'59 RDS-21 - No water circulating

[racinmason]

Hey everyone! I've got a water circulation problem on the 59 Johnson RDS-21 35hp that I'm restoring.Resealed the lower unit along with a new impeller.The old impeller was in one piece.Ran it in a barrel (twice) with water up past the parting line of the L\U and midsection.Didn't get any water out the idle relief or out the thermostat housing(removed thermostat).Checked and made sure impeller was correct.I can get air and water up both water tubes,and down through the thermostat housing.I've seen previous posts for newer motors that have problems with corrosion around the water tube grommets at the block.Is this a problem with the older Big Twins also? I'm about ready to pull the powerhead to take a look,(the Seloc manual is really vague here),and if it's not that,the only thing I can think of is maybe a blocked water jacket? I'm scatchin'my head on this one! (By the way,compression is 105 on both cylinders)<br /><br /> racinmason

 

[CATransplant]

Re: '59 RDS-21 - No water circulating

Hmm...if the tubes are clear, you should be getting circulating water. One reason you might not would be a missing woodruff key in the driveshaft. That key is what actually turns the impeller. Do you remember installing the key? If not, and even if so, you should check to make sure it is there and properly positioned.<br /><br />With the thermostat out, your engine should begin showing water out of the idle relief within a few seconds of starting.

 

[rolmops]

Re: '59 RDS-21 - No water circulating

When you run that thing in a barrel you have to make sure that the waterpump is under water.It will not suck up any water through vacuum.

 

[Yepblaze]

Re: '59 RDS-21 - No water circulating

They won't spit water till the thermostat opens. At least as I remember. After a few minutes the tone will change as the water flows.

 

[racinmason]

Re: '59 RDS-21 - No water circulating

After a small delay, I got back around to taking a look at it again,and got water flowing thru the ol'Big Twin and she purrs like a sea horse!While I had it apart,I took and spun the drive shaft with a drill to make sure the impeller was pumping water,which it was.Later in the evening,while I was nursing a sore shoulder(from patting myself on the back),something occured to me.When I spun the shaft to test the water pump,I got water out of one side.Should there have been water coming from both outlets,or is the other a return?Since everything was working right,I'm thinking it is,but I wanted to be sure!BTW,I want to thank everyone on the iboats forums!I learned a ton and I could'nt have got 'er runnin' without you guys!<br /><br /> racinmason

 

[Paul Moir]

Re: '59 RDS-21 - No water circulating

The other is a return. The cooling system in your outboard is unlike just about any others. It more closely resembles an automotive system than an outboard system. Cooling water is recirculated through the water pump via that other pipe until it gets hot enough, at which point it's expelled through the big hole on the back of the outboard (idle exhaust & cooling water outlet) allowing room for fresh, cool water to be pumped into the system.<br /><br /><br />Good to check in though.