1963 75hp Cooling Anomaly - RESOLVED

[yorab]

First of all, great to be back reading some interesting posts here again.

​Quick summary: I finished my engine rebuild back in 2011 and immediately moved out of the country. Nearly every component was replaced during my rebuild.
The boat and engine has been stored since then. I'm back temporarily and I'd like to get some hours on this engine. I have probably 10 hours on it total.
​I now have a weird cooling issue that I just can't figure out. I have a pretty good understanding of the cooling system, but I'm stumped.

​Current problem: I have a hot condition on the port cylinders, especially the top. It's running around 210 degrees on that top cylinder. The thermostat never seems to open because I'm not getting any spittle out of the upper exhaust port. I realize that there never is a full stream from there, but I've seen this thing working properly in the past spit some water when the thermostat opens. Now, no spittle at all. I just replaced the old impeller (ha! it only had 10 hours on it), because I wanted to rule out brittle vanes (the impeller was nice and supple but I replaced it anyway).

​I tested the vernatherm and it opens around 145 degrees (designed for 143). The vernatherm is NOS. I have another vernatherm with about 20 hours on it and its behavior is identical. The pistons on each push out about 1/8 of an inch or so. I went to the marina today and they allowed me to test a vernatherm that they had in stock. Its behavior was identical to both of mine. So, 3 different vernatherms acting the same. I must assume that they work properly.

​I'm definitely getting water flow because I disconnected the hose at the hot water choke and I have a solid stream from there.

​Just to rule out some things, I then took the thermostat guts out and idled her at the dock. The heads were of course cool (~110 degrees) and there was a good spittle coming out of the upper exhaust port.

​I can't figure out why this thing is hot with the thermostat components installed. I have more info, but I don't want to write a book on this post. If you have advice, I can let you know if I've tried it yet or not, and what came of it. Any ideas?

 

[yorab]

BTW, here is a video of the upper exhaust port in action with the thermostat removed. This shows that water is flowing well through the cooling system. Again, the engine remains too cool with the t-stat removed. I realize that under normal conditions, the spittle will be somewhere between very slight and what is in the video. I also realize that this won't be binary--it's not full open or full closed. Instead it's a balance between the t-stat and the bypass valves opening, but there should always be some amount of spittle. I am getting no spittle, even after the engine is clearly too hot (>200 degrees).

https://drive.google.com/file/d/0B8xDd3fDFA6xVVhHenJIZlZpTXM/view?usp=sharing

​I can only think that the vernatherm and valve aren't working properly when installed. The spring was mounted correctly.

 

[F_R]

That clearly is normal for with the thermostat removed. It sounds like you have a pretty good grasp on how the system works. I've put on my thinking cap, trying to come up with an answer for you. I'm thinking something related to the automatic choke, but can't decide what.

 

[yorab]

Here's another video that was recorded back in 2011, but the behavior is exactly the same today (I forgot to record video when I tested this last weekend). The water flow a moment after start up is very good from the starboard bank to the water choke. This, and the spittle in the other video with the t-stat removed, show that the impeller and water tubes are connected and working properly.

https://drive.google.com/open?id=0B8xDd3fDFA6xcVFjcWxQYURZWE0

 

[F_R]

They say that education is what you have left after you have forgotten everything you learned. Well, 60 years ago, I knew that system backward and forward. But now?? Well..

Ok, normally when the thermostat is closed, water pressure forces the relief valve open and water returns to the water pump, via a second water tube. My thoughts are that it is not happening. Does it have the correct relief valve spring? Or is there a blockage somewhere beyond the relief valve preventing the water return?

My second thought is that if the water is not returning, there would be no flow with a closed thermostat and the cylinders would overheat. But why just one side? Aha, look at the stream coming from that choke heater hose in your video. That is a significant flow--enough to somewhat cool the starboard bank at idle. FYI, after going through the choke, that water returns to the water pump without going through the relief valve. Do you have the choke plumbing connected? With that kind of flow, it must be reducing the water pressure presented to the relief valve.

So, I don't have an answer to the mystery, but these things should give you some things to ponder.

 

[yorab]

Thanks F_R. I'll think about these things and look it over when I get down to the dock today. In the meantime, to jog memory, here are some pics of the thermostat housing from different angles. Some of these pics are of the original thermostat housing and components and some pics are of the NOS components that I installed.

https://drive.google.com/open?id=0B8xDd3fDFA6xcVB5MjlGaTA0N1E

 

[Joe Reeves]

Does this 1963 model V4 still incorporate a Overheat Bulb or have you replaced that with a Warning Horn? In either case, does the warning device engage, indicating a overheat condition?

Did you water test the engine before storing it for 6 years, and if so... did this condition exist at that time?

 

[yorab]

Haha! F_R, you have trouble remembering every tiny detail after 60 years. Well I forgot EVERY detail just 6 years later! I had to re-read all my manuals and review old posts to try to figure out what the heck it was that I once knew.

​I believe that the relief valve leads to the return pipe to the pump. It seems to me that the relief valve is always open, thereby causing to the water to stay in the circuit and get too hot. When I'm not experimenting and I have all components are in my t-stat housing, the starboard bank also gets too hot (~170ish), but it is not as bad as the port side at ~210 degrees.

​Normally, when the hot water heats the vernatherm, the thermostat valve opens. This is basically a "dump" valve that expels the too-hot water into the exhaust stream. The drop in circuit water pressure closes the relief valve so that cool river water gets pulled into the circuit by the impeller and this balancing act continues as warmer or cooler water is introduced to the vernatherm.

​If the t-stat valve doesn't open, at least 2 things will happen: 1) the engine will run hot because cool water won't be pulled in, and 2) no water spittle will be ejected at the exhaust port. Right now, this is exactly what is happening for me. It seems that very little, if any, cool water is coming into the system and it seems that the t-stat valve won't open for some reason.

 

[yorab]

Joe, I do have the bulb. It was NOS and worked properly when I installed it during my rebuild. It did not engage this time, but perhaps that is because the starboard bank where the sensor is mounted, is not getting hot enough even though the port bank is really hot.

​I water tested the engine 6 years ago and it worked well, though I do remember that it was running slightly hot. Let me search my old posts to figure out where I was with that.

 

[yorab]

I just went back and looked at an old post. The port bank was reaching about 190 degrees before the t-stat valve opened and cool water was pulled in. The bank then lowered to about 150 degrees. I clearly remember that there were some obvious signs when the t-stat valve opened: I saw the water spittle increase and there was a difference in the engine sound--not bad, not good, just different. Perhaps that is due to acoustic characteristics of water shooting into the exhaust stream when the t-stat valve opens.

​In my current situation, water spittle is not evident at any temperature and the bank temp doesn't drop.

 

[yorab]

I couldn't figure anything out this weekend.

​F_R, I do have the return hose connected from the water choke to the port side of the adapter plate and I can now see what you mean about it returning down the port-side water pipe back to the water pump without going through the relief valve (first pic).

​I'm trying to understand the system better. Please tell me if this is correct:

During the first phase when the engine is first started, the pump pulls lake/river/sea water through the intake and pushes it up into the cylinder banks then down through the outlet ports on the bottom of both cylinder banks into the t-stat housing (2nd pic). Until the system is "full" of water, both valves in the t-stat housing remain closed due to the spring pressure on each valve in the housing. Some water at the top of the SB bank is always routed to the water choke, then into the water pump return pipe via the port-side nipple on the adapter plate. Once the system is "full" of water, the pressure begins to overcome the relief valve spring.

​During the second phase, the full-pressure water is not hot enough to open the t-stat valve, so water is recirculated through the system via the t-stat relief valve and via the water choke return line and no "new" water is introduced from the lake/river/sea.

​During the third phase, the hot water expands the vernatherm against the spring pressure, thereby opening the t-stat valve. This allows the too-hot water to be dumped into the exhaust. This dumping of water decreases the system water pressure, so the relief valve spring forces the relief valve to close. This in turn pulls "new", cool water into the system until we arrive back at the second phase.

​Is this exactly what happens? I'm trying to master this to have any chance of figuring out where my problem may lie.
​BTW, I have a million pics of my engine in various stages of assembly, so if you'd like to see a particular component to jog your memory and don't have quick access to it, let me know and I'll post a pic.

 

[F_R]

You have said it better than I could, and you seem to have it right. About the only thing I might add is there is always some new water entering the system, even when the t'stat is closed. If I remember it correctly, there is a groove in the 'stat vernatherm valve that allows some water to exit when closed. This is necessary to cool the exhaust when the stat is closed, and why it should discharge some spray even if cold.

I learned the hard way that the restricted hole at the water inlet side of the adapter plate (bottom of your first picture) is important in that it causes a water pressure differential / circulation within the block. But I don't remember exactly how it does that. The way I learned is because on the old OMC stern drive that hole is big (not restricted) in the adapter plate. Instead of a restricted plate, the stern drive has a restricted hole in the gasket. So, if you use an outboard gasket in a stern drive, you don't have the restriction and the powerhead will overheat big time. Yeah, I did it. I don't think all this is a problem in your case, just tossing in something I learned.

I hope you don't have the two springs mixed up (I don't know if that is even possible). Just thinking out loud.

I'm going to be pre-occupied here the next few days. Hurricane coming and we are right in the projected path.

 

[yorab]

Stay safe F_R.

 

[Joe Reeves]

If you haven't tested the overheat bulb yet, do as by having the key in the ON position, then grounding out the sensor wire at the cylinder head.... Good idea to make sure it's functional.

 

[yorab]

I'll definitely do that this weekend Joe as added insurance since I know that I'm having cooling issues.

I dipped the sensor in hot water before I installed it and it, along with the bulb, were working properly. I can't remember at what temp the circuit closed though.

 

[yorab]

Sorry about that--double post

 

[yorab]

Now I'm trying to figure out some last details about the water flow. As F_R already pointed out, the water to the cylinder banks comes up through the restricted hole marked as #1 on the adapter plate in the first pic and into the unrestricted hole in the block, also marked as #1 in the second pic. Water flow from the water pump also seems to feed the exhaust cover area marked as #2 in all pics. The block seems to have a 90 degree hole drilled to divert the water flow from the adapter plate to the exhaust cover area.

​This is probably very similar for many years and models. Can somebody confirm if this is correct?

​Also, how exactly does the water flow through the exhaust cover area and return?
How exactly does it flow in the cylinder bank areas?
​How does water flow in the water bypass area shown by the large cavity in the last pic?

 

[interalian]

The main waterflow on newer crossflows (and I would assume the older ones are the same) comes into the exhaust cover then through the slots in the center rear of the block, then into the area between the cylinder banks as seen in your last picture. From there, the water flows out under the lower cylinder, around the block in a figure 8 using rubber deflectors between the block and cylinders. It then passes through a hole in the head gasket, goes around the combustion chambers and out the top into the cylinder head water cover, then down and out the bottom through the rubber hoses to the thermostat area.

 

[yorab]

Thanks interalian. My engine doesn't use deflectors, so perhaps there are some differences between the crossflow and non-crossflow models?

​I see on the forums that there are water flow diagrams available but unfortunately, one is not included in the 1963 service manual

 

[yorab]

This is the water passage that F_R was referring to that allows water to pass even when the t-stat valve is closed. Seems incredible that enough water can make it through that tiny groove.