Stator winding query on Mariner 1989 115 hp 6 cyl

"My Mariner 1989 6-cyl engine after running almost flawlessly for years suddenly started missing and lost half its power. It starts just fine, seems to idle just fine, tested all the cylinders for spark - all ok, but just wont get going. As you pull away, sounds like its going to go, but then backs off and misses horribly...on off on off, and can bearly get onto the plane.
I have the mariner manual and have tested the trigger coil - all fine. Barring all other possibilities, i tested the stator coils. Both blue coils test fine and perfectly within limits. Now the recommended ohms for the red leads to ground are 90-200 ohms. The one is 145ohms the other is 60 ohms. This is 30 ohms less than 90 ohms. Would or could this be such a major contributor to my problem? Is this THE problem or could it be something else? The engine wont need tuning or wont have timing issues, it is so perfectly tuned i dont want to tamper with that. It was a sudden change while on the water the other day. Almost like something broke. I havnt tested the rectifier yet, as it seems this can also cause poor running if blown. The wires upon close inspection were perished and might have been touching the motor ground - hence my suspicion.

Thanks
Ryan"

"Ryan, your test results expla

"Ryan, your test results explain your issues perfectly.

Although the stator appears as a single unit, it is actually 3 independant components that are just grouped together.

You have charge coils which provide power to ultimately recharge the battery and you have ignition coils.

The ignition coils (or windings or bobbins) are further divided into 2 separate components.

The low speed windings (blue leads) which provide power to the ignition at "all" rpms and the high speed windings (red leads) which supplement the ignition power at higher rpms (usually above 1500-1800 rpms roughly).

If you are getting "out of spec" readings from the high speed windings, then your stator is not producing enough power at higher rpms to run the ignition properly.

That totally explains the missing or loss of power.

Unfortunately, the entire stator must be replaced to correct the single problem with the high speed section.

How did it happen? You note a possible issue with the rectifier wires. If the charge coils can not (shunt) the power they generate ultimately to either ground or a battery, the power will (back up) and burn something out.

You could have had a fault in the charge system which took out one of your high speed bobbins.

That is actually a somewhat common cause of stator failure on Mercs...."

"Hi Graham. Thanks for the res

"Hi Graham. Thanks for the response. Just to add to the issue.
On some sites i have read that the high-speed coil resistance should be 90-200 ohms, and other sites recommend 60-150 ohms. This latter range is well within spec of mine being 60 and 143 respectivly for the 2 high speed coils, however falls outside the tolerance range for the 90-200ohm. Anyway advice on this?
The engine is quite old as you can can well understand, although its in really great condition. It still looks new all round, but there are several wires which have perished for some reason. The yellow wires (charging) from the stator have perished badly, and about 40mm before they connect to the rectifier i noticed they were touching the body of the motor on a plate edge. Whether there was any contact or not i can only guess, but looking at the edge it looks as if there might have been some electrical contact.
Funny enough the green wires with the white stripes from both switch boxes to the ignition coils were perished and breaking up too. Ive since remedied with insulation tape, although this is of course a patch job.
I also insulated the charging yellow wires but its not easy to do this far back enough as the wires dissappear into and under the flywheel in a sleeve so i could only patch up what i could physically see.

3 more tests i would like to run just to make 100 cement sure are as follows;
1. dissconnect rectifier and see if miss goes away
2. test voltage outputs from the stators coils while its running (the 25Volts and 180V) and finally
3. Test that the fuel flow into the engine from the pump is steady - should be a first test, but ive had hunch its electrical from the start - by the sudden step change in performance.

Ive already changed spark plugs and visually checked for spark on all cylinders which was all fine. Of course higher rev sparks checking will be a bit tougher so waiting for my dad to return from holiday to assist.

Thanks"

"The resistance tests are usua

"The resistance tests are usually the first step to further testing.

If the ohms are out of spec for an ignition part (such as the stator or trigger), that would warrant further tests for voltage, as you have noted.

Voltage tests must be performed with either a DVA meter or a standard volt meter with a DVA adapter.

The stator produces AC voltage, but the ignition runs on DC.

The voltage specs take that into account, so you are looking for specific voltages that have been converted or normalized (how ever you want to look at it), and a "normal" volt meter will not give you the reading you are looking for.

A Direct Voltage Adapter (converts in the same manner a CDI or Switchbox would) the AC from the stator so that a volt meter set to read DC will get an accurate reading.

So even if you do not have the necessary equipment at home (most don't), any outboard or motorcycle shop should be able to check the output (for a small fee of course).

IF you disconnect the rectifier to test, make sure you ground both the yellow leads to the engine block before starting the motor. The power generated by the charge coils has to go somewhere.

You can simply find two bolts or screws on the powerhead (in different locations), back them out a bit and secure the leads. Alternately, if you have a marine dealer close by you can pick up and "isolation block" for a couple of bucks - it's just a little two screw tab "thingy" that screws into the block (always lots of spare tapped holes in the block) and then connect up the two yellow wires - it isolates the two feeds and grounds them out safely."

"One other comment - you call

"One other comment - you call you motor "old" - it's just an 89.

My "youngest" motor is a 90 and is little sister to a pair of 87's and a pair of 86's.

And I don't even consider my 1986 models "old" since they contain the same components that were used up until 2005 when most 2 stroke designs were discontinued.

A 1989 model is "just getting broken in" and I suspect it will outlast a 4 stroke of the same horsepower that is just coming off the assembly line today.

In fact, your particular configuration stayed in production as the 135 Merc until just a year or two ago - so "partswise" it is still a very "modern" engine.

After 2005 Merc continued to produce 3, 2 stroke models. The 135, 90 and 50 horse. The 90 and 50 are still produced for sales outside the US. The 135 was phased out in 07 or 08, but is still totally supported.

Your 150 uses the same block, ignition system and most components as the 135 making it a very desireable motor to own..."

"I have a 115 merc 84 model, h

"I have a 115 merc 84 model, had the same problem.I repaired the yellow wires,this only made it run rough. The thing is the wires are rotten all the way into the windings. I got a new stator now all is well.{sun}"

"Hi all.

Problem found - n

"Hi all.

Problem found - not solved yet. My dad came back from vacation and we set out to do some voltage tests, a rectifier test and a fuel flow test.
We started with driving the boat, opening up the throttle fully to hear what the problem sounded like. Still battline! So, switched off, then disconnected one of the yellow wires to the rectifier. (mind you, we didnt connect the wires to the motor casing, as i figured being a few amp output, shorting it would just cause a dead short in the winding, possibly blowing it up, so coundt understand that issue) Anyway, leaving it loose on 1 yellow wire, started the engine and WOW - shes back. 100%. All in all 5 minutes on the water and we were ready for a good 2 hours of tests. Ran her full taps for a few minutes, and we flew around the dam like a formula 1 car. Reconnected the single yellow wire to rectifier, just to make sure...back to square 1. So its confirmed. When the rectifier is connected, the motor just wont go, so, im assuming the rectifier is shot. Will take it off and see if we can get a replacement.
Otherwise, A-OK.
Thanks for the assistance guys. PS: i think we were both amazed at how a blown rectifier can affect the engines performance so severly.

Thanks again."

Hey Guys, I have a 1984 Mariner 150 and I tested the coils and it has fire on 1-3-and 5 but no fire on 2-4 and 6. Does this sound like the stator....

you should have to coil modules for bank 1 and bank 2. swap those and check if you have spark at 4 5 6. if so then thats your problem.

Stator or switchbox problem, swap the red/blue wires around on pack problem follows its stator