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15/9.9hp connecting rod compatbility.

M

mrburls

New member
I purchased a rebuild kit for my 1976 15hp Evinrude (15604A), and it looks like the WSM pistons have a larger wrist pin (.55" instead of .50"), and the kit came with 22 needle bearings instead of the roller cage bearing.
My question is the following:
Can I use these new pistons with the same connecting rods? The bearings all fit nicely, looks like I would just need the thrust washers to keep them in place.
Or am I better of getting WSM pistons with 1/2" wrist pin and roller cage bearing because perhaps the connecting rods changed.

Thanks!
 
Myself I would install a newer set of rods.----I would not use loose needles in the early rods.
 
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Crankshaft is the same journal for many years.----Easy to look up here on this site.----Same journal bearing for all years.
 
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racerone said:
Crankshaft is the same journal for many years.----Easy to look up here on this site.----Same journal bearing for all years.
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Thanks! I was able to get a newer set of con rods and purchased wrist pin washers. Do they really just sit loose in there with the washer on both sides? Maybe its not that big of deal since these just would be a rocking motion anyway.
 
You can use the WSM pistons with the larger .55" wrist pins on your 1976 15hp Evinrude connecting rods if the needle bearings fit properly and you install the correct thrust washers to keep them in place, but you need to be cautious because the original roller cage bearings were designed for the 1/2" wrist pins, and using different bearings can change how the rod pivots and handles load; if you want to maintain the original performance and longevity of the rods and bearings, it might be safer to get WSM pistons that match the original 1/2" wrist pin and roller cage bearing, since the connecting rods may have subtle differences that affect wear and reliability.
 
zjacker said:
You can use the WSM pistons with the larger .55" wrist pins on your 1976 15hp Evinrude connecting rods if the needle roller bearings fit properly and you install the correct thrust washers to keep them in place, but you need to be cautious because the original roller cage bearings were designed for the 1/2" wrist pins, and using different bearings can change how the rod pivots and handles load; if you want to maintain the original performance and longevity of the rods and bearings, it might be safer to get WSM pistons that match the original 1/2" wrist pin and roller cage bearing, since the connecting rods may have subtle differences that affect wear and reliability.
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While you may be able to use the WSM pistons with the larger .55" wrist pins on your 1976 15hp Evinrude if the needle bearings fit smoothly and the correct thrust washers are installed to control side play, it’s important to be cautious because the engine was originally designed for a 1/2" wrist pin with a roller cage, and switching to a different Ball Screw Support Bearings arrangement can slightly change how the load is distributed through the connecting rods and bearings; for the best reliability and to keep the original geometry and wear characteristics, many people prefer using pistons that match the factory 1/2" wrist pin and roller cage bearing setup.
 
There were failures with the small pins , the factory made improvements.---I would never assemble 15 hp with the small pins !!
 
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