Cold seize prevention

[bloodman]

After popping my 250xs powerhead due to cold seize 2 years ago I am now very cautious about running in cold temps. I now let the engine cycle through the thermostats before taking off and then I watch the temp to make sure it does not drop to an extreme on acceleration when the poppit opens. I just recently returned from a 2 week trip to northern Minnesota and have the following observations.

All of these observations are after the idle warmup is complete.
Acceleration while the temps are at the highest or while droppping will cause a great loss of temp under acceleration. I think this is because the poppit and t'stats are open at the same time.
Acceleration after the temp reaches minimum or barely rising will cause the least amount of temp loss. I believe this is because the t'stats are closed and even if the poppit opens during acceleration the t'stats being closed will hold the temp better.

Considering these obsevations it is my belief that you have the least chance of cold seize when you wait to accelerate after the temp drops to minimum and the t'stats are fully closed rather than when the temps are dropping and the t'stats are open. Any other thoughts on this.

I have no doubt that my cold seize was cause by a rapid temp loss on acceleration when the t'stats and poppit were open at the same time.

[taeheel2az]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by bloodman &raquo;</td></tr><tr><td class="quote">I have no doubt that my cold seize was cause by a rapid temp loss on acceleration when the t'stats and poppit were open at the same time. </td></tr></table>

Waalll, , , , ,

The cold sieze happened because the piston was expanded from heat and the cylinder was not yet hot enough to have made the corresponding expansion.

The thermostats opening indicates that the block and cylinders have "caught up" with the pistons. The block now has a lot of latent heat and is further heated by combustion as PRMs and water pressure rise enough to open the poppet. Water flow through the poppet and thermostats is not nearly enough to overcome the latent and combustion heat and cool the block enough to shrink the cylinder to a cold siezure situation.

There's a rapid drop in water temp, but the pistons and cylinders remain hot.

Some plain and fancy engineering to make all this happen right.

[EuropeanAM]

+1... most cold seizures occur due to one of the following:

-Lack of proper warmup on EVERY startup(operator error)
-Sticking open thermostat (debris)
-Lack of proper COOLDOWN or Temp stabilization before shutdown

Make sure that you achieve AT LEAST 120 degrees on Smartcraft BEFORE ACCELERATING.

After a run, allow the engine to idle 45-60 seconds, while monitoring to ensure engine temps "stabilize" in the 120-145 degree range (varies, based on engine model).

[Phoenix Jim]

what kind of lake temps are we talking about here. My lakes are like 50 right now

[bloodman]

The lake temps now are in the low 40's.
All I am saying is by watching the smartcraft temp fluctuate for 16 days on the lake, I believe you are better off waiting to accelerate when the t'stats are closed.
I can gaurantee that my engine was properly warmed, the t'stats were not sticking and there was no debri. I can also attest that I watch my smartcraft temps religiously.
While idling my temps fluctuate. You can see when the t'stats open and when they close by the fluctuation in temps. There is a distinct difference in temp while idling. Temps even out while on plane but not while idling in cold water.
I believe part of cold seize problem can be attributed to that rush of cold water hitting the cylinder wall when the tstat and poppit are open at the same time under acceleration.
Seems like a high percent of cold seize issues have occurred right after acceleration and I believe what I stated above may be a contributing factor.
Anyway, I will be waiting to give her juice until I see the t'stats close.

[nacoa]

MY 225 proxs only gets to 116 on a warm up. I only get to 120-130 when i am running. if i wait until 120 to start I will be sitting there for a while.

Oh, I am in Florida so the water tems are still in the 70's but my temps have been this way since I repowered in July.

Is this something I should be concerend about?

What should be my norm operating temps at idle and full out?

[TRCM]

you may have a sticking stat.

[crizzel]

From my experience if your T Stats have debris in them then your not going to get to 120 until you blast off.. When I had debris in mine it wouldnt get over 110..

[EuropeanAM]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by nacoa &raquo;</td></tr><tr><td class="quote">MY 225 proxs only gets to 116 on a warm up. I only get to 120-130 when i am running. if i wait until 120 to start I will be sitting there for a while.

Oh, I am in Florida so the water tems are still in the 70's but my temps have been this way since I repowered in July.

Is this something I should be concerend about?

What should be my norm operating temps at idle and full out?

</td></tr></table>


Unless you have SUBSTANTIALLY cold water temps- your engine should EASILY reach 120 degrees MINIMUM.

I would strongly recommend removing and inspecting your THERMOSTATS... you very likely have debris in one of them (or it is sticking open).

THIS type of problem is the most likely cause of a cold-seizure, BTW.... we recommend monitoring temps to ensure at least 120 degrees on Smartcraft BEFORE accelerating.

Since thermostats work independantly of each other... it's going to be quite difficult to specifically monitor to ensure both are closed (unless viewing temps on the Computer Diagnostic System)... so some of the comments above in this post aren't really something you can accurately put "into practice".

I can tell you that on 3L models.... if you have a thermostat hanging open, the engine just isn't going to reach 120 degrees AT IDLE during warmup.

[Phoenix Jim]

any chance someone could post a pic of the thermostats? I have an 08 250 pro XS. Is this kind of inspection covered in the service manual which I have been meaning to buy? Thanks
PS: Just ordered a service manual from Don!


Modified by Puma Jim at 7:27 AM 11/10/2011

[runninrusty]

does this warm go for EFI motors as well

[crizzel]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by Puma Jim &raquo;</td></tr><tr><td class="quote">any chance someone could post a pic of the thermostats? I have an 08 250 pro XS. Is this kind of inspection covered in the service manual which I have been meaning to buy? Thanks
PS: Just ordered a service manual from Don!&lt;br /&gt;&lt;br /&gt;
Modified by Puma Jim at 7:27 AM 11/10/2011</td></tr></table>


The Tstats are right above the heads.. Can't miss them. Might want to get the gaskets for the Tstat housings from Don if you tear them while removing the housings.

[EuropeanAM]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by runninrusty &raquo;</td></tr><tr><td class="quote">does this warm go for EFI motors as well</td></tr></table>

Yes sir- it DOES. All engines benefit from proper warm-up and cool down, and it's ESPECIALLY critical on 2-stroke models (which have open ports in the cylinder sleeves).

Here's a picture of a 3L Optimax Thermostat where the engine would only reach 101 degrees (the "cause" can be seen lodged in the thermostat):

[esdbass]

Don: Any thoughts on why cold seizes are seemingly more common on 3L than on the 2.5's

I can see where a Nik sleeved 2.5 might have more resistance but on Steel sleeved 2.5 motors I wouldn't think there would be any difference yet it would seem you hear about this more on 3L ?

[EuropeanAM]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by esdbass &raquo;</td></tr><tr><td class="quote">Don: Any thoughts on why cold seizes are seemingly more common on 3L than on the 2.5's

I can see where a Nik sleeved 2.5 might have more resistance but on Steel sleeved 2.5 motors I wouldn't think there would be any difference yet it would seem you hear about this more on 3L ? </td></tr></table>

Good question. Some of the differences that contibute include: Bore diameter, Cooling passage SIZE, water flow VOLUME of the system (cooling capacity), exhaust port size, and PISTON SPEED.

[hemi1]

when warm up i get over 120 but on plane drops down to 90 degrees
in water around 50 degrees is this normal?

[esdbass]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by hemi1 &raquo;</td></tr><tr><td class="quote">when warm up i get over 120 but on plane drops down to 90 degrees
in water around 50 degrees is this normal?</td></tr></table>

I don't want to speak for Don here but depending on your water pressure and how much throttle you are giving it at the time I could see temps dropping to around 90* something when the T stats open.

I think the more important issue would be that you should not after coming off plane re accelerate BEFORE your temp goes back up to at least 113-115 range.

Think "warm up" and "warm down" always with these motors

[EuropeanAM]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by hemi1 &raquo;</td></tr><tr><td class="quote">when warm up i get over 120 but on plane drops down to 90 degrees
in water around 50 degrees is this normal?</td></tr></table>

+1 on Eli's comments.

Your results above are perfectly normal- and here's why. You have TWO DIFFERENT water flow control modes built into your engine:

IDLE/Low RPM Circuit: This is THERMOSTATIC Control. Thermostats control the flow of water, opening at their setpoint temperature, and regulating the engine's temperature to ensure it reaches proper operating temperature.

MID/WOT RPM Circuit: This circuit is the POPPET VALVE function. As you reach approximately 2000-2500 RPM's, the poppet valve begins to open, creating a STRAIGHT THROUGH water flow for the engine block. Once the poppet valve is open, the thermostats are essentially non-functional, until RPM's drop (and the water pressure falls to a point where the poppet valve again closes).

When the poppet valve is open (higher RPM's.... with water pressures above approximately 7 psi)... your engine's temperature will be more affected by lake water temps. This is why on plane temps can range from the 130's in very warm water, to the 80's in very COLD water.

It is critical that the engine, once decelerated, be given time to "recover" thermostatic control, and stabilize the engine temps to "thermostatic temperature" (at least 120 degrees).

[herk91]

Don There has been a lot of chatter about EFI's and Opti's, but what about CARB motors? How long on warm up before putting the Hammer down? Especially in waters around the 50 degree mark.

[LeeinAlabama]

On the warm up do you need to let it idle for 5 minutes every time you crank it or just the first time which is usually in the morning. Just got my 1st Merc. a 300XS and I want to treat it right. Probably won't be my last post so I apologize if I ask some elementary questions and thanks in advance for the help and tips.