Outdrive impeller replace with a raw wate pump

[John Smith]

On a 1972 OMC 225 stern drive, Does any one know this ever been done, putting a Raw water cooling pump which bolt to the side of the engine with a fan belt, drill a hole though the bottom of the boat taken water directly from there, push into water exchange(Close cooling system), I saw this crazy idea in one of the repair forum, he said his mechanic install this for him and this solve all the complex water pump system in the OMC out drive, Does anyone know the out drive need any water to cool it down or when the out drive submerge in the water most of the time should be sufficient to remove the heat build up by the gear in high rpm. Some of the raw water pump has a kid now you could remove the back plate and change the impeller in less then 2 minutes. I be appreciate if anyone out there OMC mechanic or know the OMC cooling system very well could give me some input. Or if such system already install in some OMC boat would not mine share the diagram how to do this. Thanks viewing, you could see this water pump in http://www.triton381.com/rwpump.htm

 

[Walt T]

Re: Outdrive impeller replace with a raw wate pump

The water pump in the drive doesnt cool the drive. The drive is cooled by the outside water. I have never done this conversion, but have seen it done, No apparent problems. You will still have to remove the impeller from the drive, you know.

 

[Bondo]

Re: Outdrive impeller replace with a raw wate pump

Why remove the old impeller, Walt ???? I'd just leave it there, till i had the outdrive apart the next time....

 

[John Smith]

Re: Outdrive impeller replace with a raw wate pump

I would guess that the water running constantly over at least the lower gear case (even while on plane) it would be sufficient to keep the oil cool enough in the lower unit. What about the exhaust and steam constantly running through the upper and intermed. drive when the boat in up in the plane and the gear is raping in high RMP there is no more water around the upper and intermed gear case? But may be the Raw Water Pump pumps the cold water cooling the exchanger and then continues on to the exhaust intact, upper and intermed gear case that may me sufficient to keep it cool. Any suggestion how this raw water pump should connected? Or the raw water pump should use as an additional assist to the impeller?<br />John 1/9/03

 

[charleswmoore]

Re: Outdrive impeller replace with a raw wate pump

I would definetly remove the old impeller. Since the impeller is still trying to pump water it would have to be diverted some where?? Also the <br />chances of the impeller eventually wearing through the pump plate causing damage to the shaft seals are high. In the OMC drives (later model) this is an easy task. I think it is an<br />excellent idea. Maybe use Volvo parts to make the conversion to the thermostat housing / exhaust manifolds etc..It should be pretty easy???? Refere to a 1979 to 1990 AQ260 for plumbing.

 

[John Smith]

Re: Outdrive impeller replace with a raw wate pump

Yes, Definitely I will remove the impeller from the out drive to prevent break off in the future and cause blockage in the circular system. The Plumbing plane you mention, I could not get the web to search AQ260 1979-90, may be I am not using the search correctly? Also any idea what pump(pully or crank driven) and size of output is most reliable for a V8 307 GM ? <br /><br />John 1/14/03

 

[butch290]

Re: Outdrive impeller replace with a raw wate pump

John,I'm interested in what you are doing. my omc 800 stinger shoots water on the ball gears, and I'd lose that if the water pump wouldn't push pressure up through outdrive.i made a new post on my problem.

 

[John Smith]

Re: Outdrive impeller replace with a raw wate pump

Someone had given this idea in another board. The cooling of the upper gear case can be accomplished with a T off some water from the big jabsco and feed it down where it normally comes up. And perhaps put a restriction at the inlet/outlet screen to slow it down after the impeller in the drive has had it. It sound very good any input will greatly appreciated<br />John 1-16-03

 

[charleswmoore]

Re: Outdrive impeller replace with a raw wate pump

Back in the old days my father had a early model<br />omc 1970 and I was pretty intimate with the pump /<br />cooling water routing. From my memory I recall the water was routed into the boat via endcaps <br />that supported the drive. Yes it had a tell tale <br />pee hole but i never recall any incomming cooling water bypassed to cool the external ball gears.<br />(Maybe exhaust cooling water bypass on the way out the stern drive????) By design the pump was mounted in the upper section and it was lucky to cool the system without any additional leaks. I wouldn't try to bypass anything. Also if you look <br />at jabsco pumps in Freeport Marine or Boat US you will find the pump. Their was two, One was a higher volume recommended for southern climates.<br />(Moved more water) Also see Volvo's Home page<br />they now have a parts cat. on line. Most likely best bet would be to look at a engine repair manual for Volvo (Seltic (Spelling ?))See below links its pretty good.<br /> http://www.penta.volvo.se/t/002.asp?id=6&p=1 <br /> http://www.stemtostern.com