Impeller replacement

Roger K Sterling

Active Member
Oct 23, 2021
203
Boat Info
2000 Sea Ray 240 Sundancer
Engines
Mercruiser 5.0L, Bravo II, Thunderbolt V ignition
I had the outdrive submerged in a 30gallon container of water and I have the muffs on with garden hose running. No water was circulating and the engine temp Guage maxed out.

I'm about to replace the impeller which is mounted to the engine. I'm doing this because there is no water being drafted up through the out drive. Is the something else I should be investigating too.
 
How did you verify that there was no water making it to the engine? Did you remove the outlet hose at the sea water pump? Or maybe the inlet hose at the t-stat?

Has this boat seen a lot of salt water?
 
You need to pull out the impeller and account for all of the missing pieces. I recommend replacing the entire housing. When you start your engine make sure you have water flowing through the engine within a few seconds. Don’t wait for the engine to get hot. The impeller should be replaced every 2-3 years.
 
Hi everyone,
It was as most of you said, some scraped knuckles a bump on the head later and we go the sea water pump out. We replaced the impeller and now she's pumping water through the engine to the out-drive. I've uploaded a picture of the old impeller.
 

Attachments

  • 20220430_161211.jpg
    20220430_161211.jpg
    237.6 KB · Views: 233
Only what was saw inside the impeller housing. Any chance the rest get blown out?
 
Places to check... oil cooler (typically up/behind engine) and then the t-stat housing. After that, you're kind of out of luck as it's in the block.
 
Any missing parts will be stuck in the inlet side of whatever is immediately downstream of the pump.

If you can take that apart, great. If not you can blast bits out from the other end using water pressure from a garden hose.

Put a strainer made out of screen or a stocking on the outflow end to catch the parts so you can account for all of them.

You'll probably regret not doing this now.
 
Hi everyone,
It was as most of you said, some scraped knuckles a bump on the head later and we go the sea water pump out. We replaced the impeller and now she's pumping water through the engine to the out-drive. I've uploaded a picture of the old impeller.
A new impeller has 8 vanes……there are A LOT of missing pieces on your original. Not to beat a dead horse, but like everyone said, you need to back flush and get the broken pieces out of there.

Otherwise you could face random instances of overheating especially at higher cruise speeds, running cold when a pieces gets lodged in the thermostat, and possibly water pressure too high or too low depending on where debris gets stuck.
 
Is this what the impeller looked like before you removed it? Or did you do that damage removing it? If the former, ouch, and you need to chase down the missing pieces.
 
100% agree with the others in saying you need to find those other parts!! Follow the hose from the pump to the next thing in the water flow and take the hose off there. You might be able to use a wet-dry vacuum with a small flexible hose taped onto the end of the vacuum hose so you can push it in to "grab" some pieces that are trapped in there.

**Always** replace the impellers on a "new to you" boat unless you are 100% certain that they were recently done. Don't take the previous owners' word for it either. You should always carry a spare too, because even if YOU aren't able to change it, likely you could find something that could but you still need the part to be able to do it.

Bad impellers are probably the biggest cause of wasted or lost weekends when you could be enjoying your boat on the water!!
 
On that model engine the ps and fuel cooler are straight thru shots, so no trap there, I would look in the t-stat housing
 
Places to check... oil cooler (typically up/behind engine) and then the t-stat housing. After that, you're kind of out of luck as it's in the block.
Agree, unlikely to be in the oil cooler, but a large enough piece could get jammed. Easy enough to check, anyways.

If you're on a phone you may not be able to see his signature - he has a carb'd engine so (I know you know this - just mentioning it for Roger) there isn't a fuel cooler.
 
Thanks all, we're going to pull the hoses and go hunting for the impeller pieces to avoid overheating issues.

Question: should we be concerned about the thermostat. The Guage was briefly pinned and the alarm did go off which alerted us in the first place the impeller wasn't working. Could the brief over heat have dmaged the thermostat.
 
Thanks all, we're going to pull the hoses and go hunting for the impeller pieces to avoid overheating issues.

Question: should we be concerned about the thermostat. The Guage was briefly pinned and the alarm did go off which alerted us in the first place the impeller wasn't working. Could the brief over heat have dmaged the thermostat.
Unless you know different, It's 22 years old...
 
Many asked if we chase down the impeller pieces. The answer is - only in the housing unit. We unfortunately started the engine however the water-flo looked strong. We're are going to detached hoses and look for the other pieces.
 
If this hasn't been said already, this is a good demonstration of why you shouldn't wait for impellers to fail.

Replace them at regular intervals as preventative maintenance. I do mine every 2 to 3 years. They often come out looking pretty good and become emergency spares.
 

Forum statistics

Threads
112,950
Messages
1,422,861
Members
60,932
Latest member
juliediane
Back
Top