Water Flow 1999 Mercruiser 5.7L

[kwoolard]

There is a hose that runs from the starboard exhaust manifold to the intake manifold on my engine that is not shown in any water flow diagrams that I have for my eninge. Hopefully the jpeg file attached to this post. You can see the hose on the manifold. It is a steel hose that has a black wrap around it. I am not sure what the purpose of this hose is. Also, I am looking at purchasing a half freshwater kit for my engine and would like to know also how I would need to reroute this hose for the kit since the intake manifold will have antifreeze running through it and the manifolds will have raw water running through them.

Thanks

 

[WillyBWright]

Re: Water Flow 1999 Mercruiser 5.7L

I had a guess, but I have no idea except that it doesn't involve coolant. 350 Mag, 5.7L carb 2- or 4-barrel, or 5.7 EFI?

Closed cooling or raw water?

Alpha or Bravo?

Pictured is TBI closed cooling Bravo?

 

[John_S]

Re: Water Flow 1999 Mercruiser 5.7L

It transfers heat from the exhaust manifold to the intake manifold to prevent carb icing and better drivability. On vortec heads there are not any exhaust crossovers, which are normally used to provide that heat.

 

[kwoolard]

Re: Water Flow 1999 Mercruiser 5.7L

That makes sense....the 302 ford I have has a crossover port. Does this line transfer the heat using the exhaust gases? It seems as if the line taps into the exhaust manifolds cooling jacket.

Also, are you saying that the heads I have are Vortec heads?

This is a 2 barrel generation II Alpha, raw water cooled.

Thanks

 

[kwoolard]

Re: Water Flow 1999 Mercruiser 5.7L

ooops....double clicked

 

[John_S]

Re: Water Flow 1999 Mercruiser 5.7L

As of '98 all merc 5.7L's 2brls were vortec head, rated at 250hp. Count your intake to head bolts to be sure. If you have eight, four per side, its vortec. If it has 12, it is standard head, and don't know why that pipe would be there.

 

[kwoolard]

Re: Water Flow 1999 Mercruiser 5.7L

It is Vortec heads....4 bolts per side. When converting to a half closed cooling system, does anything have to change with that crossover pipe? Also, where is the best place to get a closed cooling system?

 

[kwoolard]

Re: Water Flow 1999 Mercruiser 5.7L

I just wanted to revisit this as I couldn't get a clear answer as to how that exhust crossover works. The crossover line on my engine runs from the top of the exhaust manifold to the intake manifold. I am not familiar with the design of my particular exhaust manifolds but it looks like the crossover line taps into the water jacket. Or is it sealed from the water jacket and taps into the exhaust passage? Also, why is this exhaust crossover not mentioned in any of the service manuals for 5.7L's with Vortec Heads?

 

[Bt Doctur]

Re: Water Flow 1999 Mercruiser 5.7L

It taps into the exaust port to supply heat for the carb.