess we're rolling slowly towards Spring!

Keep us posted, haven't played with CDM's yet so it'll be a learning experience for many of us, I'd expect.............ed