Chrysler 318 Manifold temperatures

[Svend]

Chrysler 318 Manifold temperatures

I was talking to guy last night that has been around boats all his life and he said a good thing to keep track of is manifold temperature vs the black temperature using one of those laser temperature devices...

Have any of you guys done this? What are the temp differences between block and manifold ?

He said the manifolds rust inside and reduce water flow...

Thought this was one of the bigger issues to watch out for...

Thanks

Svend

[larryeddington]

I have done that on both Crusader and Chrysler 318s.

In my case block was around 145 to 150 and manifolds around 120ish, you could hold your hand on them. The blocks in either type have a 140 degree thermostat if raw water cooled and higher for fresh water cooled. In either case the cool raw water flows through the manifold jacket then joins the exhaust on exit which cools the exhaust gas.

If the exhaust manifolds are too hot it is either stopped up or possibly exhaust gas leaking into water jacket. IMO.

[K4282]

I did this to diagnose my bad manifolds, hes correct, my laser temp gun from Ryobi was a great $25 investment. When I bought new manifolds and risors it was suggested to me by the dealer to take readings after installing them and again in a few years to start to monitor build up down the road as they age

[Svend]

great feedback!! thanks

I guess it is safe to say if the manifold temperature reaches the block temp, things are not good.
can they be cleaned out, descaled inside or better just to buy new ones...

thanks... this forum is the best!

Svend

[K4282]

ive heard of people cleaning them with some acid or something, i personally wouldn't bother, my feeling is what if they let go and you hydrolock the motor? for $1,000 I for manifolds, copper tubes, bolts, gaskets, elbows and risores shipped to me, well worth it IMO