sea pump impeller question (Volvo 5.7)

[63A]

Before taking my boat (2000 Monterey 240/ 5.7 Volvo SX) out yesterday, I replaced the sea pump impeller. Pump was working fine but I had not replaced the impeller since I bought the boat a few months ago. Overall, very simple job. After replacing the impeller, put the muffs on the outdrive and turned on the water to force water into the pump. Then started engine to make sure all was workingproperly. So far, no problems. Approximately 2 hours later, I put the boat in the water at the lake. Engine started as normal but engine temp quickly rose past normal temp (approximately 165) and quickly went past 200 so I shut the engine down. After a few minutes to cool, I restarted the engine to maneuver back to the dock. Engine temp immediately started dropping and settled at 165. We decided to putt around close for a few minutes to watch the temp. Guage never went above 170. We decided to stay at the lake but watch the temp closely. Spent approx 6 hours on the lake, temp guage never went over 170. I don't know why the engine got hot initially- any suggestions?

[familyguy]

Good job keeping an eye on your temp gauge. Possibly you had some kind of obstruction blocking your water inlet on your outdrive (weeds/debris in the water) and that cleared from lack of suction at the inlet site when you shut down. Was your old impeller in okay shape when you pulled it? Vanes broken? If so, these can get lodged downstream of your impeller obstructing cooling water flow, ie narrow passages around your thermostat and cooling hoses that lead to the exhaust manifold.

[63A]

Old impeller looked great- no broken or cracked vanes- still very pliable. I kept the old impeller in the boat as a backup if the impeller goes while on the lake.

Everything is working fine now, just looking for an explanation to satisfy my curiousity.

[freelancer]

Old impeller looked great- no broken or cracked vanes- still very pliable. I kept the old impeller in the boat as a backup if the impeller goes while on the lake.

Everything is working fine now, just looking for an explanation to satisfy my curiousity.

63A, do you think maybe you lost the prime on the line between the time you had the muffs on and putting it into the water? I use to change the impeller weekly on an old Detroit 453 workboat and when I lost the prime I would have to boost the RPMs up to get enough suction for the water to flow through the pump and out the end of the boat. My problem was excessive air leaks that caused the system to drain out of the pump; hence I was going through many impellers. When you ran the engine at the dock, did you get underway and put a load on the engine or did you idle?

[Maclin]

You probably picked up some weeds or even a plastic sack that blocked the grates for a bit until it cleared. That would be my guess. We lost a towel one time and I figured that would make a nasty thing to get wrapped around a drive leg!

[mpancer]

Can u tell me or send info on how u replaced the impeller. Mine is due.
tx

[mikeneal]

I frequent poster here "DonS" has posted links to the factory manual, do a quickie search. Great resource and will tell you everythign you need to know.

Can u tell me or send info on how u replaced the impeller. Mine is due.
tx

[BILL INGRAHAM]

You Probably Picked Some Air And Eventually It Purged-i Tried Just An Impellar On An 800 Hour Vp 5.0 Gi And It Would Get The Risers Hot But Eng Temp Was Ok-all This On A Fwc System-these Bronze Pumps Loose There Tolerances-difficult To See-new Pump All Was Restored.