1985 350 Mercruiser engine replacement with a 1987 350 Mercruiser engine- Need Assistance

[Seas the Day II]

I have a 1985 25' Sea Ray Sundancer with a 350 Mercruiser engine with a blown head gasket. I also have a 1987 350 Mercruiser engine I took out of a 1987 20' Imperial V202. My concern is the different engine years. The rubber boots from the risers to the elbows on the '87 engine are 4". The rubber boots on the 1985 engine are 3". Will I also have to change the Y pipe? Were there any other modifications I should be aware of? Any assistance is greatly appreciated.

 

[kghost]

Direct replacement except the coupler but I believe all the newer coupler are the same for even older motors.

The only difference between the two motors is the '85 is two piece rear main seal, the '87 is a one piece rear main seal.
Valve covers are different and maybe the intake manifold bolt pattern

other than that a direct replacement.

The difference in exhaust boots may be for a different manifold diameter output and I would go with the larger ones if it were me but if you cant use the smaller ones no big deal so if you have both with all the different parts use what is needed to make it work..

I don't believe the "rams Horn" (Y pipe) is any different but if it is swap the two.......