OMC 250 (chevy 350) cooling System

Does anyone have a diagram or can you post pictures on the entire cooling system set up for an OMC 250(Chevy 350)Reverse rotation motor. I need to verify that I have the manifolds and the rest of the cooling system plumbed correctly. I will include a picture of mine and hopefully someone can post theirs and I can compare.

I overheated pretty bad today on the lake and I want to try to fix the problem.

Also the 2 grommets that are on the valve covers have 90 degree elbows on them, is this supposed to be the PCV valve and just a 90. You can see both of mine are blowing in to nothing.

OK let me see if I can explain this, the two hoses that are going in to the elbows on the risers is coming from the water pump. They are not connected that way now nor were they yesterday. Right now they go in to the top tubes on the thermostat housing.

it would be interesting to know why does it need all those hoses?

Ok so I just took off the valve cover on the right side in the picture and found three loose valves. Anyone have a procedure for adjusting these? Pictures of the water pump are on the way.

Ok here are some questions I need answered before I can continue.

1. Water comes in to the make up pump from the bottom of the boat then goes to the trans cooler then where. Right now it is going to the top of the motor via a T-connector.

2. On the risers, the two hoses coming out are anti-syphon valves, do I need these. I have seen nothing on here about them but on the Osco website it says the risers are equipped for anti-syphon valves and points to those two holes.

3. The water is supposed to go to the manifolds then on to the motor correct? The manifolds are supposed to heat the water up a bit before it hits the engine? If this is the case and I remove the hoses from the anti-syphon valves and get plugs for them then which hole on the manifolds does my raw water from the impeller go in to and where does the output of the manifolds go on the engine.

I am gonna lick this and get my boat back in the water next weekend.

Josh

Well took the thermostat housing off and what do you know, there isn't one in there. This boat is killing me. I can't figure out the cooling thing. I have five hoses that go in to where the thermostat is supposed to be, that's 3 more than everyone else. I know that I am not supposed to be pumping water straight to the engine from the river but that seems to be what I am doing right now. No one has these odd ball manifolds and risers from osco.

After looking at your pictures, and scouring the 'net for any kind of diagram I have come to the conclusion it looks like mechanic #2 has hooked up your cooling plumbing correctly.

From what I found on various internet forums, it looks like your manifolds are set up to allow for a fresh water cooling system to be optionally installed.

From what I can tell from the last picture of your plumbing the water does the follwing:

1. gets sucked through the pickup on the bottom of the boat.
2. goes through the trans cooler
3. goes into the RWP. RWP output goes back under the engine.
4. hose from RWP output goes to a T-fitting and connects to the top/front of the thermostat housing
5. Water flows into the block through the circulation pump. Once the block fills excess water will flow out of the t'stat housing through the back pair of hoses into the "bottom" of the exhaust manifolds.
6. water comes out of the exhaust manifolds at the top of the pyramid
7. water is injected into the exhaust stream through the anti syphon valves in the risers.

I found a plumbing diagram, that looks somewhat kinda sorta close to what you have. It's for a freshwater cooled setup. You'll just have to mentally block out the heat exchanger...
Sorry I can't be any more help. The one thing that's pretty straightforward on my PCM Ford is the cooling system plumbing.


The diagram...confuse yourself at your own risk!

how long did you ran the boat before it overheated?

It seems the plumbing is OK... just a bad impeller after so many cranks without water.

If not you can feed the thing with water, turn it on and try checking out each hose at a time so you can follow the water stream.

Luciano,
Did my description seem correct?

Thx,
Anthony

How about this:

Water from RWP to bottom of pyramid
Water from top of pyramid to top of t'stat housing
Water from back/bottom of T'stat housing to anti-syphon valves.

Incoming water needs to go to the front/top. Otherwise it will be dumping on top of the thermostat, which when open will have the RWP battling with the circulation pump.

I opened it thinking maybe I had a bad T-Stat, turns out there wasn't one in there. I would like to eliminate some of the hoses too but what I cannot figure out is why I have 4 hose inlets going to the top of the t-stat housing.

Aren't the manifolds supposed to warm the water going in to the t-stat housing.

Isn't the top connections on the t-stat housing basically an overflow that can be routed out the anti-syphon valve.

Shouldn't the anti-syphon portion keep positive suction on the top portion of the t-stat housing?

Tomorrow after work I will try to follow the water path and hook it all up. Once I get the t-stat in the boat will start right up as long as I am feeding it hose water.

Honestly, call Discount Inboard Marine on Monday. They will probably be able to give you a better answer about your cooling system.

Once I get the t-stat in tomorrow I am gonna be ready to test. I should have no problems if I hook the garden hose up to the outlet hose of the impeller housing.

I don't think hooking the water supply up to the top connections is the best idea as there are only two little holes in there to allow water through.

The mechanic did say he ran it for a while on the hose while they were tuning it. With it on the hose the impeller wouldn't have mattered cause there was constant pressure. He said it was cooling fine. I will leave it the way he had it only with a 160 degree t-stat installed and run it on the hose for a while at idle. If the t-stat opens up and the motor cools then it should be good to go once I get the impeller in the mail. I really do appreciate all the help you guys are giving me. I spent a lot of money at the mechanic and really the only way this boat is gonna run now is with me fixing it with the help of guys like you.