Mercury Outboard Cooling System Service Interval

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Author Topic:   Mercury Outboard Cooling System Service Interval

boatman1979 posted 03-25-2010 05:32 PM ET (US)
I brought in my 150 Sport with Mercury 60-HP two-cycle engine for spring service today. The mechanic at the dealership asked if the water pump and thermostat had ever been replaced, to which I replied, "no." The boat is a 2004 model and the mechanic told me that I was very fortunate that those two components have not yet failed. He strongly recomended that I have them replaced before they become a problem.
Am I being persuaded into spending money on parts and service that I don't really need? I appreciate the feedback.
newt posted 03-25-2010 08:04 PM ET (US)
Not at all. Water pump and thermostats are regular maintainance items and should be replaced at six years. In fact, most people service the water pump every one to three years.
RevengeFamily posted 03-25-2010 08:10 PM ET (US)
Not a bad idea to have them done.
Worse case scenario is you overheat the engine and destroy it.
"Not so bad case" scenario is your out having fun with the family and the engine overheats. You find yourselves getting towed back the dock.
Lots of long faces and your out action in the middle of the boating season.

The thermostat and water pump are not difficult to change. Sometimes the lower unit hangs on tight but with some gentle persuasion, most guys can get the job done.
Hope this helps,
Norm
Jeff posted 03-25-2010 08:31 PM ET (US)
Was he being a little dramatic? Yes. Should these items be parts of regular maintenance? Yes. Yearly, or Bi-yearly? I wouldn't but, some do. Hours of service typically are seen as the main factor for change out before the age of the part.
While salt is different from freshwater use, I myself would expect no less than 5-6 seasons on either part. If you are keeping the boat on the trailer and flushing after every use, I bet you would find both to be in ok condition. If your motor has a strong tell tail stream and shows no over heating signs you "could" continue to run it. If you have the money and want piece of mind have it changed out. Though, I would not beat yourself up for running the motor as is up to now.
Both are items you could do yourself if at all handy with tools. I typically do them myself unless the boat is already in the shop for something else. Then I may have the mechanics do it and get some extra hours on the water instead of the driveway.
rtk posted 03-25-2010 08:33 PM ET (US)
It is not an unreasonable recommendation. Water pump replacement every three years or so is a typical service recommendation regardless if you run in salt or fresh water. Hours on the engine may dictate a shorter service interval than three years. Kind of like an oil change- 6 months or 5000 miles, whatever comes first.
The thermostat(s) replacement interval would depend on if you run in fresh or salt water. If you run in salt I would replace them more frequently than If I ran in fresh water. If the engine was run in fresh water it is not unreasonable to replace them after 6 years in my opinion as a regular maintenance procedure.
In a salt water environment I strongly feel it is a good practice to service these items on a fairly regular basis even though they are operating properly. Taking the nuts and bolts apart regularly will help avoid them seizing in the block or the housings.
Frozen bolts in a housing on a thermostat or water pump could turn a simple and relatively inexpensive repair into a very costly repair because of labor charges for extracting frozen bolts.
Rich
jimh posted 03-25-2010 08:44 PM ET (US)
Service on the water pump is usually needed when the water pressure decreases. There is anecdotal reporting that the rubber impellers used in Mercury engines need more frequent replacement than those used by other brands of outboard motor. Annual replacement is fairly common for some Mercury owners. However, not every outboard has its water pump overhauled annually. If my recall is correct I think a friend of mine ran his Yamaha V6 for over ten years without service on the water pump. When he finally had its impeller replaced it was working fine, and he just did it as a preventative measure.
The water pump has a rubber impeller, so there is some wear that occurs. The rate of wear depends on the rubber compound used and how clean and debris-free the pump housing is kept. Also operation that avoids ingesting sand, weeds, or other debris will help avoid damage to the impeller.
The thermostatic valves are other components in the cooling system that may need replacement, but I do not recall there being a standard interval. If the boat is run in saltwater there is always a greater possibility for corrosion in the cooling system. In freshwater operation, a thermostat could last a very long time.
boatman1979 posted 03-28-2010 02:04 PM ET (US)
Thanks everyone for your feedback. I really appreciate it and feel more comfortable about the service recomendation. With 450 saltwater hours over the past 6 years, I have decided to replace both components. I wish all of you smooth sailing in the upcoming season!
lakeman posted 03-30-2010 11:44 AM ET (US)
I will jump in here with my limited knowledge about Mercury Outboards cooling systems. The older small impeller should be changed about every one to two years; the newer motors with the larger impeller need a little less service. The thermostats need to be looked at, but not necessarily replaced. Now the older Optimax motors with the small impeller are very sensitive to heat, and may need the impeller changed each year--I know; I own one. Knowing this I still try to get by with every two years. One problem is that the rubber impeller mainly on the smaller ones take a set from setting too long with out use, like in winter. The set make them not efficient as they should be.
lurkynot posted 03-30-2010 08:44 PM ET (US)
I agree with [lakeman] regarding the Optimax impeller. [The water pressure indicated in PSI on a] 2001 Optimax 135 [appears to be] very sensitive [to the wear of or change in shape due to taking a set in the rubber impeller of the water pump]. I have gone two years [before changing the impeller in the water pump of a Mercury OptiMax 135-HP engine], but never longer than that. [The impeller in the water pump of my Mercury OptiMax 135-HP engine] needs to be replaced this year, as a matter of fact.
jimh posted 03-31-2010 10:46 PM ET (US)
For any outboard motor, the owner's manual should provide guidance on the recommended service interval for components of the motor such as the cooling system, and specifically the water pump.
As a point for comparison, I checked the owner's manual for my motor (which is not a Mercury motor). It specifies the following schedule in regard to the cooling system:
A ROUTINE INSPECTION should be made on the cooling system; check the water pump indicator; check water pressure.
Every 300 hours or every three years the water pump should be inspected and/or replaced; inspect and replace more often if water pressure loss or overheating occurs.
Bert Zwueste posted 04-01-2010 06:19 AM ET (US)
In the OMC manuals I believe that they used to explain that the impeller becomes less flexible over the years. The rubber takes a set. At low RPM the impeller has to sit relatively firmly against the inside of the housing of the pump to be able to pump sufficient volume of water to cool the engine. At high RPM the vanes of the impeller under the pressure of the water that it is pumping will contract and the volume that the pump displaces per revolution becomes less. Because of the high rpm however there is still enough or even more volume displaced when compared to the volume displaced at low RPM. When older impellers set they tend to remain in the position as if the engine is turning at higher revolutions. Consequently at low rpm the displaced volume is not high enough anymore and the engine overheats at low RPM. In extreme cases a rubber vane can even tear off and cause blockage in the cooling circuit.

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Author	Topic: Mercury Outboard Cooling System Service Interval
boatman1979	posted 03-25-2010 05:32 PM ET (US) I brought in my 150 Sport with Mercury 60-HP two-cycle engine for spring service today. The mechanic at the dealership asked if the water pump and thermostat had ever been replaced, to which I replied, "no." The boat is a 2004 model and the mechanic told me that I was very fortunate that those two components have not yet failed. He strongly recomended that I have them replaced before they become a problem. Am I being persuaded into spending money on parts and service that I don't really need? I appreciate the feedback.
newt	posted 03-25-2010 08:04 PM ET (US) Not at all. Water pump and thermostats are regular maintainance items and should be replaced at six years. In fact, most people service the water pump every one to three years.
RevengeFamily	posted 03-25-2010 08:10 PM ET (US) Not a bad idea to have them done. Worse case scenario is you overheat the engine and destroy it. "Not so bad case" scenario is your out having fun with the family and the engine overheats. You find yourselves getting towed back the dock. Lots of long faces and your out action in the middle of the boating season. The thermostat and water pump are not difficult to change. Sometimes the lower unit hangs on tight but with some gentle persuasion, most guys can get the job done. Hope this helps, Norm
Jeff	posted 03-25-2010 08:31 PM ET (US) Was he being a little dramatic? Yes. Should these items be parts of regular maintenance? Yes. Yearly, or Bi-yearly? I wouldn't but, some do. Hours of service typically are seen as the main factor for change out before the age of the part. While salt is different from freshwater use, I myself would expect no less than 5-6 seasons on either part. If you are keeping the boat on the trailer and flushing after every use, I bet you would find both to be in ok condition. If your motor has a strong tell tail stream and shows no over heating signs you "could" continue to run it. If you have the money and want piece of mind have it changed out. Though, I would not beat yourself up for running the motor as is up to now. Both are items you could do yourself if at all handy with tools. I typically do them myself unless the boat is already in the shop for something else. Then I may have the mechanics do it and get some extra hours on the water instead of the driveway.
rtk	posted 03-25-2010 08:33 PM ET (US) It is not an unreasonable recommendation. Water pump replacement every three years or so is a typical service recommendation regardless if you run in salt or fresh water. Hours on the engine may dictate a shorter service interval than three years. Kind of like an oil change- 6 months or 5000 miles, whatever comes first. The thermostat(s) replacement interval would depend on if you run in fresh or salt water. If you run in salt I would replace them more frequently than If I ran in fresh water. If the engine was run in fresh water it is not unreasonable to replace them after 6 years in my opinion as a regular maintenance procedure. In a salt water environment I strongly feel it is a good practice to service these items on a fairly regular basis even though they are operating properly. Taking the nuts and bolts apart regularly will help avoid them seizing in the block or the housings. Frozen bolts in a housing on a thermostat or water pump could turn a simple and relatively inexpensive repair into a very costly repair because of labor charges for extracting frozen bolts. Rich
jimh	posted 03-25-2010 08:44 PM ET (US) Service on the water pump is usually needed when the water pressure decreases. There is anecdotal reporting that the rubber impellers used in Mercury engines need more frequent replacement than those used by other brands of outboard motor. Annual replacement is fairly common for some Mercury owners. However, not every outboard has its water pump overhauled annually. If my recall is correct I think a friend of mine ran his Yamaha V6 for over ten years without service on the water pump. When he finally had its impeller replaced it was working fine, and he just did it as a preventative measure. The water pump has a rubber impeller, so there is some wear that occurs. The rate of wear depends on the rubber compound used and how clean and debris-free the pump housing is kept. Also operation that avoids ingesting sand, weeds, or other debris will help avoid damage to the impeller. The thermostatic valves are other components in the cooling system that may need replacement, but I do not recall there being a standard interval. If the boat is run in saltwater there is always a greater possibility for corrosion in the cooling system. In freshwater operation, a thermostat could last a very long time.
boatman1979	posted 03-28-2010 02:04 PM ET (US) Thanks everyone for your feedback. I really appreciate it and feel more comfortable about the service recomendation. With 450 saltwater hours over the past 6 years, I have decided to replace both components. I wish all of you smooth sailing in the upcoming season!
lakeman	posted 03-30-2010 11:44 AM ET (US) I will jump in here with my limited knowledge about Mercury Outboards cooling systems. The older small impeller should be changed about every one to two years; the newer motors with the larger impeller need a little less service. The thermostats need to be looked at, but not necessarily replaced. Now the older Optimax motors with the small impeller are very sensitive to heat, and may need the impeller changed each year--I know; I own one. Knowing this I still try to get by with every two years. One problem is that the rubber impeller mainly on the smaller ones take a set from setting too long with out use, like in winter. The set make them not efficient as they should be.
lurkynot	posted 03-30-2010 08:44 PM ET (US) I agree with [lakeman] regarding the Optimax impeller. [The water pressure indicated in PSI on a] 2001 Optimax 135 [appears to be] very sensitive [to the wear of or change in shape due to taking a set in the rubber impeller of the water pump]. I have gone two years [before changing the impeller in the water pump of a Mercury OptiMax 135-HP engine], but never longer than that. [The impeller in the water pump of my Mercury OptiMax 135-HP engine] needs to be replaced this year, as a matter of fact.
jimh	posted 03-31-2010 10:46 PM ET (US) For any outboard motor, the owner's manual should provide guidance on the recommended service interval for components of the motor such as the cooling system, and specifically the water pump. As a point for comparison, I checked the owner's manual for my motor (which is not a Mercury motor). It specifies the following schedule in regard to the cooling system: A ROUTINE INSPECTION should be made on the cooling system; check the water pump indicator; check water pressure. Every 300 hours or every three years the water pump should be inspected and/or replaced; inspect and replace more often if water pressure loss or overheating occurs.
Bert Zwueste	posted 04-01-2010 06:19 AM ET (US) In the OMC manuals I believe that they used to explain that the impeller becomes less flexible over the years. The rubber takes a set. At low RPM the impeller has to sit relatively firmly against the inside of the housing of the pump to be able to pump sufficient volume of water to cool the engine. At high RPM the vanes of the impeller under the pressure of the water that it is pumping will contract and the volume that the pump displaces per revolution becomes less. Because of the high rpm however there is still enough or even more volume displaced when compared to the volume displaced at low RPM. When older impellers set they tend to remain in the position as if the engine is turning at higher revolutions. Consequently at low rpm the displaced volume is not high enough anymore and the engine overheats at low RPM. In extreme cases a rubber vane can even tear off and cause blockage in the cooling circuit.