TOPIC: Another Old Rude rides again !

Well guys, I hooked up the battery, spun her three times briefly, hooked up the fuel and primed it, puched the button for the electric choke which actually works (!) and pulled the trigger. She fired in less than 10 seconds and purrs like a kitten. Problem is I think I may have put the impeller in wrong. There's nothing coming out of either the exhaust hole or the 2 small ones below it. Which is the correct exit for cooling water ?? What else could be wrong ?? It's an amazing motor and I can't hurt it now. What should I do or try ?? ANY ideas at this stage are welcome. Thanks for all your help so far guys !

Did you check to see if the telltale hole was plugged? I have had that happen more than once - everything was working but there was a spiderweb or other junk blocking the water outlet. Try taking a wire and running it into the telltale outlet. Sometimes that frees things up.

Outside of that I would wait for one of the experts to chime in who is more familiar with the motor. What is the model / year?

It's a 1961 Evinrude Super Quiet Big Twin 40 HP. That's a good idea and I'm going to dump the bucket and do that while I'd be otherwise waiting. It sat for four years so you may be right.

Okay I'm a dummy. This motor has the exhaust coming out just above the prop and that upper hole must just be a blowoff. The question is does my water exit with the exhaust through this aperture and should I even be looking for anything coming out of the shaft ?? Can you spot the telltale hole ? I don't know what I'm looking for.

remove and check the thermostat. there may be some junk stuck in the housing. and remember that it takes some time for the thermostat to open. and make shure that the water in you barrel is high enuf to cover the water intake. Bob

Thanks Bob. We did that while I had it out and it popped at 145 by my thermometer. I need a new gasket (I'll make one) for the housing and we broke one of the three screws so we tapped that out and put in a temp. I'm replacing all three as they are in rough shape. Other than some fuel lines and trying to find a picture of the motor's original appearance so I can paint it correctly things are rolling right along

Water should be coming out the upper hole where you expected it to (at least that's how it is on my '59 35 hp). I recently had a similar problem and it turned out that I had let the key slip out of the impeller when I reassembled.

Mine won't fit in without the key. I was wondering a lot about that but Ed said to remove the thermostat from the housing and if water shot up it was working fine. I haven't run the motor for more than a couple minutes but another fellow (sorry) said that mine won't pump anything out until the thermostat opens. I just haven't run it long enough to hit running temp yet. She's going to the lake for that. I don't trust the little bucket I had to use. I'll lat you know. If you're right I should find out pretty quickly. I hope I'm right Thanks Dave.

If there was a problem down below, you wouldn't get water up to the powerhead. So no worries there.

First time in the lake, with a 'stat in there, fire it off & let it idle.

Feel the exhaust cover to make sure it's not getting extremely hot. The exhaust relief won't spray much water until the thermostat opens up.

First time the 'stat opens, you'll get a shot of steam along with the water, if you see that, it's normal. After that, it should be spraying pretty good. When underway you should get a forceful spray out of the relief.

I'm sure there must be a good place in the block to drill and tap for a water telltale fitting. All you need is a 1/8"-NPT fitting then mount a telltale nozzle in the lower cowling and run a hose in-between. It'd sure be nicer than guessing if there's enough water flow when you first start it up.

Maybe a fitting in the top of the thermostat cover would work, ya think? HMMMMMM............!

Have fun at Sea Trials and let us know how it goes.....ed

As I said, sorry Ed. I couldn't remember who I was quoting but I believed you and you were right. On more than one occasion with this motor I might add. And thank you again. So drill a 1/8" hole in the thermostat cover and tap ? Easy enough. I'm cutting a new gasket for it anyway so that's gonna fit in the mix. Any particular location ? It's a 3 bolt.

No Worries, Shipmate!!

Before getting ahead of ourselves, it'd probably be a good idea to figure out the direction of water flow thru the head. Been a long time since I've looked at one of these. It's possible that there might not be any water at the top of the thermostat cover until the 'stat opens up. Since you did run it without the cover, you might recall where the water was coming from.

The idea is to tap into a place where the block sees water pressure directly from the pump, before it hits the thermostat.

So maybe a bit more studying is in order before we drill holes! I was brainstorming and don't want to lead you down the wrong path.

Maybe try it again without the cover and see where the water comes from. If you can see that it flows to the top of the thermostat before the 'stat opens, then a hole in the 'stat cover would work. Otherwise we'll need to figure out a better spot for the fitting.

BTW a 1/8"-NPT fitting takes a special tapered tap such as this one:

www.amazon.com/Vermont-American-20371-Carbon-Steel/dp/B000K1LZ76

Drill size for that hole would be 11/32". So wherever you drill, it's gotta big a big enough surface to take the tapped hole which is over .4" in diameter.

I found a nice FAQ at iboats about adding telltales to some of the newer OMC motors that didn't come with one, lots of good info there even though there's no mention of how to do it on a Big Twin:

forums.iboats.com/forum/engine-repair-and-maintenance/engine-frequently-asked-questions-faq/228380-johnson-evinrude-adding-a-tell-tale

I found a few good pics on eBay including some showing the cylinder side of the head, they illustrate the complex water flow thru the block & head. If I had a block in my hand, I could stare at it a while and probably figure out where it goes, but haven't really given it that much thought before!

Hope that helps a bit.......ed

When I tested it after talking to you I removed the top of the housing and pulled the stat. When I started it water shot straight up and out the hole where the stat had been. In the bottom picture it's on the top right. Lots of water coming out going up. Would a picture of the inside of that housing help ?

Firstglassproject wrote:

Would a picture of the inside of that housing help ?

Yup!

I think I have an idea of which way the water circulates, after sleeping on it. Check out the pics of a thermostat cover.

You'll notice at the top of the head (on the head gasket side) there's a passage that goes up at an angle to the thermostat. I believe this is the water feed, up from the pump, and circulating thru the exhaust manifold & block before going to the thermostat.

The plastic insert that the thermostat rests on has a slot which, if I'm correct about this, points towards the angled hole.

Such that water flows up underneath the thermostat, where the temperature sensing element lives. When the thermostat opens, it routes water flow upwards, thru the 'stat cover, then over to external water passage you see going down one side of the head.

This passage exits the bottom of the head and is dumped into the center section, what you see as water spraying out the exhaust relief.

Another way water gets down to the exhaust is that spring-loaded check valve at the bottom of the thermostat insert. If you were to take off before the 'stat opened, if there wasn't a point of relief you'd overheat the engine because the 'stat wouldn't allow enough cooling. But water pressure will overcome the spring pressure and water will dump freely down the side-passage, and again out the exhaust relief.

If the above is all correct, then anywhere that can pick up water pressure from under the 'stat, will properly feed a telltale. It won't matter if the thermostat is open or closed, since water is in that part all the time.

I don't know if that angled passage would be thick enough to take a tapped hole. Or maybe the thick, flanged part of the head where the cover sits.

Anyway, maybe an OMC Guru has a water flow diagram for Super Quiet Big Twins or a good idea for telltale location. I can think of other places to put one, but it'd entail unbolting the cyl head cover or exhaust manifold cover and that's a bit of work and gaskets.

HTH........e

Here's mine as disassembled. What's the best way to clean that rusty coating from in there ? This thermostat works fine but I'm going to replace all the screws and put in a new gasket. If there was one it's gone now. Getting that little ball stop centered when replacing the thermo's housing can be a PAIN. Stiff wire or a small screwdriver work. That's the inlet (?). And there's my cap.

Clean 'er up with a scraper and wire brush. The little Gordon "toothbrushes" are good for working in tight places.

Sure does look like water flow is up the angled passage at the top of the head, thru the plastic slot and to the under-side of the 'stat.

So, to get a telltale in there you'd have to figure out the best place to drill/tap a fitting.

Another option would be to find a press-fit hose fitting and precisely drill a hole into which the fitting would be tapped. A bit of red Loctite around the fitting and it'd never come out.

This would take a much smaller hole than the 1/8-NPT fitting and might, for example, be able to drill right into the side of the thick flange on the head, into the cavity under the top of the 'stat.

Such that there would always be water pressure on the telltale line, whether or not the thermostat is open.

Thanks for posting those, exactly what's needed to figure it out....ed

Thanks Ed. My Merc buddy and I will be going into this on the weekend. He knows far more than I but not much about other outboards so your info and diagrams have helped BOTH of us learn as we go.