exhaust manifold hoses

If it is a closed system, then it is completely different. For example, the intake manifold has an open rear coolant crossover.

 

replies

Thanks for the effort on the replies, though not sure I'm closer to an answer. This is a closed system. Expansion tank not radiator. Thermostat feeds tank, tank feeds down under boat to keel cooler, back to engine water pump. Water pump has two external feeds/ports, (one port, one starboard). Each exhaust manifold has two feeds/ports at foreward end. Intake has a port on each side forward end. Is it possible the water pump ports are taking water in to the block, from either the exhaust manifolds or intake rather than pushing it out as I envision?

 

So if you have a keel cooler then the exhaust manifolds should not be connected to the keel cooler at all in any way !!The keel cooler is to replace the radiator if it was in a car . Does it have a pressure cap ? need to use all the anti corrosive stuff you have in your car in the system!!
The pipe for the intake manifold should alsi be in this system as well not the raw water system the manifold needs to get warm to atomize the fuel better and warm up quicker . Should not be connected to the exhaust water in any way !!.

If the exhaust manifolds are in the keel cooler system you could end up with your motor over heating its self as the keel cooler will not be able to cope with all that extra heating the manifolds will produce !! not at slow speed but once the motor is working hard and the speed is getting up !!

The only reason for a raw water pump would be is for the oil coolers if it has any ! transmission oil and engine oil in that order and then the exhaust manifolds then into the exhaust pipes and out the back !!The exhaust pipes should have a gradual fall all the way to the transom and if the flanges are close to water level they should have flaps to close the end of the pipe when the motor is not running to prevent wash back up the pipe from a stern wave .

Any chance of posting some photos of the complete set up . We are all shooting in the dark without actually seeing whats there !!.

 

You can hook it up however you want but keep the motor warm and the head warmer. Oils can be cooled straight from the sea and do not suffer thermal shock. Exhaust last them dump it out the pipe.

 

raw water

This boat is set up with raw water coming in for the sole purpose of entering the exhaust "risers" which bolt up to the exhaust manifolds where it is then sent down the exhaust pipes out the stern thru baffles. The fresh water system has to cool the entire package; engine & exhaust manifolds. This set up has always run hotter than I'd like, which I attribute to the fact the boat was built with a 350 and keel cooler to match, before the 455 was put in 25 years ago. Keel cooler stayed the same. I will try to post some pictures soon. Oh, the transmission oil cooler is inthe keel loop also.

 

I think that there may be some confusion with the terminology. On a marine engine, the pump in front of the block is called a circulating pump. The water pump is the one that moves coolant through the heat exchanger.

 

I have set up a few engines like this. I have found it is best to supply the exhaust manifolds from the rear of the engine. You also need a bypass hole or opening in the thermostat housing to allow water into the manifolds before the thermostat opens. If your thermostat housing does not have a bypass opening, drill holes around the flange of the thermostat to allow coolant into the manifolds. Coolant inside the manifolds gets hot very quickly before the thermostat opens. It is also advisable to have a bleed cock or plug on top of the thermostat housing to bleed air off the top of the block.

 

Gonzo - the "circulating pump" is part of the freshwater loop...mounted on the engine over the timing cover. In my case, the circulating pump moves fresh water thru the engine AND the heat exchanger, (a keel cooler). The "water pump" using your terminology, provides raw seawater to the risers for the sole purpose of cooling the exhaust gases sent out the exhaust pipes.

Carteret - the exhaust manifolds are gasketed on the rear such that only exhaust gas passes to the risers, joining seawater from a Jabsco pump out the transom. Both ports for the exhaust manifolds are on the front end. I just don't remember which of those goes to/from the engine water pump (circulating pump) versus the intake manifold. It may not matter; just not sure.