Cooling circulation trouble

[srimes]

So I put in a new impeller and added a telltale on my '79 70hp but it doesn't look right. I took a picture and added comments:

Almost nothing comes out the telltale. When I revved it I got a little squirt. Maybe it'd be fine on the water???

A lot of water squirted out the weep hole above the cavitation plate, and it took a long time to drain from there after I shut it off. Also, the water here was pretty warm, almost hot.

Any ideas what the problem could be and how to fix it?

 

[nathanhooper]

Re: Cooling circulation trouble

The same thing happened to me on my 70hp 1973. Do a search of my name and you can read the story, its long though. What I am getting at is I would be curious if it does the same thing after I get it all back together and running again. But I, like you, wondered why the water coming out was so stinking hot. I assume that is what you were thinking anyways.

I also wondered like you why it was coming out of that little hole. I am halfway convinced that there might be something clogging my internal passage ways, after all the sand I have found from taking the motor apart. I wonder if it could be the same for you too. This is one of the reasons why I was curious if anyone had a diagram of how water flowed through the engine. Hopefully someone will have some advise, hang in there. But for now it might be advisable to take your thermostat out and check it.

 

[srimes]

Re: Cooling circulation trouble

Hey I was looking through your post and see how you've torn the engine apart but didn't see you really talking about cooling other than asking for a diagram. Do you have a link to the post? Also, what's the bypass valve? I see where you asked about replacing it but not why you took it apart.

When I had the lower unit off I put the garden hose on the water pipe and water squirted out the telltale, so I know it can flow.

Is there supposed to be a gasket or something where the water pipe fits in the pump housing? It seems like pressure would be lost there.

ps. where abouts in Arkansas are you? I've been in Cabot for a year now.

 

[nathanhooper]

Re: Cooling circulation trouble

It was in the long post somewhere, I thought. It was not a specific thing that I pointed out in great detail because I replaced the seals on the L.U. and moved on to the motor. I am thinking it was coming from one of the seals, crank shaft seal is the one I am thinking it was, the one right underneath the impeller.

I took the by-pass valve apart to check on it. In my manual it says that over heating will continue to occur if it is not functioning. That is why I am confused on here now. Popular opinion is that running without your thermostat is not right. I guess it all boils down to whether or not your engine is cooling.

That is good to know about the the tell tale. I was curious what the flow is so that when I add my tell tale I could tell where water was supposed to flow to first. Sounds like it comes up through the block and then down through the heads.

There is a seal that fits on top of the water pump housing. Attached is a picture. Circled in red is the seal. I live in NWA

I will have to attach a picture when I get home, sorry, it wont let me right now.

 

[srimes]

Re: Cooling circulation trouble

I went to check the thermostat to see how it look, but it wasn't there . I guess someone pulled it trying to fix the cooling problem. Also, there's blue RTV squished out around the cylinder head cover. Is there any reason to pull it and see what it looks like under there?

I checked compression and got 135,136,125 top to bottom. Squirted oil in #3 and it went up to 140, so it looks like rings. But I'm going to hope it's just carbon buildup and when I decarb it it'll all be OK :redface:.

I pulled the pump again and am putting a light coating of silicon on each surface just to be sure I'm not losing pressure there. Part of me wants to put some on the water tube/pump housing joint but I'd probably regret it at some point. I stuck the hose on the water tube again and yes, it flows out the telltale fine, so I think it's good from that point on. But that's from the hose, I don't know how much volume the pump is supposed to put out.

Oh, and I grew up and went to school in Fayetteville.

 

[john from md]

Re: Cooling circulation trouble

The water pump puts out high volume but low pressure. Is your telltale connected to the port next to the thermostat housing?

The water/exhaust coming from the two small holes in the mid leg is the exhaust pressure relief (the first arrow in your picture). This allows the engine to start without fighting the exhaust back pressure caused by water pressure at the Snout. ( the secondt arrow in your picture)

The thing you call a weep hole is a drain hole for the midleg. There are several of them around the flange that the attach bolts go through. You should not get water from these holes unless the leg is submerged. If you are getting water from these holes when running on muffs, you have a leak either at the water pump housing or in the line going to the powerhead.

John

 

[nathanhooper]

Re: Cooling circulation trouble

Small world, I grew up in Springdale. Here is the one diagram. Once again I was not able to upload the pic from my camera, but you should see where there is a rubber seal of some sort on top of the pump housing that the tube fits into. I do not know if it is on all L.U.'s, but it is on mine.

John, thanks for your post. It makes a ton of sense now where the water comes from. I have seen a lot of people ask that same question about the little hole there. I bet it is a issue with the tube not lining up and leaking like you were talking about.

I read somewhere that you can take a straight edge and set it on the matting surfaces of the leg and l.u., then take a tape measure and measure the distance the water tube sticks out and then the distance to the seal on the pump housing. Then you can tell how far down the inlet tube slides in when bolted up.

That way you can see if you are just barley in it, which would lead to it leaking there.

Correct me if I am wrong srimes, but you put your tell tail in where that little threaded plug is on the very top of the heads right? Where the thermostat sits into?

 

[srimes]

Re: Cooling circulation trouble

Yes, my telltale is plumbed in to the port on top by the thermostat housing as described in this thread: http://forums.iboats.com/showthread.php?t=210027

I think I'm missing the rubber water tube seal, if you can post the pic I'd appreciate it. If anyone knows when I can order one that'd be great, if not I'll try to rig something up. I put grease on the end of the water tube and slid the lower unit on, and pulled it off to see how far the pump went up the tube. It slid on leaving about 1/16 clearance from the pump to the outer ring on the tube, so I cleaned off the grease and put a fillet of silicon there to try and form a gasket. Haven't tried running it yet but we'll see.

I just had another thought. The telltale port is right by the thermostat housing, and there's no thermostat in there providing resistance to water flow. There could be plenty of water flowing through the housing without sending water through the telltale. There would need to be enough flow and restriction on exit to make the water flow up and out the telltale. I'll test my theory by putting some resistance in there to simulate the thermostat, like a fender washer. Once I get it working I'll order a new thermostat ($30??? For a thermostat??)


As for the water coming out the drain hole (what I labeled weep hole), I looked at the leg and the whole leg is open, and that's where the exhaust and water travels down. Since my driveway is sloped the motor was tilted forward, and any water mixed with the exhaust would tend to go down the front of the leg and out the drain hole. I don't think there's a bad leak where the water tube meets the powerhead because when I put the hose on it I could hear the motor fill up for a couple seconds and then water would start pouring down the leg, so I'm guessing that is what it should do. I bet if I turned the boat around so the motor was leaning back that not much water would come out that drain hole.

 

[nathanhooper]

Re: Cooling circulation trouble

I will make sure to post the pic tonight. Good call on the grease thing. I am going to do that myself just to make sure I am getting a good seal. I would also check the top of the tube where it connects with the block. There may be a leak there, but I would also think that if it were that loose it would fall out when you remove the l.u.

As far as water pressure and it not having enough restriction, I would also think it would be a good idea to test your theory, but I am thinking just from water dynamics, that it would still have some flow out of it if you were getting adequate flow. But I will leave that one to the experts. And yes, the thermostats are stinking expensive, but I think I have found them for around $15 somewhere on the net before. I am hoping mine will still work well enough to use again. It opens, and they say as long as it opens and closes, then it works. And now that I think about it, when it does open it opens a good ways, but it is definitely not like having nothing in there, so there would be some restriction. Let me know how your test goes.


I would might turn your boat around and test your theory on the weep hole also. Worth doing I would think.

 

[john from md]

Re: Cooling circulation trouble

Gentlemen:

Whether or not a thermostat is installed, water will come out of the tell tale. However, since the water pressure is only about 2 PSI, any bug that builds a nest in the tell tale will stop the flow. Blow some air through the tell tale to clean it out. If your water pump is working properly, water will come out of the tell tale in about 30 seconds.

Another check you can do is to hold your fingers on the relief holes at the back of the leg for about 10 seconds. When you remove your fingers, you will get a flow of water for a couple of seconds. This is a good indicatior that your pump is putting out enough water.

The seal on top of the water pump housing is called a Garlock seal. They are pretty standard seals and are used in many machine applications. It will need to be pressed out and the new one pressed it.

Just so you know, there is a guy on ebay that sells an entire WP rebuild kit, to include the impleller for less than $50 bucks.

Regards,

John

 

[srimes]

Re: Cooling circulation trouble

WooHoo! It worked!

But first, I fired it up and got a little water from the telltale. Blipped the throttle and got a good stream that slowly trickled down. Definitely better than before I put on the silicone. Then I cut out a square from a cereal box and cut 5 holes: 4 for the thermostat housing bolts and 1 1/4" hole for water through the "thermostat." When I fired it up I got a STRONG jet of water shooting out the telltale! And some water leaking around the housing, but the test worked.

I had already ordered the thermostat and can't wait for it to get here. If I get a chance to take the boat out before it gets here I will as I know water is circulating now. And yes, I will watch for the pressure from the telltale to drop when the thermostat is open, but for now I think it'll work .


Thanks for the tip on the WP kit, I'll check that out the next time I change the impeller. Iboats didn't have one.

Now I can see if the new fuel pump will maintain WOT!

 

[srimes]

Re: Cooling circulation trouble

I'll also add:when standing barefoot in the puddle, don't try to feel how hot the thermostat housing is with wet hands while the engine is running! The spark can leak through/around the boot and wake you up good . Oh well, I've had much worse ::redface:.

 

[nathanhooper]

Re: Cooling circulation trouble

thats great. I am glad you figured it out, and more glad you posted the results. Here is the pic I promised. Although you may not need it now. Where did you get your thermostat and what did you wind up paying for it?

 

[srimes]

Re: Cooling circulation trouble

Thanks for the pic. Is it just like a fat rubber washer or does it extend down in to the pump at all?

I ended up ordering from iboats. It was $30, with gasket and shipping it was about $35.

 

[nathanhooper]

Re: Cooling circulation trouble

it goes down in the housing, i think. never have taken it out.

 

[srimes]

Re: Cooling circulation trouble

I put the thermostat in today. Fired it up in the driveway and got a good stream. Took it to the river and ran it, and at speed it looks like it stops flowing out the telltale. Should I worry? I stopped and felt the stream and it was hot enough that you wouldn't want to leave your hand it it, but was OK to briefly touch.

 

[nathanhooper]

Re: Cooling circulation trouble

That is interesting. I would like to hear some expert opinions on this. It sounds like it started coming back out after you stopped. Do you have an overheat alarm on yours?

 

[pnwboat]

Re: Cooling circulation trouble

I'm no expert but........water and exhaust only come out of the two holes in the back when you are at low speed or sitting still idling. Once you are under way, all of the exhaust and water get sucked out the exhaust opening under the cavitation plate.

 

[srimes]

Re: Cooling circulation trouble

Yeah I'm new to outboards so I don't know how hot the water out the telltale should be. And yeah, when I slow down the telltale starts squirting again. At some point in the middle of the rpm range (don't have a tach) it sputters and stops. I don't have an overheat alarm, at least not that I know of.

 

[srimes]

Re: Cooling circulation trouble

Hey nathanhooper,

That rubber gasket that goes between the water pump housing and the water tube: does it extend down to plug the holes in the side of the socket?

If they're NOT covered I'm thinking there's a reason, like it's needed to relieve pressure. I ran the motor in the driveway long enough for it to warm up and for the thermostat to open, and when it did water stopped coming out the telltale, so I'm going to pull the lower unit again and try to come up with a better seal. I think I'll try an o-ring or two.