Has anyone had a problem with the rubber sea water pump working fine at low speed, then failing at high speed? engine overheats at high speed, not a low rpms. A friend has suggested that the seawater pump impeller blades may be weak... looks good but at high speed may not handle the water volume. I've replaced thermostat, completely torn apart the heat exchanger, flushed raw water intake, checked anti freeze level. Boat has always been in freshwater. Any ideas?
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Have you checked the mixing elbow?
Jim: Have you checked the mixing elbow. Of course the impeller can be the problem and that should be checked first. The elbow is a common cause of overheating so give it a try too.
Jim: Have you checked the mixing elbow. Of course the impeller can be the problem and that should be checked first. The elbow is a common cause of overheating so give it a try too.
Archives
The elbow can clog up completely within three years, so that indeed could be the culprit. If the water isn't getting through the elbow, the impeller will self-destruct. Considerable and cogent research is available in the HOW archives. Type in "overheating" as the key search word and you'll have plenty to go by.
The elbow can clog up completely within three years, so that indeed could be the culprit. If the water isn't getting through the elbow, the impeller will self-destruct. Considerable and cogent research is available in the HOW archives. Type in "overheating" as the key search word and you'll have plenty to go by.
impeller
there was a batch of faulty impeller that were not working correctly and this may be your problem,try changing it anyway. they can sometime loose shape and not be as effective, it could also not be spinning on the seawater pump shaft at high speed.Impellers should be replaced every other year at the longest and removed from the pump for the lay up season so that it does not form to the inside of the pump. You should carry a extra one on board for a emergency back up. Good Luck!
there was a batch of faulty impeller that were not working correctly and this may be your problem,try changing it anyway. they can sometime loose shape and not be as effective, it could also not be spinning on the seawater pump shaft at high speed.Impellers should be replaced every other year at the longest and removed from the pump for the lay up season so that it does not form to the inside of the pump. You should carry a extra one on board for a emergency back up. Good Luck!
mixing elbow is fine-Yanmar3GMF
Thanks to all for quick replies I am going to order an impeller today. Mixing elbow is A-ok. Regards, Jim
Thanks to all for quick replies I am going to order an impeller today. Mixing elbow is A-ok. Regards, Jim
Jim, every weekend!
We do get to sail every weekend. You should also check out your hoses. Any hose that is on the suction side of the pump could be collapsing. Make sure that your anti-freeze mixture is 50/50 or less. Anti-freeze actually lessens waters ability to cool. Straight water mixture is the best for cooling but leaves your pump and water jackets more suceptible to corrosion and also lacks lubricant. For your area a mixture of 30-40% antifreeze is better, unless you need to worry about freezing. The mixing elbow does not seem to be much of a problem with boats that have been kept in fresh water. There is a chemical reaction with the salt water, diesel exhaust and heat all comming together in the elbow. I changed mine out not too long ago and it was also okay after 13 years.
We do get to sail every weekend. You should also check out your hoses. Any hose that is on the suction side of the pump could be collapsing. Make sure that your anti-freeze mixture is 50/50 or less. Anti-freeze actually lessens waters ability to cool. Straight water mixture is the best for cooling but leaves your pump and water jackets more suceptible to corrosion and also lacks lubricant. For your area a mixture of 30-40% antifreeze is better, unless you need to worry about freezing. The mixing elbow does not seem to be much of a problem with boats that have been kept in fresh water. There is a chemical reaction with the salt water, diesel exhaust and heat all comming together in the elbow. I changed mine out not too long ago and it was also okay after 13 years.
Embarassing conclusion to overheating
Intermittently, I would get a warning signal after engine had run at high speed for 5-15 minutes.. Having replaced everything.. the cleanest water system on the lake, I turned to the Yanmar 3GMF service manual.. It is a treasure of info.. With voltmeter in hand.. went to the instrument panel. 1. 3 out of 4 warning light sockets had lost their spring.. all bulbs good, but bad contact. 2. pressure and water temp in wrong sockets. 3. pressure switch had poor continuity..dirty connection at the switch where wire is screwed in. Boy do I feel stupid.. but now I understand that wiring harness diagram.. which fails to show all the connectors and is not always consistent about wire connection conventions.
Intermittently, I would get a warning signal after engine had run at high speed for 5-15 minutes.. Having replaced everything.. the cleanest water system on the lake, I turned to the Yanmar 3GMF service manual.. It is a treasure of info.. With voltmeter in hand.. went to the instrument panel. 1. 3 out of 4 warning light sockets had lost their spring.. all bulbs good, but bad contact. 2. pressure and water temp in wrong sockets. 3. pressure switch had poor continuity..dirty connection at the switch where wire is screwed in. Boy do I feel stupid.. but now I understand that wiring harness diagram.. which fails to show all the connectors and is not always consistent about wire connection conventions.
Dielectric Grease
Even though the electrical connections are older and no doubt have some corrosion already, I'd recommend some dielectric grease for them. Dielectric grease provides a moisture block and corrosion protection for all types of electrical connections. Application to terminals on bulbs is strongly recommended. This summer I replaced the running lights (one wire broke and the set screw was corroded) and one thing led to another. I used dielectric grease on the festoon bulb ends and covered all the metal parts. The primary purposes of the grease are to keep out moisture and prevent corrosion. Prevention of corrosion keeps the metal-to-metal contact point in a connector conducting electricity. For the long machine screws that hold the running light lenses on I used Lanocote, another good corrosion blocker material. I also used dielectric grease on all the Yanmar connectors I could find and also the shore power connectors. A Permatex link to dielectric grease is below. I got mine at NAPA and the newest Blue Sea catalog lists it. Enter "dielectric grease" in Google.com for more information. To reduce future maintenance and increase reliability, people with new boats should use dielectric grease, Lanocote and/or Never Seze on all appropriate connectors.
Even though the electrical connections are older and no doubt have some corrosion already, I'd recommend some dielectric grease for them. Dielectric grease provides a moisture block and corrosion protection for all types of electrical connections. Application to terminals on bulbs is strongly recommended. This summer I replaced the running lights (one wire broke and the set screw was corroded) and one thing led to another. I used dielectric grease on the festoon bulb ends and covered all the metal parts. The primary purposes of the grease are to keep out moisture and prevent corrosion. Prevention of corrosion keeps the metal-to-metal contact point in a connector conducting electricity. For the long machine screws that hold the running light lenses on I used Lanocote, another good corrosion blocker material. I also used dielectric grease on all the Yanmar connectors I could find and also the shore power connectors. A Permatex link to dielectric grease is below. I got mine at NAPA and the newest Blue Sea catalog lists it. Enter "dielectric grease" in Google.com for more information. To reduce future maintenance and increase reliability, people with new boats should use dielectric grease, Lanocote and/or Never Seze on all appropriate connectors.
Dielectric Grease - Part II
After looking at some of the internet hits on dielectric grease I came across this one on Ox-Gard which is very interesting. The article tells what dielectric grease does and doesn't do really well and it also gives a good discussion about when something like Ox-gard would be better, such as for use on crimp-on connectors or connections that aren't in close proximity to each other, such as the Yanmar block connectors.
After looking at some of the internet hits on dielectric grease I came across this one on Ox-Gard which is very interesting. The article tells what dielectric grease does and doesn't do really well and it also gives a good discussion about when something like Ox-gard would be better, such as for use on crimp-on connectors or connections that aren't in close proximity to each other, such as the Yanmar block connectors.
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