1991 Johnson 70hp - powerhead replacement

[androsmj]

Will the powerhead from a 1984 Johnson 70 hp act as a substitute for a 1991 Johnson 70 hp?Thanks,Mike

[Dhadley]

Be very careful with that. This is the odd case where two powerheads have the same mounting bolt pattern but dont interchange. The 84 is a 49 cid and the 91 is the 56 cid model. The water inlet and exhaust are swapped. Its possible to mix them up, turn on the flushette and fill it with water.

[DHPMARINE]

Wow,that streches the imagination.First step is to look at the powerhead base gaskets,and driveshafts to see if they are the same.Then continue.My guess is the shift rod won't be compatable.Some shops cut off the shift rods,and weld what they need.I won't at my shop.DHP

[Dhadley]

The bolt pattern is the same but the base gaskets are not. Some do indeed have the same driveshaft splines.Be very careful.

[androsmj]

Thanks for the info. Is 1990 the first year they started using the 56 cid?

[Dhadley]

No, 1986. They used both for several years in differant hp models.