evinrude powerhead compatibility 1980 25hp

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altrocker1

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so i have mixed information and i wanted to get a confirmation. i recently acquired a complete evinrude 25hp disassembled in a box minus the powerhead. i have been told that i need a 79-1980 powerhead from some folks, others have told me that i need a 1971-2001. any help would be appreciated. i've found several powerheads on ebay but most of them are listed for 1981 and up...
 
Chinewalker

Chinewalker

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Re: evinrude powerhead compatibility 1980 25hp

From 1979 to about 1982 or 3 the 31.5 cube 25hp used the earlier style lower unit with the exhaust exiting above the propeller. As such, it used a smaller diameter driveshaft and splines - with matching small splines in the end of the crankshaft. They eventually switched the 25hp over to the through-hub style lower unit used on the 35hp, and with it, the crankshaft got the larger splines in the end.

Because of this small spline arrangement, you cannot use the later 25 or 35 powerheads on your 1980 lower unit - unless you're up for swapping around crankshafts, etc. Find a powerhead with the small splines and you should be good to go.
 
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altrocker1

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Re: evinrude powerhead compatibility 1980 25hp

cool...just the info i needed. i will search for a 79-83 powerhead. the lower unit i have is in great shape. all i need is a prop and a powerhead and i should be back in business
 
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altrocker1

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Re: evinrude powerhead compatibility 1980 25hp

i just texted him...i hope he will ship it. if not, minneapolis is only 3 hours up the interstate from des moines
 
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altrocker1

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Re: evinrude powerhead compatibility 1980 25hp

well...the powerhead is on its way. i hope it works out...now i just need a service manual! anyone have a 1980 fsm they want to sell
 
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AlTn

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Re: evinrude powerhead compatibility 1980 25hp

try ebay, or ken cook co., iboats may have one as well
 
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altrocker1

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Re: evinrude powerhead compatibility 1980 25hp

finally got the powerhead this weekend...$85 shipped to my door. i took it over to the shop and crossed my fingers hoping the driveshaft was the right size and it fits perfectly...the powerhead looks great on the inside, no scoring or scuffing on the cylinder walls. i didn't open the crank case, but it sounds smooth when i turn it over by hand. going to order some gaskets and hopefully i can get to work on it when i get home from a work trip in 2 weeks!
 
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AlTn

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Re: evinrude powerhead compatibility 1980 25hp

sounds good
 
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altrocker1

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Re: evinrude powerhead compatibility 1980 25hp

jasper60103 said:
great!
Click to expand...

thanks for the tip sir...i got an evinrude shop manual on ebay for $30 so it looks like ill probably be doing a carb rebuild, a head gasket and a few other gaskets and it should be good to go. i will also be shopping around for a prop. i sort of forgot that it didnt have one, but that should be fairly easy to find.
 
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