So far my issue seems to be resolved. But I'm curious as to how the wrong head gasket would result in cooler temps?
Once the block, heads and manifold are charged with water and retained by the thermostat, what role does a head gasket play in engine temps? (Assuming you don't have water escaping because of the gasket.)

I appreciate the laugh thou , thank you

I don't know what your name is, but if you'd like to correspond like an adult, I'll certainly welcome it. However, if you're more interested in juvenile talk, making derogatory comments, making assumptions without actually reading what was written, etc., then don't bother responding with your insults, as I didn't come here for that. I came here to collaborate with like-minded people who potentially experienced the same or similar, in hopes of improving it, and potentially helping someone out.


Back to the topic, if you're actually interested.

See answers below:


I have aluminum heads, therefore, they dissipate heat rather quickly at idle, so the idea was to keep them warmer for a smoother idle.

When I tuned my carb, I tuned it after the engine was was at full operating temp (Obviously). However, after coming off plane and letting the engine idle for roughly 5 minutes, the RPM's would drop about 180-200 from where the idle was set. That's strictly as a result of cooler head temps.No it`s not, how in the world did you come to that conclusion? You just blatantly say, "NO IT'S NOT" without knowing any of the specifics or other variables. Are you a Guru Mechanic, Professor in Physics? You have all the answers? The only thing you said was, "don't worry about it, mine runs cool all the time, no issue." (To that effect). I never said I was concerned about my engine breaking because it was running cool. The engine runs great, but the idle fluctuates and the oil temp took forever to rise. (I've since corrected the oil temp by installing an oil thermostat.) When I started this post, I didn't mention my idle issue, as I didn't want to steer people's opinions in different directions about what could be the cause of my idle issue. The water topic would have been hijacked because it doesn't seem like a likely cause for the idle issue. I wanted to focus on water temperature only, as I had already exhausted all other options.


In my particular case, I am saying that there is direct correlation with the water temperature, temperature of the heads, and curb idle. My manifold vacuum and curb idle were set when the engine was operating a full temp (heads over 160 degrees), as it should be. Idle was set to 850-870. However, within about 5 minutes of just idling (post warmup), the head temps would drop from 160 ish down to 116-120 (water temp would drop to about 100-110) There was a direct correlation between engine RPM and head temperature. I would watch the RPM drop as the water temp would drop. I'd rev the engine until the head temp would rise about 40 degrees, decrease the throttle back to idle and my RPM would resume to 825-850 (where it should be), as the temp would drop again, so would the RPM (down to 700ish - borderline stalling point).

I literally did this over 20 times under different conditions, and it always came back to head temps. Prior to considering that water temps had anything to do with this, I changed my distributor weights and springs in case they were sticking, thus advancing my timing. I checked my valves in case any of them were sticking and causing a vacuum leak / idle surge. I changed my ignition coil in case the voltage was fluctuation at higher temps. I replaced the manifold gasket in case it was leaking. I replaced my plugs and wires, I rebuilt my carb and did other various things, but to no avail.


I then consulted with the engine shop that built my engine, but they were baffled. I then got in touch with a former head mechanic of Mercury Canada. After explaining the symptoms, the trials and tribulations, it was he who speculated that my head temps were probably running too low, especially being aluminum heads with a raw cooling system. That's when I started looking into the water temps. Obviously that mechanic knew what he was talking about.


My objective was to increase water temperature as a means of eliminating the idle issue and to promote a faster rise in oil temperature. WHAT!? Increased water temperature = increased head and manifold temperature, which results in a more efficient combustion at idle, thus a stable/constant idle speed. Warmer engine block = linear increase in oil temp, at least up to the thermostat setting. Optimal combustion is at 170ish degrees, therefore, there's certainly going to be a negative effect on combustion efficiency if the head temps drop by 50 degrees. There's a reason why you tune a carb when you're at full operating temp and not when it's cold. My thought process is this, if I can maintain a water temp of 140ish at idle, or above 120 at the very least, then my head temps are certainly not going to drop below that temperature. I'm sure if they were cast iron heads they would be 30 - 40 degrees hotter at idle,even with ample water flowing through them.


As indicated in one of my final posts from last fall, I said I was going to remove the welded restrictor/washer from the crossover, as I suspected that might be the issue.

Anyway, I did so two weeks ago. I put the boat in the water, fired up the engine, warmed it up to 110ish, increased the RPM to 1,200 for about 3-4 minutes, and lo and behold the water temp rose to 144-145 and stayed there. That has never happened before. When I reduced the RPM to idle (850) the temp lowered to about 125-130 after 3 to 4 minutes and stayed there. Temp goes up with more RPM and lower with less? That`s great info Captain Obvious!! What`s your next great discovery, ice melts in the sun? Here you go again, another smart ass comment without actually reading or comprehending the message.

Point being, the water temperature has never climbed to 144-145 with the RPM's slightly increased, while in neutral, and it has always dropped to 100-110 when set to idle.

So, when I said I reduced the RPM to idle and the temp lowered to 125-130 after 3 to 4 minutes AND STAYED THERE, it wasn't a discovery of how lower temps and lower RPM's are linked and vice versa. (You truly thought that I was trying to educate the group with their ABC's?)

The point is, the temperature did not drop more than 125-130, as it normally would have, and my curb idle didn't drop below 800 RPM. Think that's a coincidence? I don't think so.


As for ice melting in the sun, well, the sun actually heats up the water beneath the ice, and in turn the heated water melts the ice from the underside, and warm air melts the surface of the ice as it passes over it. The darker areas along the shoreline (sand, rocks, etc.) absorb heat from the sun and and transfer it to the water, again heating the water and causing the water to melt the ice. (Just In case anyone else wanted to know, as I'm sure you already knew that.)


Again, if you'd like to correspond like an adult in a cordial fashion, by all means, please do so. I'm also open to constructive criticism without taking it to heart, as I don't pretend to know more than I do, and I'm always open to learning something new. Hence why I came here. But don't insult me, and I'll show you the same respect.

Not sure why you are so against the factory recirculation system as it would fix the coolant temp and etc issues you are facing.

Yes, I have witnessed the difference in idle and planing rpm aluminum vs cast iron heads cause in terms of quality. The fuel puddles and has less vapor to ignite when head is cold. Wet fuel does ignite well or at all. However, adding some more initial timing and just a 1/8-1/4 turn more idle fuel then best hot engine idle setting solves the rougher idle and low rpm planing cough. Massive difference in cold start and drivesbility.

What is your initial timing ?

BTW: many here with roots superchargers and big cammed engines run a ton of initial timing fir a reason. Think of the distance of cold aluminum surfaces on roots blown motors and tunnel rams.

Dude, six pages of water flow issues. Drilling holes, wondering, asking, measuring, concocting theories.

just a thought here. Why not just go to a stock circulating pump, and mercury thermostat housing setup, and go boating?

Another thing. With all your crazy temperature fluctuations, did you ever verify the proper head gasket was installed? Because if the wrong gasket was installed, with the front coolant hole open instead of blocked, the water will short circuit and you will have very uneven head temps, especially the rear cylinders.

Agreed.

[QUOTE=MILD THUNDER;4745596]Dude, six pages of water flow issues. Drilling holes, wondering, asking, measuring, concocting theories.

just a thought here. Why not just go to a stock circulating pump, and mercury thermostat housing setup, and go boating?
As I said earlier, if what I did a couple of weeks ago solved the issue, great. If not, I'll install a pump, as was the plan if all else failed.
I didn't leave a post a few days ago to resurrect the issue. I came back to say, "I think I got rid of the issue". And to thank all for their input. That's all. This is a good thing! Lol

Another thing. With all your crazy temperature fluctuations, did you ever verify the proper head gasket was installed? Because if the wrong gasket was installed, with the front coolant hole open instead of blocked, the water will short circuit and you will have very uneven head temps, especially the rear cylinders.
I referenced the part numbers for the gasket and heads from the engine build specs, and they are the correct gaskets for the heads. At least on paper.
Is it necessarily the wrong gasket that results in the front coolant hole being left open? Or is it an optional gasket depending on build type? Just asking because I want to make sure. It's certainly something to considering.
Thx./QUOTE]

Please fix your quoting and replies in the two posts above. Hard to follow. Thanks.

The problem with the gasket is the block. If you install a gasket designed for a Mark IV block, on a gen V or VI block , the front coolant hole in block will be exposed. The water then enters front block, and goes right up to head and out thermostat. At low water volume, such as idle, it can cause some big temp fluctuation. Most fel pro gaskets will fit all three versions of the big blocks, but theres still a few that only fit mark iv blocks.

Do you know what head gasket was used, and what version block you have?

The block classified as a Mark IV and Gen VI. Part #19170540
Head gasket - Fel Pro #17048

Thx