Powerhead match

[Bitmess]

I have a 1975 Mercury 500 50hp and found a used powerhead at a reasonable price. He says the compression is 105 in all four. Does that sound a little low?
My serial number is 3821XXX and the other power head is a 1979 with serial number 4965134. From what I see in parts list his powerhead is a match for mine but I would like to make sure. Does anyone know for sure?

 

[Laddies]

Re: Powerhead match

Your power head is a belt driven ign. and the other is ADI the only way they would interchange is with the ign and other componets included yours is a long crank and his is a short crank.

 

[Bitmess]

Re: Powerhead match

Thanks for info!