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'73 Evinrude 135 High Speed Jets

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geezer1

Contributing Member
I ordered a set of high speed jets from marineengine.com for my '73 Evinrude 135. The old part # (318657) is unavailable & is replaced by #320502, so I ordered a set of #320502. The originals were size 73C, but the now available #320502 is 76C. Why did Evinrude go up in size, anyone here know? I'm sure there would be issues if I mixed these with my 73C's, right?
 
BTW... There is nothing addressing the change in size in the parts listing. I just happened to notice it when I checked them upon receiving them.
 
Can't say for sure in this particular engine, but OMC changed a lot of jetting because of the changes n available gasoline over the years. If I am not too far off, when built that motor called for PREMIUM LEADED gasoline. When they quit making the stuff, motors started destructing from pre-ignition and detonation. Jet changes were just one part of the various cures. Some motors required thicker head gaskets to lower compression, and timing changes. Sorry, I no longer have all the service bulletins that came out.
 
Interesting...That brings up other concerns I have about this motor. I believe I'm going to post another thread addressing all of them. Thanks for the response. Geezer.
 
geezer1 said:
I ordered a set of high speed jets from marineengine.com for my '73 Evinrude 135. The old part # (318657) is unavailable & is replaced by #320502, so I ordered a set of #320502. The originals were size 73C, but the now available #320502 is 76C. Why did Evinrude go up in size, anyone here know? I'm sure there would be issues if I mixed these with my 73C's, right?
Click to expand...

That's something i wasn't aware of (or forgot about), but at any rate that's a ID increase of 3 thousands (.073 to .076). Quite an increase I'm thinking as back when they first came into existence, we received a few new engines that we had to enlarge the various jets by .001 or .002 and sometimes even the .002 was too much.

As "fdrgator" states, perhaps the change was due to the original jets being too small resulting in preignition because of the lousy fuel we now have to put up with.

Curious as to why you were replacing those jets after so many years.
 
I actually didn't replace them. I ordered new ones because I misplaced them. Found them here in my office and installed them before the new ones arrived. Can't remember why I had them in the office (it's a geezer thing, I suppose). Curious about the up sized jets... Is there something I should watch for that might tell me I need larger jets?
 
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