Help understanding OMC cooling system - Control Box

Hibbitz

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Jul 12, 2012
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I purchased a 1973 Slickcraft at the end of the summer and in addition to rebuilding the floor I am looking to do whatever maintenance and upgrades are needed for the engine.

The engine was originally a JX 245 which was essentially a chevy 307 that was mated to a Jacuzzi jet drive. I know the block is now a rebuilt 350 but I am not sure what else is original. It still retains a number of things like the valve covers, Q Jet carb, but beyond that I am not sure.

So...... to my question.:D

I am trying to figure out the raw water cooling system on this engine. Understanding that the system is fed by a hose that comes from the jet drive, I am not sure what the box is and what controls it? I'll need to double check the number of wires coming out of it but it looks like one has a boot/cover like it might go over a temp sensor.

Any assistance or information on these systems (specifically the control box) would be greatly appreciated.

Cooling_Control_Box.jpg
 

Levinz11

Senior Chief Petty Officer
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Apr 1, 2012
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Re: Help understanding OMC cooling system - Control Box

That "box" is the thermostat housing. The wires could be for: temp gauge, temp warning alarm, etc. It is not externally controlled. The thermostat inside opens and closes as the spring contracts or expands. Just like your car.
 

Hibbitz

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Re: Help understanding OMC cooling system - Control Box

Ok, thanks for the reply. I wasn't sure if there was an electric valve inside that would regulate/divert the water flow based on power from one of the wires which could be wired to the temp sensor or something.

I'll see what other info I can find on the "box" and determine what those wires are but it is good to know it doesn't effect the opening of the thermostat.
 

Don S

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Re: Help understanding OMC cooling system - Control Box

Could also be a voltage regulator. Item 77 below.

Volt reg.jpg
 

Bondo

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Re: Help understanding OMC cooling system - Control Box

I purchased a 1973 Slickcraft at the end of the summer and in addition to rebuilding the floor I am looking to do whatever maintenance and upgrades are needed for the engine.

The engine was originally a JX 245 which was essentially a chevy 307 that was mated to a Jacuzzi jet drive. I know the block is now a rebuilt 350 but I am not sure what else is original. It still retains a number of things like the valve covers, Q Jet carb, but beyond that I am not sure.

So...... to my question.:D

I am trying to figure out the raw water cooling system on this engine. Understanding that the system is fed by a hose that comes from the jet drive, I am not sure what the box is and what controls it? I'll need to double check the number of wires coming out of it but it looks like one has a boot/cover like it might go over a temp sensor.

Any assistance or information on these systems (specifically the control box) would be greatly appreciated.

Cooling_Control_Box.jpg

Ayuh,... Welcome Aboard,.... Strange lookin' exhaust manifolds,...

What's it say on the side of 'em,..??
 

bruceb58

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30,454
Re: Help understanding OMC cooling system - Control Box

That distributer is an automotive one. You need to replace with a marine one. I wonder what else is automotive on that engine.
 

Boomyal

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Re: Help understanding OMC cooling system - Control Box

Ayuh,... Welcome Aboard,.... Strange lookin' exhaust manifolds,...

What's it say on the side of 'em,..??

It is a strange looking setup for an early OMC. I think the whole thing has been cobbled together. Look at how the foreward bilge wall has been fubared.
 

Hibbitz

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Messages
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Re: Help understanding OMC cooling system - Control Box

Yea.... as I said I am not sure what is left of the original set up. I know a number of things have been replaced.

The manifolds are Barr Marine and they are a very early Camelback style.

I've purchased a new marine starter but didn't look at the distributor yet. Is a marine unit required if this engine is going to be run in an enclosed environment?

Don - Thanks for help with the identification of the voltage regulator. Is there any info on the site where you got that diagram? I haven't been able to find a wiring diagram for the boat yet but hopefully I can find one that will tell me where those wire should be connected to.

Thanks for the help guys!
 

captk

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Messages
252
Re: Help understanding OMC cooling system - Control Box

Also OMC never put a 350 to the Electric drives, they cant handle the torque. be easy on the throttle. that box is most likely the regulator. it may or may not wire up with what you have. and as has been said you have to get rid of that dist. good luck Bill
 

bruceb58

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Re: Help understanding OMC cooling system - Control Box

Also OMC never put a 350 to the Electric drives, they cant handle the torque. be easy on the throttle. that box is most likely the regulator. it may or may not wire up with what you have. and as has been said you have to get rid of that dist. good luck Bill
He has a Jet drive and already mentioned that the 350 replaced a 307.
 

captk

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Re: Help understanding OMC cooling system - Control Box

The 305 replaced the 307 and the 350 replaced the 327. they all have way different hp and torque curves.
 

bruceb58

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Re: Help understanding OMC cooling system - Control Box

The 305 replaced the 307 and the 350 replaced the 327. they all have way different hp and torque curves.
LOL :facepalm: :facepalm:
You need to read the original post:
The engine was originally a JX 245 which was essentially a chevy 307 that was mated to a Jacuzzi jet drive. I know the block is now a rebuilt 350 but I am not sure what else is original.
 

Hibbitz

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Re: Help understanding OMC cooling system - Control Box

Thanks for the help Bruce.

A picture is worth a 1000 words....;)

Jet_No_Plate.jpg


I'll do some more research on the distributor and swap it out but I am just curios if it is an issue around a non-spark unit like the marine starters or if it is that (and maybe as well as) or more of any issue with how the advance works.

Again, thanks for the comments
 

bruceb58

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Re: Help understanding OMC cooling system - Control Box

I'll do some more research on the distributor and swap it out but I am just curios if it is an issue around a non-spark unit like the marine starters or if it is that (and maybe as well as) or more of any issue with how the advance works.
Both.
 
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