Raw water hose routing for 1973 Ford 302 mercruiser 188 OSCO Center riser manifolds

The instruction sheet refers to a single hose system #CRRG and also a 3 hose system CRRG-FW. The factory hose system routed the water through engine water pump and out the thermostat housing through the log manifolds and out through the rear risers. The instruction does not show raw water through the engine water pump or the thermostat.

It only shows raw water going into the manifolds and out of the risers.

The gasket between the manifold and the riser for the CRRG 1 hose system has an extra hole that is not shown for the gasket for the 3 hose system.

Which hose system should I use? Single hose or 3 hose?

Single hose system shows raw water entering manifolds and discharges through the riser using the extra hole in the gasket.

3 hose system show water entering the manifold by hose and a hose from manifold into the riser.

Does raw water go into the engine from the outdrive through the eingine water pump, out through the thermostat, into the manifold and from the manifold by hose into the riser which would account for 2 hoses. If so I would not know where to put the 3rd hose.

Thanks

Does the raw water pump have two or four fittings? You should be able to find some flow charts and sort it out. The guys here can help do you have pics?

The "3 hose" system is for engine with heat exchanger; closed cooling. You haven't said what type of cooling system you have.

Agreed...... we need more information from you.

yellowbk said:

The instruction sheet refers to a single hose system #CRRG and also a 3 hose system CRRG-FW.
Please post a photo of this instruction sheet!

The factory hose system routed the water through engine water pump (engine circulating pump) and out the thermostat housing through the log manifolds and out through the rear risers. The instruction does not show raw water through the engine water pump or the thermostat.
Again...... we need to see this instruction sheet.

It only shows raw water going into the manifolds and out of the risers.
Are you looking at a schematic for the Log Style yet you are installing Osco Center-Rise manifolds????

Does raw water go into the engine from the outdrive through the eingine water pump, out through the thermostat, into the manifold and from the manifold by hose into the riser which would account for 2 hoses. If so I would not know where to put the 3rd hose.
Again....... are you trying to use a schematic for the old Log Style manifolds and Elbows while you are actually using Osco Center-Rise manifolds/elbows?
Your thread title implies "Osco Center Rise"!
If you are changing from the Log style manifolds w/ rear elbows to the Osco center-rise manifolds and elbows, I would completely re-plumb the system!
Look here at the array of schematics.
https://images.search.yahoo.com/yhs...&hsimp=yhs-pty_weather&type=we_appfocus340_cr



But again...... we need more info.
Is the engine Raw Water Cooled, or is it fitted with a Closed Cooling System?

Thanks

Click to expand...

the mercruiser 888 (ford 302) log manifolds have dedicated inlet and outlet hoses from the t-stat housing and a separate hose to feed the risers cuz there's a blockoff plate to isolate the manifold. if you are going to plumb up the new manifolds using the factory configuration, then you use the blocking gasket under the risers. this is a 'three hose' configuration.

if you are going to use the single hose (non-standard) configuration on an otherwise stock engine, you'll have to follow the 'directions provided'....which should state to use the gasket with the 'extra passage under the risers and somehow block off the fours hoses that would have passed the water to and from the log manifolds....

If the OP is going to use the Ocso center-rise exhaust system, and if he wants to simplify his system, he will also need a T-stat housing with twin outlets only.


He will do away with the log style plumbing altogether (although I understand why Merc did this for the Log style........, that plumbing is not necessary for the center-rise style).

He will go with a single seawater feed at the front of each manifold, and will plug the rear ports.
The seawater will then route through the manifolds, up/through the transfer ports, on to/through the Elbows and out into the exhaust flow.


I had to modify this image because I was not able to find a schematic that shows how this would be done.
It still shows the GM T-stat housing that would need to become a Ford Windsor style!
These manifolds are NOT Osco..... although the plumbing will be the same.
It also shows a restrictive transfer port gasket...... I would use a fully open transfer port gasket.






.

Thanks. I've attached more info. Thoughts?

This type of conversion (per Rick's post) is very doable. I successfully converted a circa 70s Chriscraft log manifold Raw water engine with "Thermocon" valving to OSCO center rise for a friend of mine using this setup.

Thanks everyone for your help!