Waterpump? 1960 40 HP Evinrude Mystery

[KirbyE]

I'll do my best to be clear. Model 35520 S# 23821<br />I'm getting this old thing running. Bought it used with no promises. Impeller looks and feels fine to me. Soft, pliable, and not really worn looking. In a test tank, it idles, warms up, then stops pumping water. With the plugs removed and the starter turning it, water is restored. I removed the thermostat and same thing. It gets real hot real quick while trying to tune the ide mixture etc. No teltale spray (scavange) after 30-45 second. I crack the seal for the thermostat housing to monitor the waterflow, and I can see it stop after revving a bit, then never return. There is no prop on, and I have only rarely even put it in gear to open the throttle. The impeller key and hub are all intact, and I'm confident the waterpump is assembled properly. With no water the automatic choke never heats up, and so on. The thermostat does work, but I have removed it as a variable, literally. I put a garden hose on the copper tubes from the pump and it appears there are no clogs.<br />Is this a resonable failure mode for an old impeller? I read somewhere that it behaves as a displacement pump at low RPM and then becomes a centrifugal pump at higer RPM to deliver the same volume in each case. The impeller seems fine to me, but clearly I will replace it ASAP and post the results. (Part # would be a help, BTW).<br />Any other ideas ??? What am I missing? The waterflow doesn't slow, it STOPS. I even filled the tank up to the steering bearing just to be sure. <br />Thanks in advance, I'm "DITW" until this resolves. <br /><br />OBTW, how do I get this flywheel off? Custom Puller? Heat? Thanks. Kirby.

 

[Joe Reeves]

Re: Waterpump? 1960 40 HP Evinrude Mystery

Install a complete water pump kit which includes everything...... There are no short cuts. And also, re-install the thermostat assembly as that engine must run at a specified temperture.<br /><br />A flywheel puller must be used that incorporates bolts that will line up with the three threaded holes that surround the flywheel nut.<br /><br />Be sure to torque the flywheel nut to 105 foot pounds when re-installing the flywheel. Any less will result in a sheared flywheel key and damaged flywheel and crankshaft tapers,

 

[KirbyE]

Re: Waterpump? 1960 40 HP Evinrude Mystery

"complete water pump kit which includes everything" <br />What else besides the obvious impeller? I never got the "kit" before. Is it available from Sierra or other aftermarket?<br />Any other insight?<br />Maybe the impeller swelled, and thus the tips drag close to the hub? Has to stop to get back to form? Just thinking out loud.<br />Thanks. Kirby.

 

[krb113]

Re: Waterpump? 1960 40 HP Evinrude Mystery

Check your compression also. My 40 hp Ev had a blown head gasket and wouldn't pump. My conpression was 112 top and 120 bottom. Put a new head gasket on and She's peeing now!!

 

[KirbyE]

Re: Waterpump? 1960 40 HP Evinrude Mystery

How do you explain that? There must have been a blockage. I don't see how the two relate. Glad to hear you are in good shape.<br />Kirby.

 

[krb113]

Re: Waterpump? 1960 40 HP Evinrude Mystery

With the blown head gasket, the pressure that leaks back into the water jacket is stronger than the pressure that the water pump gives out. I have never read what the pump pressure is, but it is basically like a washing machine pump. It only needs to get it up to the drain pipe turn around, if you will, and then it is done. <br /><br />I, at first, was skeptical because I really never thought about it until a wrencher at the marina put his money on the gasket. The ol' boy didn't come over here on a bannana boat evidently! That was it!<br /> <br />The fact that you have an engine with a t'stat and mine does not, may have a different affect from some other scenario. Just don't rule the head gasket out. Good luck!

 

[KirbyE]

Re: Waterpump? 1960 40 HP Evinrude Mystery

Holy cow, I would never have thought that. 112 & 120 would not cause me to think a problem was there, but I better look. Any way to test without removing the head? Compressed air in cylinder? It's never been off in 45 years, and one broken bolt and I'm done. Also, where can I get the head gasket?<br />Thanks again.<br />BTW: I made a puller and got the flywheel off.

 

[krb113]

Re: Waterpump? 1960 40 HP Evinrude Mystery

I, too, didn't think the reading variation was that significant and with the plugs out and spinning it over it would push your thumb off the plug hole pretty good. I told him that I left the compression gauge of for a couple of minutes, and both leaked down about the same. He said nope! That's no good to tell as the schrader valve on the gauge will leak down usually. To really tell, use a "leak down gauge" (for lack of my knowledge of the proper term for said gauge) and it will be the truth teller so to speak. I didn't have one. I just trusted his expertise as I was on "skid row" with this situation.<br />Use PB blaster on the bolts and let them soak if you are planning to go this route. It does wonders in my opinion and use.