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Author Topic:   Four-cycle Engine Warm Up

pcrussell50 posted 06-15-2011 02:55 PM ET (US)
Is [the procedure described below] an adequate warming for a Mercury 90-HP FOURSTROKE with carburetors?
I haven't been able to use my boat for at least 3 weeks now, (though I start it on the muffs more or less weekly). I know and worry that merely starting it on the muffs for a few minutes is not enough to boil off any water condensation that has gotten into the crankcase. Well, yesterday, I hooked her up to the muffs, then got distracted with something else and forgot about it for at least 20 minutes. When I got back, the telltale stream was nicely warm, which I had never seen before, I suppose, because I had not let it run that long before. Do I have reason to believe that the oil got properly warm in this case?
My performance cars and race car have oil temperature gauges. I look at them all the time. I wish there were a sender so I could add one to this motor, (maybe there is?)
-Peter
Plotman posted 06-15-2011 05:13 PM ET (US)
I can't see why you feel the need to run a boat once a week on the muffs... And I can't see the value unless you let it get up to temp.
If it's going to be more than about 2 months, then maybe either run it out of fuel or run it on a remote tank of stabilized fuel so you don't gum the carbs up. Other than that, I believe you can be too anal about an engine.
pcrussell50 posted 06-15-2011 05:28 PM ET (US)
I'm in a unique situatuon... This motor is famous for having tiny little passages in the carbs that get gummed up easily. Further, it has a 12 gallon tank under the console. That amount of fuel takes me weeks to use up, since my outings are nearshore, and of short duration. Therefore, I always treat every tank with fuel stabilizer.
If run her on the muffs long enough for the telltale stream to become toasty warm, (not burning hot), can I assume the oil got warm enough to evaporate the condensation?
-Peter
Sixer posted 06-15-2011 07:22 PM ET (US)
Check the dipstick. No mention of your year, my 2007 EFI has one. The form of induction should not make a difference. The Merc SmartCraft gauge package might have the oil temp as an option in one of its data packs.
kwik_wurk posted 06-15-2011 07:28 PM ET (US)
Once a week, not needed. Flush it once after saltwater, and be done with it. (Once a month there after is more than sufficient, and before you head to the ramp.)
What makes you think you have condensation in the block? Sounds like you need to find that source more than you need to run the engine once per week.
Cold then warm water is expected once the thermostat opens up. Similar to a car, there is a bypass on the engine.
So if you only flush a cold engine for a minute or two you aren't helping it much. In fact you're doing more harm than good; the startup and stop process is typically the most taxing thing on the engine. (Excluding stuff like running constantly at WOT, or with a dinged prop.)
It takes 8 minutes on my 90 hp 2 stroke to get fully warm from a cold start. The telltale gets warm, but not hot warm.
As long as the telltale is strong, and there isn't sputtering with vapor (steam) you should be fine.
Tohsgib posted 06-16-2011 01:54 PM ET (US)
NEVER WALK AWAY FROM A BOAT RUNNING ON MUFFS!!!
If those muffs slipped off(which they do) you would have come back to a toasted engine after 20 minutes of no water. Run ringfree or run the engine out of gas but no need to run it weekly unless you are buzzed and have nothing better to do with your time....which I do every now and then.
zotcha posted 06-16-2011 04:57 PM ET (US)
Well your honest...and thats funny!
A2J15Sport posted 06-16-2011 09:36 PM ET (US)
It is far better to leave it OFF than running it a few minutes. Particularly with no load.
Some of the carbed four strokes were extremely sensitive to fuel quality and expecially fuel varnishing.
If is going to sit, for any extended period, treat the fuel.
I treat my fuel all the time. No worries.
weekendwarrior posted 06-21-2011 02:37 PM ET (US)
Running once a week is fine and will ensure your carbs stay gum free. Idle speed will most likely not get the oil hot enough to steam off any fuel or water in the oil, but when flushing after salt use it is important to run it long enough for the thermostat to open, at least according to my Honda manual which says at least 15 minutes flushing after salt use.
weekendwarrior posted 06-21-2011 02:40 PM ET (US)
I will also add that you should never get water in the oil. If you do then you have an issue that needs to be addressed. You may get fuel build up in the oil from extended low speed running (some motors do and some don't), but in most cases cruising on plane for a while will get it hot enough to steam the fuel off.
pcrussell50 posted 06-21-2011 08:29 PM ET (US)
Thanks, Warrior. Those were the tech-rich kind of responses I was looking for.
Nick, I never thought of that. I'm nearly 3 years into boating, and I thought I knew it all. And you're a crackup, as usual.
-Peter
Salmon Tub posted 06-25-2011 11:44 AM ET (US)
Get a large plastic tub/storage box and install a through-hull with a short hose. Running it in a tub of water is better than on muffs for extended periods and will allow the motor to truly come up to the idle operating temperature. It will also be quieter. After finished, drain tub via through-hull and put away.
pcrussell50 posted 06-26-2011 02:02 PM ET (US)
Great idea! I just ran her for 20 minutes on the muffs yesterday, and this time the telltale stream never did get warm.
-Peter
weekendwarrior posted 06-27-2011 09:48 PM ET (US)
The stream on many motors gets water before it goes through the cylinder/head and may not get warm or hot. The stream on my Honda for example gets cooler as soon as the thermostat opens, so the stream temp may not tell you what your motor temp is... depending on your motor.
Owtrayj25 posted 06-28-2011 08:37 AM ET (US)
Get a small portable tank and fill it with Avgas. Run this through if you are that concerned about jets gumming up. No ethanol in Avgas, and a healthy dose of lead....
BQUICK posted 06-28-2011 02:24 PM ET (US)
You will never get the oil over 212 deg that is needed to burn off the condensation that occurs when a cold engine is started. You are just adding moisture and acids to your oil unless you want to change your oil every time you run it......
More harm than good.

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Author	Topic: Four-cycle Engine Warm Up
pcrussell50	posted 06-15-2011 02:55 PM ET (US) Is [the procedure described below] an adequate warming for a Mercury 90-HP FOURSTROKE with carburetors? I haven't been able to use my boat for at least 3 weeks now, (though I start it on the muffs more or less weekly). I know and worry that merely starting it on the muffs for a few minutes is not enough to boil off any water condensation that has gotten into the crankcase. Well, yesterday, I hooked her up to the muffs, then got distracted with something else and forgot about it for at least 20 minutes. When I got back, the telltale stream was nicely warm, which I had never seen before, I suppose, because I had not let it run that long before. Do I have reason to believe that the oil got properly warm in this case? My performance cars and race car have oil temperature gauges. I look at them all the time. I wish there were a sender so I could add one to this motor, (maybe there is?) -Peter
Plotman	posted 06-15-2011 05:13 PM ET (US) I can't see why you feel the need to run a boat once a week on the muffs... And I can't see the value unless you let it get up to temp. If it's going to be more than about 2 months, then maybe either run it out of fuel or run it on a remote tank of stabilized fuel so you don't gum the carbs up. Other than that, I believe you can be too anal about an engine.
pcrussell50	posted 06-15-2011 05:28 PM ET (US) I'm in a unique situatuon... This motor is famous for having tiny little passages in the carbs that get gummed up easily. Further, it has a 12 gallon tank under the console. That amount of fuel takes me weeks to use up, since my outings are nearshore, and of short duration. Therefore, I always treat every tank with fuel stabilizer. If run her on the muffs long enough for the telltale stream to become toasty warm, (not burning hot), can I assume the oil got warm enough to evaporate the condensation? -Peter
Sixer	posted 06-15-2011 07:22 PM ET (US) Check the dipstick. No mention of your year, my 2007 EFI has one. The form of induction should not make a difference. The Merc SmartCraft gauge package might have the oil temp as an option in one of its data packs.
kwik_wurk	posted 06-15-2011 07:28 PM ET (US) Once a week, not needed. Flush it once after saltwater, and be done with it. (Once a month there after is more than sufficient, and before you head to the ramp.) What makes you think you have condensation in the block? Sounds like you need to find that source more than you need to run the engine once per week. Cold then warm water is expected once the thermostat opens up. Similar to a car, there is a bypass on the engine. So if you only flush a cold engine for a minute or two you aren't helping it much. In fact you're doing more harm than good; the startup and stop process is typically the most taxing thing on the engine. (Excluding stuff like running constantly at WOT, or with a dinged prop.) It takes 8 minutes on my 90 hp 2 stroke to get fully warm from a cold start. The telltale gets warm, but not hot warm. As long as the telltale is strong, and there isn't sputtering with vapor (steam) you should be fine.
Tohsgib	posted 06-16-2011 01:54 PM ET (US) NEVER WALK AWAY FROM A BOAT RUNNING ON MUFFS!!! If those muffs slipped off(which they do) you would have come back to a toasted engine after 20 minutes of no water. Run ringfree or run the engine out of gas but no need to run it weekly unless you are buzzed and have nothing better to do with your time....which I do every now and then.
zotcha	posted 06-16-2011 04:57 PM ET (US) Well your honest...and thats funny!
A2J15Sport	posted 06-16-2011 09:36 PM ET (US) It is far better to leave it OFF than running it a few minutes. Particularly with no load. Some of the carbed four strokes were extremely sensitive to fuel quality and expecially fuel varnishing. If is going to sit, for any extended period, treat the fuel. I treat my fuel all the time. No worries.
weekendwarrior	posted 06-21-2011 02:37 PM ET (US) Running once a week is fine and will ensure your carbs stay gum free. Idle speed will most likely not get the oil hot enough to steam off any fuel or water in the oil, but when flushing after salt use it is important to run it long enough for the thermostat to open, at least according to my Honda manual which says at least 15 minutes flushing after salt use.
weekendwarrior	posted 06-21-2011 02:40 PM ET (US) I will also add that you should never get water in the oil. If you do then you have an issue that needs to be addressed. You may get fuel build up in the oil from extended low speed running (some motors do and some don't), but in most cases cruising on plane for a while will get it hot enough to steam the fuel off.
pcrussell50	posted 06-21-2011 08:29 PM ET (US) Thanks, Warrior. Those were the tech-rich kind of responses I was looking for. Nick, I never thought of that. I'm nearly 3 years into boating, and I thought I knew it all. And you're a crackup, as usual. -Peter
Salmon Tub	posted 06-25-2011 11:44 AM ET (US) Get a large plastic tub/storage box and install a through-hull with a short hose. Running it in a tub of water is better than on muffs for extended periods and will allow the motor to truly come up to the idle operating temperature. It will also be quieter. After finished, drain tub via through-hull and put away.
pcrussell50	posted 06-26-2011 02:02 PM ET (US) Great idea! I just ran her for 20 minutes on the muffs yesterday, and this time the telltale stream never did get warm. -Peter
weekendwarrior	posted 06-27-2011 09:48 PM ET (US) The stream on many motors gets water before it goes through the cylinder/head and may not get warm or hot. The stream on my Honda for example gets cooler as soon as the thermostat opens, so the stream temp may not tell you what your motor temp is... depending on your motor.
Owtrayj25	posted 06-28-2011 08:37 AM ET (US) Get a small portable tank and fill it with Avgas. Run this through if you are that concerned about jets gumming up. No ethanol in Avgas, and a healthy dose of lead....
BQUICK	posted 06-28-2011 02:24 PM ET (US) You will never get the oil over 212 deg that is needed to burn off the condensation that occurs when a cold engine is started. You are just adding moisture and acids to your oil unless you want to change your oil every time you run it...... More harm than good.