GypsyGene
Member
- Joined
- Jul 22, 2012
- Messages
- 6
- Location
- USA
- Vessel Name
- Mystic Gypsy
- Vessel Make
- 44' Island Gypsy (K&H)
I have twin Ford Lehman SP135's. The newly replaced impeller on the port engine has sheared completely. I have several questions, then I will add some details. Questions: 1) What causes impeller to shear? 2) Does it matter which direction the vanes are slanting at installation? 3) If it does matter which direction the vanes are slanting on installation, how to determine which is the correct direction?
Here's the story:
I motored from Long Beach, CA to San Diego. All systems operated perfectly. After 2.5 months in San Diego without running the engines, I cranked up and started heading out. Within about 2 miles, the alarm on the port engine sounded. The temp had reached 212. Shut it down and headed back to port. First Action: checked the pump; impeller looked ok, but replaced it anyway. Installed new impeller with vanes slanting the same direction as the old one. Second Action: called an old salty friend. He told me to check the seacock that feeds the port engine. Sure enough, it was encrusted with hard growth inside the seacock and in the intake recess beneath the screen on the wetted surface. Went under with diving gear and cleaned the intake. Inboard, cleaned the seacock with a screwdriver. It belched out hard growth then started to flow. Seacock lever operated smoothly. Third Action: Checked the raw water filter between the seacock and the pump. It looked clean, but opened it and flushed it out anyway. Re-assembled filter, hoses, etc. Headed out. Again, within 2 miles the port engine started overheating, but this time I was watching it and shut it down before the alarm sounded. Back to port. First Action: checked the flow coming out of the raw water filter, looked good. Checked the pump; discovered the impeller had sheared completely. Not a single vane was left intact. Since then I have talked with one mechanic who couldn't tell me what causes an impeller to shear, aside from old age. Also, he said it doesn't matter which direction the vanes are twisted on installation, it will correct itself. Also advised to lubricate the vanes with dish soap. The Jabsco replacement impeller kit comes with a supply of lubricant, which I used. As for the vane direction, the first time I mimicked the existing installation. But, now, the vanes are all missing, so I can't tell which is the correct direction. I'm assuming it would be the opposite of the flywheel direction, since the pump is geared directly to the flywheel. But, you all know what happens when we "assume."
Now that I am replacin the impeller for the second time, and I thought it would be wise to get some input beforehand. I hope there is someone on the forum who can advise me. Any advise will be appreciated.
Thanks for your interest.
GypsyGene
Here's the story:
I motored from Long Beach, CA to San Diego. All systems operated perfectly. After 2.5 months in San Diego without running the engines, I cranked up and started heading out. Within about 2 miles, the alarm on the port engine sounded. The temp had reached 212. Shut it down and headed back to port. First Action: checked the pump; impeller looked ok, but replaced it anyway. Installed new impeller with vanes slanting the same direction as the old one. Second Action: called an old salty friend. He told me to check the seacock that feeds the port engine. Sure enough, it was encrusted with hard growth inside the seacock and in the intake recess beneath the screen on the wetted surface. Went under with diving gear and cleaned the intake. Inboard, cleaned the seacock with a screwdriver. It belched out hard growth then started to flow. Seacock lever operated smoothly. Third Action: Checked the raw water filter between the seacock and the pump. It looked clean, but opened it and flushed it out anyway. Re-assembled filter, hoses, etc. Headed out. Again, within 2 miles the port engine started overheating, but this time I was watching it and shut it down before the alarm sounded. Back to port. First Action: checked the flow coming out of the raw water filter, looked good. Checked the pump; discovered the impeller had sheared completely. Not a single vane was left intact. Since then I have talked with one mechanic who couldn't tell me what causes an impeller to shear, aside from old age. Also, he said it doesn't matter which direction the vanes are twisted on installation, it will correct itself. Also advised to lubricate the vanes with dish soap. The Jabsco replacement impeller kit comes with a supply of lubricant, which I used. As for the vane direction, the first time I mimicked the existing installation. But, now, the vanes are all missing, so I can't tell which is the correct direction. I'm assuming it would be the opposite of the flywheel direction, since the pump is geared directly to the flywheel. But, you all know what happens when we "assume."
Now that I am replacin the impeller for the second time, and I thought it would be wise to get some input beforehand. I hope there is someone on the forum who can advise me. Any advise will be appreciated.
Thanks for your interest.
GypsyGene