Is a 1974 OMC Sterndrive Raw Water Cooled?

[rdh2059]

This is a completely newbie question, but one important enough to me to ask, so flame away if you feel the need...

I have a 1974 26' Tollycraft, powered by two OMC inline 6's, and OMC Electric-shift Sterndrives. I cannot identify anything that even remotely appears to be anything like a heat exchanger, so suspect this uses external water as the cooling medium. Is this indeed true? Is it a closed system and I missed some details? Is it even possible to set up this engine/sterndrive combination to be a closed system?

Thanks,
Rick

 

[Haut Medoc]

Re: Is a 1974 OMC Sterndrive Raw Water Cooled?

If you have an idea what a heat exchanger looks like.....
Cylindrical with a radiator cap.....
& you don't see it, I'd have to say that you are raw water cooled....
Check the hose that comes into the engine from the transom, if it goes directly to the engine, you are raw water cooled......
Unless those are new engines, you are way past any hope of going to a closed system.....:'(
The general rule of thumb is one year/100 hours......JK

 

[Bondo]

Re: Is a 1974 OMC Sterndrive Raw Water Cooled?

Ayuh,........

If you can't find a Radiator Cap on or around those motors,.....
I'd say you probably have a Raw Water Cooling System......

Is this a Saltwater boat,..??..??.....

 

[DukesFin]

Re: Is a 1974 OMC Sterndrive Raw Water Cooled?

Water comes in to the outdrive in the cavitation plate, (right above the propeller... Look for a round screen there).

It goes from there, into the intermediate housing, then out through a hose that leads to your engine, (front side at the thermostat housing, right above the belts).

Raw water cooled. Don't change it at this point. If you put in a heat exchanger now, the rust that has accumulated in the manifold(s) will dislodge and "clog up" the heat exchanger (a problem you cannot fix).

 

[rdh2059]

Re: Is a 1974 OMC Sterndrive Raw Water Cooled?

Thank you everyone for the information. This is indeed a saltwater boat. Sounds like I use what I have, in its current configuration...

rdh2059

 

[Haut Medoc]

Re: Is a 1974 OMC Sterndrive Raw Water Cooled?

Flush it after every use & keep a close eye on the mans/risers.........

 

[rdh2059]

Re: Is a 1974 OMC Sterndrive Raw Water Cooled?

Flush it after every use & keep a close eye on the mans/risers.........

So how do you flush the engines on a 26 foot boat with twin engines, if the boat is moored in the water?

 

[Haut Medoc]

Re: Is a 1974 OMC Sterndrive Raw Water Cooled?

Bring the drives up, put the muffs on, lower the drives, run engine.......
Raise drives remove muffs......
Your engines , manifolds & risers will last much longer if you do that.......
I can't stress it enough......d

 

[bjcsc]

Re: Is a 1974 OMC Sterndrive Raw Water Cooled?

Hey, your setup has lasted for 32 years...sounds like it's working pretty well to me...but flushing it is a better than good idea...I can't believe your blocks have lasted this long without flushing...

 

[Haut Medoc]

Re: Is a 1974 OMC Sterndrive Raw Water Cooled?

Me neither....

 

[Boatist]

Re: Is a 1974 OMC Sterndrive Raw Water Cooled?

If it is in Salt Water and not flushed there no way it lasted 32 years.
Someone Has changed it.
Average life about 5 years before it plugs up or leaks water into the engine.