power head swap 70 hp evinrude

J JACKSON

Petty Officer 2nd Class
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Apr 7, 2008
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180
will the power head off a 1978 70hp fit 1988 i found a great deal on one if it will fit my engine
 

pckeen

Commander
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Jun 20, 2012
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2,067
Re: power head swap 70 hp evinrude

Check the parts diagrams on marineengine.com

The powerheads look substantially different.
 

Bosunsmate

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Apr 7, 2012
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6,129
Re: power head swap 70 hp evinrude

As above. Check the base plates gaskets. If they arent the same then its time to stop as they would have a different base plate face so the inputs and outputs from the gearcase wont line up
 

J JACKSON

Petty Officer 2nd Class
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Apr 7, 2008
Messages
180
Re: power head swap 70 hp evinrude

ok if the power head i different will the foot on the 88 fit the 78?
 

Faztbullet

Supreme Mariner
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Mar 2, 2008
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15,589
Re: power head swap 70 hp evinrude

It will fit but you will need to use the complete 78 powerhead(ignition/carbs/linkages) and adapter plate as the 78 uses 5/16 dia. power head bolts and the 88 use 3/8 dia. Your also going to loose some performance as the 88 is a 56.1 ci and the 78 is the small 49 ci motor. Nothing will moun
 
Last edited:

bonz_d

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Apr 22, 2008
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5,274
Re: power head swap 70 hp evinrude

Also the 1988 uses a 4 spline driveshaft. The pre 1984 uses a multi spline
 

Chinewalker

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Aug 19, 2001
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8,902
Re: power head swap 70 hp evinrude

Also the 1988 uses a 4 spline driveshaft. The pre 1984 uses a multi spline

No, the fine spline didn't come into use until 1989. 1988 still used the 4-spline shaft. 1978 would be 4-spline. The 1978 and 1988 gearcases should interchange with minimal modification.
 

bonz_d

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Apr 22, 2008
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5,274
Re: power head swap 70 hp evinrude

Could have swore that while looking for a replacement crank for my 1988 70hp that what I stated is what I'd found. Now I can't find those notes. Dag nab it.
 

J JACKSON

Petty Officer 2nd Class
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Apr 7, 2008
Messages
180
Re: power head swap 70 hp evinrude

cool thanks for the help I am gonna go check out the 78 model Sunday if it is good i buy it and let you know how it works out, and i really don't think I will see much performance loss on a barge that might get 15 mph. All i really want to do is get back out on the lake
 

J JACKSON

Petty Officer 2nd Class
Joined
Apr 7, 2008
Messages
180
Re: power head swap 70 hp evinrude

well drove 2 hours to see a dang locked up motor, the guy said well it ran when i parked it. I guess i will be rebuilding the motor i have, everything i look at is either worn out or cost way more than me rebuilding mine will cost.
 
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