Water cooling problem - 6hp Evinrude 1977 long shaft

[Sigean]

Hi,

A few days ago I raised a problem I have with my old 6hp Evinrude. No cooling water from the normal exits when running the engine, just an initial stream (less than 10 secs), then a few splashes and vapour, then steam. I have tested the pump (new impellor) by driving the drive shaft with an electric drill and the pump ejects water from the top of the drive leg - the pump appears to work fine. This overhauled 6hp engine starts and runs well, has a new thermostat, and I have checked the water cooling passages and these are clear. New gaskets are fitted. After running the engine until the steam emerges from the water outlets (both the tell-tale and the exit on the drive leg) the thermostat is wide open, but apparently no water is reaching the top of the cylinder block. I have no idea what else to investigate as the pump seems perfectly capable of this duty - am I doing something wrong? Do the long shaft engines suffer from cooling problems?

Any advice welcome...

Peter

 

[JDusza]

Re: Water cooling problem - 6hp Evinrude 1977 long shaft

You may have a water tube grommet issue.
I have just completed a rebuild of an over heat that happened even with water coming out of the telltale. The water flow was nowhere near enough. I initially thought the water pump impeller, but, when I opened her up the impeller and it's drive dog were fine. Replaced them anyway top eliminate the worry.
The problem turned out to be the upper water tube grommet, the one that sits inside the exhaust pipe flange. It was all messed up for someone had put it in upside down and it got squashed partially closed. Apparently, it ran ok for a couple years and eventually got heated and deformed to where it wouldn't let enough water through. Aside from being in upside down, this is a fairly common problem. They will wear out.
How did you troubleshoot the water coming up through the drive leg? Was the water tube in place inside the water pump? The top edge is flared to hold the gasket in the exhaust pipe. Does your water tube have the flare?
There is nothing odd about the long shaft engine. It should function just as a short shaft.
J
p.s., welcome to the forum!

 

[Sigean]

Re: Water cooling problem - 6hp Evinrude 1977 long shaft

Many thanks and the issue of the grommet is an interesting idea, one I had discounted as I am able to push a cycle brake cable through the cooling tube from the pump and out where the water emerges at the joint at the top of the leg. I thought this test suggested that the tube - and grommet - must be clear. As for testing the pump, I removed the engine from the drive leg, then put the drive leg (with gearbox and prop) into the flushing tank and then rotated the drive shaft with an electric drill. I pushed a rubber hose into the water exit at the top of the drive leg and at max drill speed the water flowed out of the little hose at a level about where the top of the cylinder block might be, and tis kept on coming for all the time I ran the drill - minutes.

The "acid test" for me is that from cold on starting the engine the cooling water p*sses out of the telltale, and out of the exit halfway down the drive leg! 20 secs later these flows start to sputter and eventually turn to steam. Something else is happening - can this be explained by a faulty gromment?!

Any further thoughts welcome and I will check the grommet anyway as I am about to tear the enginer down (again....).

Peter