difference between 1970's & 1988 9.9 powerheads?

[boatster]

Hi I am trying to rebuild a 1988 Evinrude 9.9 motor. I want to replace the powerhead with a 1970s powerhead. Is the std bore and std pistons the same between these two generations? Or would I have to get specific pistons for the 1970's powerhead? I read in some aftermarket parts sheets that there are two differing designations for the pistons pre 1980 and 1980 on up. Anyone know what they're for?<br /><br />Thanks.

 

[boatster]

Re: difference between 1970's & 1988 9.9 powerheads?

bump. Anyone?

 

[Johnnielund]

Re: difference between 1970's & 1988 9.9 powerheads?

Boatster,<br />I'm 99% sure the 9.9 was toatally redesigned from the prop up in 1965, and then again in 1974. In 1974 they introduced the 15 HP and the 9.9 (detuned 15). From 1965 thru 1974 it was a 9.5. Previous to 1974 there was a 10 HP. Hope this information helps.

 

[Chinewalker]

Re: difference between 1970's & 1988 9.9 powerheads?

Okay, the earlier pistons (1974-1980 or so) can be fit into a newer block, and vice-versa IF you swap out the pressed-in needle bearing in the con-rod with it. The reason is the wrist pins in the pistons went to a larger diameter with the later 9.9/15 models, and rather than change the connecting rod, they changed the bearing within it. Replace them as a set - don't mix and match early with late, etc.<br /><br />- Scott

 

[boatster]

Re: difference between 1970's & 1988 9.9 powerheads?

Thanks Chinewalker. I will do accordingly. <br /><br />Boatster