One of my Suzuki DF50 2005 engines, with about 1000 hours on it, began emitting the overheat light when run over 5000 rpms. Shut down the engine, restart and run below 5000 rpm, everything is fine. Installed new thermostat. But no joy. Mechanic thinks corosion inside engine block, despite religious flushing after every use. He advised removing thermostats and running without them, as opposed to tearing into the engine to clean it out, which would be very expensive. Seems to have resolved the problem, at least for the time being. The increased flow of water without the restriction of a thermostat keeps the engine from overheating. He claims the engines will run just fine without a thermostat, but I'm wondering if there isn't a downside? Anybody had a similar problem?
Running without thermostats
- Thread starter Sealife
- Start date
Not had a similar problem but running without thermostats is generally a bad idea. If the engine has no thermostats it's possible that it will be "over cooled" and not get to the designed operating temperature. This sometimes happens when thermostats fail in the open position. If an engine is too cold all the time, certain components that are designed to have a tight fit at operating temperature (like the piston rings) will fit more loosely. The net result over time is excess fuel getting past the rings and diluting the oil. The engine can appear to be "making" oil in such a case and this is well documented in in some engines when thermostats fail in the open state. Running too cold can also cause carbon build up.
Almas Only
New member
You just can't believe how much oil can be "made" by running in high humidity at low rpm's without a thermostat, or with a thermostat that's failed in the open position. And, with the additives present in many high quality motor oils, the water doesn't slosh around waiting to be vaporized to the atmosphere when you run at higher rpm's. Instead, the water ends up being held in suspension with the oil itself by chemical bonds that are too strong to be broken by engine heat. Only after there is so much water that it can no longer be held in suspension by the additives will water show up separate from the oil, and by then, you've taken on more water than you might suspect. As an example, 4 qts. of Mobil 1 will hold about 1 quart of water in suspension.
Bottom line, find a new mechanic.
Bottom line, find a new mechanic.
Appreciate the replies, but consider this: with thermostat engine overheats at high rpms, but without runs ok. The thermostats, even open, restrict enough water flow to cause overheating due to buildup of deposits in water channels. By removing them, it allows enough additional flow to prevent overheat. Now I know this is only a stopgap, but the only other alternative I see is to tear down the engines to clean out the channels.....very expensive.
Also, I a m in So. Cal. where air and water temps are mild year round.
Also, I a m in So. Cal. where air and water temps are mild year round.
Assuming you have checked your water pump, and your engine is pissing a good streem.
If you trust your mechanics diagnosis, given the option of tearing the engine down and cleaning out the water jacket or trying to run the engine without the thermostat, I'll take the latter. The mechanic is obviously speaking from experience, what do you have to loose? You can't keep overheating your engine, that's not good. Pull the thermostat and see what happens. Monitor the temp, check the oil, listen for changes in how the engine sounds.
If the engine still continues to overheat than you'll need to diagnose further, if it seems to run OK than you'll just have to keep an eye on it.
Also, I'd find out what exactly the cost would be to fix it right.
Did you check the water intake? Could be restrictions there.
Take it one step at a time and either trust your mechanic or find a mechanic you can trust. I tend to saver the guy who's a little long in the tooth, the scrappy one who's been twisting wrenches on outboards for 20 or 30 years and doesn't give a c**p whether you believe him or not.
Keep use posted on how things go.
If you trust your mechanics diagnosis, given the option of tearing the engine down and cleaning out the water jacket or trying to run the engine without the thermostat, I'll take the latter. The mechanic is obviously speaking from experience, what do you have to loose? You can't keep overheating your engine, that's not good. Pull the thermostat and see what happens. Monitor the temp, check the oil, listen for changes in how the engine sounds.
If the engine still continues to overheat than you'll need to diagnose further, if it seems to run OK than you'll just have to keep an eye on it.
Also, I'd find out what exactly the cost would be to fix it right.
Did you check the water intake? Could be restrictions there.
Take it one step at a time and either trust your mechanic or find a mechanic you can trust. I tend to saver the guy who's a little long in the tooth, the scrappy one who's been twisting wrenches on outboards for 20 or 30 years and doesn't give a c**p whether you believe him or not.
Keep use posted on how things go.
Hi Mike;
Running without a thermostat, like everyone has said, is to be done only as the last resort. Our sea water temperature is 70-75 F these days, your engine will never reach 160-170 F., as required.
I would go on the following order:
1. Mix a 1:1 solution of "Salt Away" and let it sit for 24 hours. Rinse and repeat the procedure one more time.
2. Replace the entire water pump assembly, not just the impeller. Make sure the spline on the shaft and the water pump housing are in good condition.
3. Replace the thermostat, and while you are there, shine a light into the water jacket to verify the amount of visible corrosion.
4. Go for a ride and enjoy ...!!!
If you don't feel like doing all the work, take the boat to Eric Peterson at Specialty Marine (5th St. Oxnard), I have had good experiences with him.
Good Luck
Pedro
Running without a thermostat, like everyone has said, is to be done only as the last resort. Our sea water temperature is 70-75 F these days, your engine will never reach 160-170 F., as required.
I would go on the following order:
1. Mix a 1:1 solution of "Salt Away" and let it sit for 24 hours. Rinse and repeat the procedure one more time.
2. Replace the entire water pump assembly, not just the impeller. Make sure the spline on the shaft and the water pump housing are in good condition.
3. Replace the thermostat, and while you are there, shine a light into the water jacket to verify the amount of visible corrosion.
4. Go for a ride and enjoy ...!!!
If you don't feel like doing all the work, take the boat to Eric Peterson at Specialty Marine (5th St. Oxnard), I have had good experiences with him.
Good Luck
Pedro
Robert H. Wilkinson
New member
Perhaps not on topic but from another viewpoint(as an auto mechanic) I have seen cars run too hot after removing the thermostat because without the restriction coolant is pumped through the rad too fast to allow it time to cool.
With raw water cooling of coarse it is always cold water coming into the engine, but the above may apply on a boat with a closed cooling system.
Regards, Rob
With raw water cooling of coarse it is always cold water coming into the engine, but the above may apply on a boat with a closed cooling system.
Regards, Rob
Before going further into the issues, I would at least do what Pedro suggested. Cleaning engine passages does not necessarily require a tear down of the engine.
Rydlyme, white vinegar, or dilute hydrochloric acid are also good "salt" removers. The "salt" may also be a calcium carbonate salt, not just sodium or calcium chloride. You can run the engine, at an idle, with a 5 to 7 gallon bucket of water, with dilute acid. Watch the engine temp.
Have the engines been run in salt water without flushing? How did the passage near the thermostat look?
I bought a boat which had an overheat problem, and running it for some time at idle with dilute acid (like Rydlyme) solved the issue. It did not recur, since I flushed my engine after each salt water use (the exception being when cruising multiple days) Even then you can periodically put salt away solution thru the passages.
Try this before even considering tearing down the engine. Also get your cheap IR thermometer out and with the cowl off take spot readings on the engine block. Mark and chart the places you measured the temperature at. Then after flushing/running with the acid, re-measure the temps.
Right now, before you do anything, run both engines on the flusher (with the thermostat in), and measure the same places with the IR thermometer.
You are not going to run the engine at more than a fast idle, but you also want to know the temps at this speed, since the thermostat should open up during a fast idle.
Now a question--how often are you running the engine over 5,000 RPM?
I would take the boat out, and run up to the temp where the alarm is going off, (cowl off) and see what the temp readings are.) (don't shut down the engines, but drop to an idle--you want to keep cooling water flowing, even with an alarm--shutting down the engine does more harm.
Even the thermostat alone causes some restriction of water flow. That is why you are still getting alarms with the good thermostat in. So....not a good idea to run with no thermostat, do the impeller and housing,
Rydlyme, white vinegar, or dilute hydrochloric acid are also good "salt" removers. The "salt" may also be a calcium carbonate salt, not just sodium or calcium chloride. You can run the engine, at an idle, with a 5 to 7 gallon bucket of water, with dilute acid. Watch the engine temp.
Have the engines been run in salt water without flushing? How did the passage near the thermostat look?
I bought a boat which had an overheat problem, and running it for some time at idle with dilute acid (like Rydlyme) solved the issue. It did not recur, since I flushed my engine after each salt water use (the exception being when cruising multiple days) Even then you can periodically put salt away solution thru the passages.
Try this before even considering tearing down the engine. Also get your cheap IR thermometer out and with the cowl off take spot readings on the engine block. Mark and chart the places you measured the temperature at. Then after flushing/running with the acid, re-measure the temps.
Right now, before you do anything, run both engines on the flusher (with the thermostat in), and measure the same places with the IR thermometer.
You are not going to run the engine at more than a fast idle, but you also want to know the temps at this speed, since the thermostat should open up during a fast idle.
Now a question--how often are you running the engine over 5,000 RPM?
I would take the boat out, and run up to the temp where the alarm is going off, (cowl off) and see what the temp readings are.) (don't shut down the engines, but drop to an idle--you want to keep cooling water flowing, even with an alarm--shutting down the engine does more harm.
Even the thermostat alone causes some restriction of water flow. That is why you are still getting alarms with the good thermostat in. So....not a good idea to run with no thermostat, do the impeller and housing,
Discussion of vinegar treatment follows.
http://www.thehulltruth.com/boating-how ... negar.html
http://www.thehulltruth.com/boating-how ... negar.html
Well,here's the update. I did not feel comfortable running without a thermstat so I took it back to the mechanic and had him tear down the power head. Found lots of salt buildup. Paid $1500 and still happening. Mechanic tried everything he could think of....no joy. Few weeks later I took it to another very respected mechanic and this is what he found:
Internal anodes had never been checked or replaced and were virtually disintegrated.
First mechanic never checked the mid-housing where the pressure relief valve resides. It needed to be replaced, and first mechanic missed a lot of blockage areas.
Checked port engine and found the anodes to be in similar condition, so even though he feels it won't help appreciably, I bought 8 gallons of vinegar and a trash can, and he is going to run it all day tomorrow, monitoring it. Since this engine was not setting off the overheat alarm, I'm hoping this will help. Sooooo, starboard engine will cost me over 3K, and I might be facing another 1.5K for the port engine. :thdown
Internal anodes had never been checked or replaced and were virtually disintegrated.
First mechanic never checked the mid-housing where the pressure relief valve resides. It needed to be replaced, and first mechanic missed a lot of blockage areas.
Checked port engine and found the anodes to be in similar condition, so even though he feels it won't help appreciably, I bought 8 gallons of vinegar and a trash can, and he is going to run it all day tomorrow, monitoring it. Since this engine was not setting off the overheat alarm, I'm hoping this will help. Sooooo, starboard engine will cost me over 3K, and I might be facing another 1.5K for the port engine. :thdown
Marco Flamingo
Active member
I just bought cylinder anodes for my Yamaha F50. Some other mid-sized Yamaha outboards use the same ones (F40-F70 and maybe more). 8 anodes cost $49.95 because shipping for items #2 - 8 was only an additional two cents a piece. My dealer wanted about $20 each (not installed).
http://www.ebay.com/itm/Yamaha-20-250HP ... sI&vxp=mtr
Mark
http://www.ebay.com/itm/Yamaha-20-250HP ... sI&vxp=mtr
Mark
AstoriaDave
New member
Sealife wrote:
Checked port engine and found the anodes to be in similar condition, so even though he feels it won't help appreciably, I bought 8 gallons of vinegar and a trash can, and he is going to run it all day tomorrow, monitoring it. Since this engine was not setting off the overheat alarm, I'm hoping this will help.
Gallant effort, but vinegar is way too weak an acid to do anything. Stronger acids will attack the residue, but also the metal. The carbonates and more tractable oxides, especially of aluminum, are removed only within the first few hours after deposition. Saltaway and similar have therapeutic effects at their greatest within an hour or two of using the OB.
Checked port engine and found the anodes to be in similar condition, so even though he feels it won't help appreciably, I bought 8 gallons of vinegar and a trash can, and he is going to run it all day tomorrow, monitoring it. Since this engine was not setting off the overheat alarm, I'm hoping this will help.
Gallant effort, but vinegar is way too weak an acid to do anything. Stronger acids will attack the residue, but also the metal. The carbonates and more tractable oxides, especially of aluminum, are removed only within the first few hours after deposition. Saltaway and similar have therapeutic effects at their greatest within an hour or two of using the OB.
nordicstallion
New member
Hmmmm, more anode talk! I've got to get busy! Now,about that flushing. I've read somewhere about using dilute muriatic acid to clean out waterways with the salt eliminator/rabbit ear flush system. Any thoughts on that out there?
AstoriaDave
New member
Vern,
Muriatic acid, aka hydrochloric acid, aka stomach acid, is about 10,000 times more powerful than vinegar, aka acetic acid, in layman's terms. It will clean out the corrosion deposits, all right, and eat into the metals with equal vigor. Worse, the chloride in it makes it particularly effective in eating into ferrous metals and alloys.
No free lunch on this one, although sulfamic acid might be worth a shot. Common ingredient in agents designed to remove "iron" stains on bathtubs, shower stalls, and the like. Check the label on one before you try it.
Muriatic acid, aka hydrochloric acid, aka stomach acid, is about 10,000 times more powerful than vinegar, aka acetic acid, in layman's terms. It will clean out the corrosion deposits, all right, and eat into the metals with equal vigor. Worse, the chloride in it makes it particularly effective in eating into ferrous metals and alloys.
No free lunch on this one, although sulfamic acid might be worth a shot. Common ingredient in agents designed to remove "iron" stains on bathtubs, shower stalls, and the like. Check the label on one before you try it.
I just put "flushing AND salt" into the CBRATS search (click the search button in the logo tool bar) and Got more than 2 pages of hits, including:
Boat US Flushing article:
http://www.c-brats.com/viewtopic.php?t= ... shing+salt
Motor Flush (Salt Water)
http://www.c-brats.com/viewtopic.php?t= ... shing+salt
SaltAway, Did I get Snookered?
http://www.c-brats.com/viewtopic.php?t= ... shing+salt
SaltAway
http://www.c-brats.com/viewtopic.php?t= ... shing+salt
Flushing techniques
http://www.c-brats.com/viewtopic.php?t= ... shing+salt
Flushing out Salt deposits inside motors
http://www.c-brats.com/viewtopic.php?t= ... shing+salt
Superflush
http://www.c-brats.com/viewtopic.php?t= ... shing+salt
Which is not about a chemical at all.
Just to give you an idea of what's here already. And it is certainly OK to bring up new ideas and pursue them. Maybe the muratic acid has not been around already, so I new thread with that info would be good.
Sorry, guess maybe I'm being picky. Just thinking we are getting past the "Running without Thermastats" arena. AND I realize that these are related subjects so you are free and clear to ignore this post. :embarrased
My thought is that if someone were to be looking for flushing chemicals info it would be easier to find if it were in a condensed thread under a title along that line.
Harvey
SleepyC :moon
Dave,
Thanks for your very helpful, useful posts. Always technical info made understandable.
I was slow in getting mine in, and maybe should have just skipped it. I guess that is what the search thing is for, so that all those little hidden tidbits can be ferreted out.
Harvey
SleepyC :moon
Thanks for your very helpful, useful posts. Always technical info made understandable.
I was slow in getting mine in, and maybe should have just skipped it. I guess that is what the search thing is for, so that all those little hidden tidbits can be ferreted out.
Harvey
SleepyC :moon