73 1150 bad rectifier cause no spark condition?

rectifier test, clymer manual, indicates rectifier bad. Could this be cause of no spark, no start? Been through a bunch of troubleshooting and started to suspect coil, sparks only on switching key on/off. Would spring for a new rectifier if I thought this could be cause.

Thanks
B

Re: 73 1150 bad rectifier cause no spark condition?

Nope, a bad rectifier on a CDI-type ign cannot be the primary cause of no-spark. A bad rectifier would let the battery run down, and ultimately you'd lose spark due to low battery voltage. But since you're sparking with the key thing, I'd expect your battery still has plenty of power.

More likely the distributor trigger is bad. Unfortunately the trigger is embedded in the distributor body and you have to pull the dist. apart and replace the body. Ain't cheap, but the newer CDI-Electronics brand aftermarket replacements are quite reliable.

Note that you must have power to not only the red terminal on the Stbd side of the switchbox, but also the white wire (on the same side), with the ign in the "ON" position. So check for that with a meter, 'cause a bad/intermittant ign switch theoretically could cause the problem. But most common issue on these is a bad/failing trigger.

Here's a thread with testing/troubleshooting info for your motor's ignition:

http://forums.iboats.com/mercury-ma...ouble-1971-merc-135-a-598103.html#post4161270

HTH............ed

Re: 73 1150 bad rectifier cause no spark condition?

Thanks Ed. I'll test the trigger as you describe in the other thread. I do have good battery, and 12 v on switch box red and white-with ignition on. questioning coil though. It only sparks with the key to on/off, on/start, and back. Won't throw spark at cranking.

Best
Brian

Re: 73 1150 bad rectifier cause no spark condition?

Tested as described in your thread. good, detailed. Got a great spark from HV coil wire to ground. Seems to point to the trigger. Wondering, before I purchase, any advice on checking the cap, rotor, rotor button? The rotor shows some wear and hairline crack in housing that accepts the shaft. Just want to buy the right part the first time-they're all quite pricey.
Your instruction were great.

Best
Brian

Re: 73 1150 bad rectifier cause no spark condition?

Brian, usually you can clean up the cap and contacts. As long as it's not cracked/physically damaged/arc-marked, it should be OK. A good blast of carb cleaner will do a decent job of cleaning out old, gunky deposits. Check the carbon contact for free movement & damage, it's not a real $$$ part to replace. If you pull and twist at the same time, it'll usually come right out. Check the contact spring for damage as well.

The rotor is cast onto the shaft and is non-replaceable. Maybe post a pic of the crack, the only concern I would have is if the rotor's structural integrity was compromised, as any parts which "grenade" inside the distributor are gonna take out the new trigger.

A new rotor was over $460 when last available from Merc, but there aftermarket replacements available; some new and used rotors are listed on eBay but still over $200 for any new one. So, unless there's some "terminal" problem with the rotor, you should be able to clean it up and re-use.

There are 2 small ball bearings in the distributor, the lower bearing is commonly available, for some reason the top is NLA from Merc, and expensive. But if you have a bearing house nearby, all they need are the numbers off the bearing and they're easily matched-up. Or take the numbers and order online. Last time I needed some I took the bearing #'s down to the local NAPA store and they were able to order them.

Be sure you don't buy bearings made in China, they're of dubious quality. Name-brands such as BCA, NTN, Fafnir, SFK, Federal-Mogul, Timken, etc are all good ones. The upper bearing pries out of the dist, if you're very careful you can pry it out without damaging it. Use 2 small "tweaker" screwdrivers in the small holes and pry on the outer races, not the metal shields.

The lower bearing is held in by a snap ring which should always be replaced, as the ring will rust then break with age. Another thing to grenade the trigger! My old 1350 did it at a very inconvenient time, fortunately back in the 80's a used dist assy at the Outboard Boneyard was only $50. Not gonna see those prices again! Once the snap ring is removed, the bearing drives out from above. Always replace unless it feels perfect.

Just be very careful when taking the dist. apart, as things can be damaged if forced. With the dist. removed, you pry down the lock tabs holding the top and it unscrews. Then comes the aformentioned top bearing. After that, you'll be able to see the nut that holds the rotor into the housing.

The best way to undo the rotor securing nut is by using a small imact tool with 3/4" deep socket. Hold the rotor in a gloved hand (to avoid damage to hand and rotor!) and give the impact short bursts (normal, Right-Hand threads). The nut should break loose easily.

Here's a couple of reference auctions on eBay, so you'll get an idea of the parts involved:

CDI Electronics Mercury 4 6 Cylinder Distributor Rotor Shaft 994 4371 | eBay

Trigger Kit for Mercury 4 6 Cylinder CDI 134 3736 Replaces 393 3736 332 4177 | eBay

Here's a couple of parts diagrams for the distributor:

Mercury Marine 115 HP (6 CYL.) DISTRIBUTOR HOUSING AND ROTOR Parts

Mercury Marine 115 HP (6 CYL.) DISTRIBUTOR ADAPTOR AND VERTICAL LINKAGE Parts

Last but not least, the CDI-Electronics installation guide for the replacement trigger, has good instructions for disassembly of the distributor as well.

http://www.cdielectronics.com/wp-content/uploads/2013/01/134-3736.pdf

HTH...........ed

Re: 73 1150 bad rectifier cause no spark condition?

Thank you Ed. much detail appreciated. I'm going to pull the 'trigger' and go for it. I need this boat running and the wife gave authorization-wants me out of the house!

Will update periodically or with Q's.

thanks again,

Brian

Re: 73 1150 bad rectifier cause no spark condition?

Update. Trigger tested bad. Purchased Cdi trigger, arrived in one day from wulffe marine in mentor oh. Removed dist. installed new trigger into dist. Only came across two problems, had trouble determining if it an oversized spacer includeded in kit. Appears oversized is .010 thicker, tha original. Cruised into local steel mill, found somebody with a micrometer to measure. value of each were so close, I used the original spacer. Second, diagram wit trigger showed different order of wave washer, tab washer than I had originally. Also showed a Shim, not In my assembly. overall, instructions very good for disassembly, re-assembly of dist,with new Trigger. Have to bolt back on to motor, clean up and see if it fires.. Nuts are very tight quarters..

Re: 73 1150 bad rectifier cause no spark condition?

Oh, forgot about the condition of the original trigger. The snap ring was rusty and in multiple pieces and the 'pickup' had removed itself from its mounting on the housing. Could have something to do with it being bad, ha.

Re: 73 1150 bad rectifier cause no spark condition?

Engine fired. Running a bit rough. Trigger and housing don't seem to be in exact position as before. Have the timing and synchronizing procedure and will get to that. Should be in the water in a week.

Re: 73 1150 bad rectifier cause no spark condition?

Just to close out my thread, I've launched the boat, motor seems to be running just as always. Thought after the sync process-which I must admit I followed turboaddicts video, I'd have to make some adjustments. It doesn't appear I need to. Boat idled well, ran like I remember at full throttle, Id say 28 mph-30mph or so. Doesn't seem to be spitting at the pee hole like it should. its spitting at idle, more at bigger throttle, but seems to dribble a bit after full throttle. This is something I shouldn't have to worry about, as has new impeller and lower unit re-sealed with new shift shaft by local marine mechanic. I'll shove a wire up there to destroy any cobwebs and hope for the best. Thanks commander Ed for the troubleshooting guide identifying trigger as the culprit.

Re: 73 1150 bad rectifier cause no spark condition?

RE-inspect the water pump, the sides of the impeller have a small 'ring' that is raised and seals against the SS Cup and SS lower plate. Over time this wears a 'groove' in a circle around the center hole of both stainless parts. When this happens the impeller seal to those parts begins to fail and the pump no longer moves proper amount of water and has lower pressure.

This is dangerous for a stacked 6, if the upper part of the block does not remain totally filled it will overheat and seize #1 piston.

You can add a water pressure gauge and keep an eye on cooling pressure.

Re: 73 1150 bad rectifier cause no spark condition?

Thanks, I shoved a wire up the hole, freed up nicely. Spitting as it should, even better. I've seen the 'plug' in the head that I believe accepts the pressure guage. Is this something that you install and keep installed or just to check intermittently. I've noticed that the stud has some goo around it and have been reluctant to even mess with it. I'd be interested in getting a tach for it. My MerControl has the connector for one. If found one for sale on some auction site, would it be a simple plug it in and go affair, or bunch of wiring to do.
thanks,

Re: 73 1150 bad rectifier cause no spark condition?

A pressure gage is nice 'cause not only does it help you keep track of pressure while you're motoring down the lake or bay, but also long-term helps you judge the health of the cooling system. For example, if it's been running 10 psi (or 12 or whatever you end up with) all the time, and then slowly starts creeping down to a lower value, that's a very good sign that the impeller is wearing out or other issues need attention. The plug should come right out, if it's stuck you can apply heat from a propane or Mapp torch. It's a 1/8-NPT fitting, spread a thin coating of Permatex No. 3 or other suitable dressing on the threads before installing.

You can wire the tach directly into the connector plug on the remote control. Old-style tach harnesses can be hard to come by, but you should be able to just crimp a male "spade" connection on your wires and plug them in. Maybe run some electrical tape around the entire mess, to keep it in place.

Here's a wiring diagram for your motor:

http://www.maxrules.com/oldmercs/Wiring/1966ona/35.jpg

You'll note the wiring colors to that connector plug:

Black=Ground;
White=Switched +12V;
Brown=Tach Signal.

On older Mercs, the brown tach signal wire was connected to the switchbox (right next to the green coil wire), and a special tach was used.

The standard marine tachs available these days won't work when driven off the switchbox. However, if you move the brown wire on that side of the switchbox to the rectifier, it'll pick up signals from the 12-pole alternator and this is what a "modern" tach needs.

So, if your brown tach wire is still on the switchbox, move it to the rectifier, to either of the yellow stator leads. Definitely don't hook it to the +12V Red lead, that'd be bad! Doesn't matter which yellow stator lead you hook it to, either.

Found an auction on ebay for the tach harness you need: Mercruiser Mercury Tachometer Wire Harness w 3 Blade Plug Classic Tach | eBay

Lots of tachs on ebay or here at iboats.

If you spring for a water pressure gage, you'll want one with a 0-15 psi range for best accuracy, here's one I found on ebay:

Mercury Quicksilver Water Pressure Gauge 0 15PSI Part 825734 Brand New | eBay

HTH..........ed

Re: 73 1150 bad rectifier cause no spark condition?

Thanks Ed, wouldn' t be this far ahead without your very thorough posts pointing to trigger. Running great back on the water.
Very best,
Brian