4.3 exhaust manifold

[feener]

hi any help would be great i have an 84 thundercraft with 4.3 i bought new manifolds pn# 51220 which replaces 99746a17 the ones off my engine are 99745 the new ones will not fit on. for the pass side to fit i put washers in to raise the engine up off the tilt/trim pumps which are the motor mounts but on the other side this will not work the hole at the bottom of the manifold for the elbow and drain are right on top of the pump on that side. any one come across this before.

 

[bruceb58]

Re: 4.3 exhaust manifold

Not sure if I read this right but if you are actually raising the engine, you can't do that without affecting the engine drive alignment. If this is the case, you are going to have even bigger problems when you wipe out your coupler and have to remove your engine.

 

[Howard Sterndrive]

Re: 4.3 exhaust manifold

tilt/trim pumps which are the motor mounts

no clue given as to what you are working on, but sounds like you are trying to put Mercruiser manifolds on an OMC 800 series stringer mount drive system.

The only modern available center riser manifolds that will clear those trim cylinders (not pumps) are the OSCO 99745 ones.
If that's what your old ones were, you should buy the same ones.

in related news, the 4.3 was first manufactured in 1985 so if you do have a 4.3 in your boat (and not a 3.8), you have some sort of real Heinz57 vessel there. Probably have a 3.8 Chevrolet.
I'm not sure the 99745's will clear the 4.3 valve covers. They clear the 3.8 valve covers ok.

 

[bruceb58]

Re: 4.3 exhaust manifold

There I go assuming what he had. I should know better.

 

[feener]

Re: 4.3 exhaust manifold

it must be a 1985 thank you you answered my question osco it is than

ty

 

[Howard Sterndrive]

Re: 4.3 exhaust manifold

The 1985 4.3's were painted silver. drive and engine silver.