Cold running an Optimax

[shermsmarine]

The first thing I want to talk about is cold water through a cold motor..
1) A outboard motor does not warm up very fast if at all at an idle in cold water.
2)Thermostats can only help it warm up so fast if you have 40 +/- deg. water running through your power head.
So how do you run a Opti or other outboard under these conditions?
1) Idle at least 3-4 minutes minimum.
2) Take off easy.....Do NOT hammer down from an idle while still cold. Take it easy for a ways. Increase the RPM's gradual.
3) Make sure your thermostats are working properly!
* This one is very important ... (I had this happen to me) I was running a 2004 225 Opti in 40 deg. water, motor was running at 130 deg range it picked up a pebble and stuck it in a thermostat (held it open) I had Smart Craft gauges and always have it on eng. temp in cold weather/water..
When the thermostat got stuck open it cooled the motor down to less than 80 degrees!...It would NOT go above 80 degrees even at WOT!
So what's the problem??
First you have a certain amount of clearance between the piston and cylinder wall.
example... cyl bore on a 200/225 Opti is 3.6265 in. (std.) The piston has approx. dia. of 3.6210... So you have approx. .0055 piston to cylinder wall clearance...
Now when a motor heats up it expands...So when it's up to normal operating temp. the piston and cylinder wall are both a larger diameter.
When you run a cold motor hard or up to WOT real quick what happens is the piston gets hot much faster than a cylinder wall that has cold water against the outside of it....The hot piston expands but the cylinder wall hasn't yet....What happens from there is called a Cold Seize.. The expanded piston don't have the .0055 clearance needed and it will seize or stick to the cylinder wall. If it seizes/sticks running @ 5500 RPM + it just rips the wrist pin/connecting rod right out of the piston...The connecting rod will go out of control and end up out through the side of the block...At this point the power head is destroyed...This is one of biggest failure issue of a Optimax and one that can be avoided by just following the above info.by making sure it warms up and has time to warm up right ........Sherm

[EuropeanAM]

Have them check the thermostats- one or both are likely sticking open due to debris.

A compression test (or better yet, a leakdown test) is always a good measure of the engine's current condition.

[otdrmn]

Hi guys, first time poster. Great forum by the way

I have a 2009 150hp Opti, question relating to operating temperatures (in Celsius)
Water temp 21c (69d), Motor temp at anything above 5knots is 33-38c (95d), at idle a temp of 68-70c (155-159d)

My question is how long can the motor sustain a operating temp of 68-70c, reason for question is I do a bit of slow trolling of live baits at just above idle speed.

Thanks in advance for any responses.

[EuropeanAM]

Hi guys, first time poster. Great forum by the way

I have a 2009 150hp Opti, question relating to operating temperatures (in Celsius)
Water temp 21c (69d), Motor temp at anything above 5knots is 33-38c (95d), at idle a temp of 68-70c (155-159d)

My question is how long can the motor sustain a operating temp of 68-70c, reason for question is I do a bit of slow trolling of live baits at just above idle speed.

Thanks in advance for any responses.

Welcome to BBC!

68-70c (155-159 F) is within the acceptable range for this engine at idle (though it's on the high-side).

VERIFY WATER PRESSURE at idle and WOT. If your water pump has not been REPLACED in the last 364 days... now would be the time to do so. Pay SPECIAL attention to the gasket UNDER the impeller plate (may be torn/broken).

Keep in mind... temps will fall rapidly as soon as water pressure reaches approximately 6-7 psi (not far above idle).

[cwill]

Great info guys. Just to reiterate all of this info and make sure I'm clearly understanding it. I want to idle after putting my boat in the water til my temp reaches 120F. This will keep from getting a "Cold Seize". After this I can ease into the throttle and get on pad which will drop my temp alittle but the "stat" will help it maintain a relatively steady temp. If I start to see that my temp has fallen and will not rise back up, to say back above 80F or 90F, I most likely have either something stuck holding my thermostat open or just a thermostat failure of some sort. I have the Smart Craft gauges on my 2007 250 Pro XS. I currently keep it so I can see the Water PSI. Should I change this to the TEMP setting?

[EuropeanAM]

Great info guys. Just to reiterate all of this info and make sure I'm clearly understanding it. I want to idle after putting my boat in the water til my temp reaches 120F. This will keep from getting a "Cold Seize". After this I can ease into the throttle and get on pad which will drop my temp alittle but the "stat" will help it maintain a relatively steady temp. If I start to see that my temp has fallen and will not rise back up, to say back above 80F or 90F, I most likely have either something stuck holding my thermostat open or just a thermostat failure of some sort. I have the Smart Craft gauges on my 2007 250 Pro XS. I currently keep it so I can see the Water PSI. Should I change this to the TEMP setting?

Your understanding is correct UP UNTIL you begin to go on plane.

Thermostats control engine temp AT IDLE (ONLY). Once you begin to plane off (approximately 7 psi water pressure) the poppet valve OPENS, allowing a straight-through flow of water. Hence, on plane temps will vary IMMENSELY, depending on load and lake water temp.

When you come OFF plane (back to idle), water pressure falls, the poppet valve CLOSES, and the thermostats again regain control of coolant flow (begin to control engine temp again). At this point- you should allow the engine to idle long enough to ensure it has STABILIZED at thermostatic (120+ degree) temp, prior to shutdown.

Not sure what Smartcraft Instrument you are utilizing... but it would be PREFERABLE to be monitoring BOTH Coolant Temp -AND- Water Pressure (most instruments can accomplish this... the EXCEPTION would be the old System Monitor, which only displays one data item at a time).

[cwill]

Does this tell you anytihng?20150302_152059-1.jpg

[cwill]

20150302_152059.jpg

[EuropeanAM]

That is not a Smartcraft Instrument (it's actually an Actia Gauge, that Champion was using).

[196 Bobby]

I've gotta ask. 2008 200 opti. Warmed up to 120 degrees in 59 degree water. Accelerated and temps stayed steady and rose to 127 degrees. No drop in temps. . 20 psi water on analog gauge at 5000 rpm. Decelerated and temps rose to 136 degrees. I dropped it at the dealer to inspect thermostats, poppet, strainer for compressor. Am I being paranoid or was I justified in a service call. New water pump installed last fall with 1.3 hours on it also. Temps via sc-1000 smart craft gauge.

[EuropeanAM]

I've gotta ask. 2008 200 opti. Warmed up to 120 degrees in 59 degree water. Accelerated and temps stayed steady and rose to 127 degrees. No drop in temps. . 20 psi water on analog gauge at 5000 rpm. Decelerated and temps rose to 136 degrees. I dropped it at the dealer to inspect thermostats, poppet, strainer for compressor. Am I being paranoid or was I justified in a service call. New water pump installed last fall with 1.3 hours on it also. Temps via sc-1000 smart craft gauge.

Good topic for a SEPARATE thread (including your engine information/serial number).

Also, be sure to provide the water pressure (in separate thread) for:

-IDLE SPEED (when engine was at 136 degrees)
-WOT (FULL RPM's... boat at maximum speed, not partial throttle).

[zelmo]

This is the first year I have been able to use the boat when the temps have dropped. Although I was aware of this thread I never went through it like I did today. Very helpful info.

I will install a SmartCraft gauge, but until I get that done I will need to take it easy and be careful to idle for a while. Current water temps near me are 45 degrees. After a run about how long does it take for the temps to drop? If I am fishing for a while and want to move do I need to idle for 4 minutes or will there be enough residual heat?

[EuropeanAM]

Difficult to answer accurately, as it will depend on YOUR thermostats, their condition, whether they have debris in them, and the water temps.

In a perfect world, at your water temps, APPROXIMATELY:

5 minutes on a COLD START

60 seconds idle after coming off plane (before shutdown).

However, without a Smartcraft Instrument to monitor, you're really "flying blind" (and the engine's PCM is limited to sending you "smoke signals").

[ddogopti]

So after reading this entire thread, there are numerous references to pebbles, chunks of wood, and other debris being stuck in thermostats. Is there any any reason why Mercury does not have inlet screens in the water intake on the lower unit? The first thing I noticed on my Opti are the inlet holes are large and no screen. I have had both Yamaha and Evinrude outboards, both use screens in the lower unit, and I have never found or had to pull debris of that size out of the thermostats and I have found the bottom on more than one occasion. It seems the solution for improved thermostat reliability already exists, curious why Mercury doesn't chose to employ it.

[EuropeanAM]

Side intakes are very different from LOW WATER INTAKES.

Installing a screen in this type of application would result in blockage plugging of the water INLET (which in turn would cause overheating, as well as a possibility of water pump damage).

This has been discussed at great length on the 3L forum, several times.

[yukonjack2]

I have a 2005 XR6 - I do not beleive it is smartcraft capable. What are the aftermarket options to get temps on both banks?

thanx

[EuropeanAM]

Please open a separate thread for your engine/question. Thanks!

[zelmo]

I wanted to come back and thank all who have put together the great info in this thread. Since installing my Smartcraft gauge I have gone through 2 spring seasons, a fall and a winter. It is comforting to know what to do to properly warm the motor up. It is also scary to realize that I ran it for many years not knowing the damage I could have caused. In addition monitoring the gauge tipped me off to stuck thermostats that I was able to clear.

Once again - thanks to all of you.

[MRichard2016]

Thanks for all that info Sherm! Hoping you and yours are staying safe..

This is Mike who bought the 2013 P4 from you...any chance you are still having deals on the Merc monitor/smart gauges?

[SilverFox579]

Sherm hasn't logged in since mid-January so you might want to contact him directly.