Lots of air from the tell tale?

[MadCityMike]

This is a 1972 65 hp to which I've added a tell tale to help diagnose an overheating problem. The water pump is new and seems to be pumping water well, but I'm still overheating. The tell-tale has a LOT of air coming out with the water spurting under considerable pressure and as it gets hotter it turns into mist and then just air. I'm guessing the air pressure gets to a point that the water pump can't push water up. The air coming out is not smokey like the exhaust. Does air pressure in the waterjacket mean bad head gasket? Cracked head or block? Something else? I took some pictures of it running because it has water coming out of places I'm not sure it's supposed to. I drew arrows in all of the places where water is coming out.

Port side: water stream coming out of the front just above the cavitation plate which I believe is normal, but a lot of water is coming from where it mounts to the hinge. Also quite a bit coming from the base of the exhaust adapter. I took off the shroud to see if water was coming from somewhere else and just coming out there, but as you can see, it's just the front.

Rear view: You can see water streaming out of both sides of the hinge mount. Also, you can see the mist coming from the telltale.

Starboard side: Pretty much a mirror image of the port side with the tell tale as well.

I haven't had this motor long enough to know if water is supposed to be coming out of all of those places or not. It does run very good other then when it's overheating.

 

[iwombat]

Re: Lots of air from the tell tale?

You need a bigger bucket, or some muffs to diagnose this properly. I think your motor is sucking exhaust/air into the water pump. You need to get water HIGHER than the water pump when running in a bucket. You're not even getting up to it.

 

[MadCityMike]

Re: Lots of air from the tell tale?

Sorry, I should have mentioned that there are muffs on it. The bucket is just to give a bit of backpressure and to quiet it down. One other thing: Compression test shows 75/75/80 psi.

 

[iwombat]

Re: Lots of air from the tell tale?

In that case, it would indicate an air intrusion from a headgasket or other source. Given the two streams out the side, I'd say you didn't connect the water inlet pipes correctly, or they have a leak.

One more comment: You should be using the bulkhead fitting for the tell-tale outlet. It looks like you're just routing the hose out. That'll rob too much water from the cooling system and cause an overheat. You need to reduce the outlet.

 

[kenmyfam]

Re: Lots of air from the tell tale?

Drop it in the lake and give it a real test. Water comes out of every orifice it can find on the muffs !!!

 

[jay_merrill]

Re: Lots of air from the tell tale?

Yes, the pee stream coming from the lower, front of your exhaust housing is normal. The two streams coming out of the sides in your photos are not. My guess is that the hose pressure is what is blowing water out of the hinge point.

My first inclination is to say that something is partially blocking the water pump inlet, but its hard to say without going through a trouble shooting process. You should probably drop the gearcase, to see what is going on with the water pump and inlet passages. If you have not done this before, be careful of the shift wires - do not let the gearcase drop before you get the connectors separated! If you let the gearbox drop to a point where strain is put upon the wies, they may break and that is big trouble, because the wiring assembly that runs through the exhaust housing is NLA!

Your cylinder head has a cover on it, with another cover for the thermostat. That may be another area for problems. Additionaly, there are two poppet valves in the area of the t-stat, which open when water pressure (rpm based) reaches a certain point. My guess is that these are not the problem though. I mention them merely because checking them if you get into the t-stat isn't a bad idea.

As for the compression values, they are very low for your motor. Original values would have been in the 150 psi range. This may be cause for pulling the cylinder head to see if you have a bad gasket. If you end up pulling both the head and its cover, new gaskets will cost you about $60.

One thing that I don't see is where you tapped the cooling system for your tell tale. Can you post a pic or two of that?



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[jay_merrill]

Re: Lots of air from the tell tale?

Just an afterthought - you do have the muffs on the horizontal inlet grooves, right? The vertical grooves that are located above the cavitation plate, right above the forward portion of the prop shaft, are the primary exit point for cooling water. If you have your muffs over these, this would account for both the lack of cooling water in the system and the water blowing out the side of the swivel bracket pivot point.



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[Rick.]

Re: Lots of air from the tell tale?

Good thinking as usual Jay. Never occurred to me. Rick.

 

[pmat1]

Re: Lots of air from the tell tale?

When you put the l/u back on, did the rubber/plastic piece on top the impeller houseing not connect with the mid section right? just an idea

 

[MadCityMike]

Re: Lots of air from the tell tale?

I tore into the head this evening and sure enough, the head gasket was pretty much rotted. Each cylinder had rot holes, but the middle cylinder had it the worst. Hopefully this explains the overheating problem along with the high air pressure at the tell tale.

One of the thermostat housing bolts snapped off a while ago when I had replaced the thermostat, so since the head was already off, I took the opportunity to remove the head cover to fix that problem as well and that gasket turned out to be pretty nasty. More then likely original. Since both the head gasket and head cover gasket were rotted pretty bad, should I be concerned about any of the gaskets on the exhaust side? Are there any water passages on the exhaust side?

Jay had asked about where I tapped my tell tale. I did it on the hot side of the thermostat. Here are some pics.

As you can see, it doesn't interfere with the action of the thermostat at all. Yes, it's a 1/4" barb fitting, but it gets necked down to 1/16" at the pee port, so I don't think it allows too much water through..

It's going to take a couple of days for the gaskets to show up. Any suggestions on anything I should do while the head is off? There is a very small amount of scoring on the #1 cylinder wall, but they all look pretty good otherwise.

Thanks for the help.

-Mike

 

[jay_merrill]

Re: Lots of air from the tell tale?

Before getting into the exhaust cover gaskets, I would finish with the head. After reassembly, run the motor to see what the cooling situation is like and do a compression test.

I usually try to stay away from pulling exhaust covers, if I can. Sometimes you have to get into them, but if a bolt is going to break on a motor, thats usually one of the prime locations for it to happen. Also, if you do have to pull the cover, you will have to pull the powerhead first, because you can't get at the lower bolts (lower cowl is in the way), without doing so. If you end up doing it, don't forget that there is a stud in the back of the powerhead. It fits down into the exhaust housing adapter and has a nut on it, that is accessible from the inside of the cowl. You can't see it when looking down from the back of the motor - look for a slot and feel for it with your fingers. Once you find it, getting a wrench on it is pretty easy.



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[MadCityMike]

Re: Lots of air from the tell tale?

Just a followup. After replacing the head gasket I now have a nice steady stream of water from the wee hole instead of tons of air and spurting water. I took it on the water last night and it runs like new now. Thanks

 

[kenmyfam]

Re: Lots of air from the tell tale?

Just a followup. After replacing the head gasket I now have a nice steady stream of water from the wee hole instead of tons of air and spurting water. I took it on the water last night and it runs like new now. Thanks

Good to hear. Enjoy.