Sierra coils – Dimensional issues??

[nj-boatbuilder57]

Me again….same engine (’57 Johnson Javelin / 59 Gale Sovereign mashup).

Got it running….new OMC fuel pump (you may remember that my eBay cheapo pump fell victim to ethanol)…all is great. Except:

I can hear what sounds like mechanical knocking in the powerhead. Well, that’s not good….and I’ve come too far to find out I have a bad powerhead. Kinda bumming out, ya know?

Anyway, for reasons semi-unrelated, I remove the little door on the flywheel’s timing window, and I manually turned over the engine (plugs removed for reduced resistance). And I found the knock! The magnet lobes on the flywheel are scraping up against one of my coils. Every time the engine comes around, *smack*.

So for the umpteenth time, I’ve pulled the flywheel. I’m getting pretty proficient at it, too! 🙂

With the flywheel off, I can see the strike marks on one of the coils. Trouble is, these coils are as far "in" as they can go. The screws & holes are making hard contact; these coils are NOT going any further inward. To my fingernail, they are right exactly "on" the little alignment feet on the magneto plate, but they need to maybe go in a smidge more. But that’s not happening. For whatever it’s worth, these were put on with a ring. And, yes, that ring was hard to get off.

So here’s my question: Has anyone experienced dimensional issues with Sierra coils? These are Sierra 18-5181 coils. I believe Sierra has a pretty good reputation, but is this another case where "genuine OEM parts" are the guaranteed way to go? Should I just pitch these and put on genuine johnnyrudeOMCBRP?

Or…..if I were to remove the coils and make the screw holes just a wee bit enlarged, I could gain a few thousands (and I don’t need much……about 0.010 would do). Is that a possible solution?

Thoughts?

[jerry-ahrens]

Yes, the current Sierra coils are not good. The laminates, as you have described, are not manufactured very well, and are near impossible to adjust properly, even with the locating ring. BRP coils will solve the problem, but there are some other aftermarket coils out there that work. Others will chime in on this shortly. Or, save your original laminates, and install the coil onto them. The actual coil itself is fine, it’s the mis machined laminates that are the problem

[david-bartlett]

The right thing would be BRP Parts, but enlarging the hole a bit should work fine.

[garry-in-michigan]

The latest Chinese copy of the Japanese imitation of the German coil has an incorrect radius on the laminations. When pushed against the locating ring they leave noticeable gaps. . . 😀

[Buccaneer]

I had a little Evinrude that had a crankshaft that was slightly
bent, and caused similar problems. Hopefully it’s just
your Sierra laminates.

Prepare to be boarded!

[nj-boatbuilder57]

Interesting. Maybe I’ll put a runout gauge on the flywheel to see if there’s any wobble on the shaft.

But I suspect, as has been confirmed here, the Sierra coils are the issue. And if the radius on the ends of the lams are wrong, moving these inboard a tad (by enlarging the holes) seems like a non-solution.

Looks like I need to get some OMC coils on order!

[Bob Wight]

I once had the same problem with a Sierra coil that came on one of my motors. As David noted, you can just drill out the mount hole a bit but that’s a crappy fix IMO. The Sierra coils and other "unbranded" aftermarket coils seem to have the same problem with regard to fitment, so just best to use OEM coils.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[nj-boatbuilder57]

The money I "saved" by buying all of these cheap parts is really starting to add up! I’ve learned my lesson well, I assure you!

Two new OMC coils are now on order.

[Bob Wight]

BTW – my comment about drilling out the mount hole being a crappy fix wasn’t intended to diss on David’s note. That solution can certainly work but just seems like aftermarket coils are usually troublesome to fit correctly,

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[Tubs]

quote NJ-boatbuilder57:

The money I “saved” by buying all of these cheap parts is really starting to add up! I’ve learned my lesson well, I assure you!

You can usually save money by buying the best you can get.
That doesn’t always mean the most expensive.
There are a couple other options.
Put the new coils on the old laminates.
Or you just file down the laminates where they are hitting.

A "Boathouse Repair" is one that done without having tools or the skills to do it properly.

[Author]

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