Overheating after impeller change

[Henno]

Normal for one side to be hotter.

Next time you are in the water testing, put the engine at 100RPM. Remove the hose at the thermostat housing and output the water from that hose into a bucket for exactly 15 seconds. Should get around 2 gallons of water or so.

Many thanks for this Bruce. I will give this a try today hopefully.

 

[Henno]

Check the fitting at the drive where the raw water hose connects to the transom shield

Will try this today Scott, many thanks

 

[Henno]

If there were some impeller blades missing did you find them? If not then they may be lodged in the elbow that is warmer to the touch. If the power steering cooler is down stream from the raw water pump they may be inside the tube nest. Earlier Volvos had that style but yours may be the straight through type.
If there is a garden hose you can use try back flushing all the hoses.

Thanks Kenny. Will take a look today

 

[dypcdiver]

Mine did this last season, but only overheated at low revs. Anything over 2500rpm would run all day at 160F, at tick over she heated up really rapidly. Turned out to be a hole in the Bronze tube that joins the lower and upper parts of the outdrive, it sits in the exhaust tract. New ones are Stainless steel now.

 

[Henno]

UPDATE
So today I checked the manifolds and risers and the looked in very good condition with no rust build-up. Must have been changed at some stage by a previous owner and has been in fresh water since I got her.
I flushed out pretty much every area I could reach and then started her up. Again at idle it reaches around 170/180f but drops to around 160f when you give it some rev's.
Took the boat for a spin and it stayed steady at around 170. The more I opened the throttle the cooler she ran. After around 30 mins I took her back to the marina but again just as I was pulling up to the dock she crept up to almost 200F before I shut it down.
Still baffled how this boat is running much hotter straight after fitting a new impeller, than with an old impeller that was in bad shape.

 

[bruceb58]

The more I opened the throttle the cooler she ran.

That right there points to your impeller. At higher speeds, water is forced into the drive and the impeller blades flatten out so they are actually doing less. At low speeds where the impeller does more work, it is not pumping enough water.

 

[dypcdiver]

UPDATE
So today I checked the manifolds and risers and the looked in very good condition with no rust build-up. Must have been changed at some stage by a previous owner and has been in fresh water since I got her.
I flushed out pretty much every area I could reach and then started her up. Again at idle it reaches around 170/180f but drops to around 160f when you give it some rev's.
Took the boat for a spin and it stayed steady at around 170. The more I opened the throttle the cooler she ran. After around 30 mins I took her back to the marina but again just as I was pulling up to the dock she crept up to almost 200F before I shut it down.
Still baffled how this boat is running much hotter straight after fitting a new impeller, than with an old impeller that was in bad shape.

Sounds very familiar, see my post above.

 

[Henno]

Sounds very familiar, see my post above.

Thanks for this dypcdiver. Do you know if this is something I can check while the boat is in the water, or would it need to be lifted out?

 

[jhande]

Although those temps aren't too high I can understand the frustration.

This might sound silly but if all that was done was replace the impeller, could it be the wrong one?

 

[Broaders]

Sounds very familiar, see my post above.

Sorry dypcdiver , my emoji reply was due to a slip of the hand as I was picking up my dog, would not want to offend anyone.

 

[dypcdiver]

Thanks for this dypcdiver. Do you know if this is something I can check while the boat is in the water, or would it need to be lifted out?

I cannot think of any way to do it without lifting it out. BTW you have to remove the tube to inspect it, as in my case it was not visible until removed.
I lost most of a season's boating chasing down the problem, lifted the boat out 3 times, bought new pump etc. Let us know how you get on in this forum.

 

[Lou C]

Ok on the Volvo if any impeller blades came off they could be lodged anywhere between the impeller housing and the hoses for the manifolds. I would take off the thermostat housing remove the stat and check all the water passages make sure none are clogged. Install a new stat in the housing (it’s held in with a rubber ring). Reinstall the stat housing make sure all the hoses are clear.

 

[jbcurt00]

Sorry dypcdiver , my emoji reply was due to a slip of the hand as I was picking up my dog, would not want to offend anyone.

Check your PMs

If you re-hit the Like button, it should erase yout emoji error

 

[Vparzial]

I had this same issue with a Volvo Penta 3.0 motor. In my case, it was the seal on the water pump itself which had failed and was letting air in thus not getting good enough suction. I would disconnect the outlet on the water pump (On the motor side) and see if there is a good amount of water flowing through.

 

[Henno]

UPDATE
Thanks again for all the replies. So this morning I checked the water flow AFTER the pump. At idle I am getting around one gallon of water in 15 seconds. Is this normal or below average I wonder?
I am planning on replacing the impeller again this week with a new one, just in case there is some damage to it that I cannot see. Also the impeller I put in was not OEM so maybe that is making some difference.

 

[Henno]

Normal for one side to be hotter.

Next time you are in the water testing, put the engine at 100RPM. Remove the hose at the thermostat housing and output the water from that hose into a bucket for exactly 15 seconds. Should get around 2 gallons of water or so.

UPDATE
Thanks again for all the replies. So this morning I checked the water flow AFTER the pump. At idle I am getting around one gallon of water in 15 seconds. Is this normal or below average I wonder?
I am planning on replacing the impeller again this week with a new one, just in case there is some damage to it that I cannot see. Also the impeller I put in was not OEM so maybe that is making some difference.

 

[bruceb58]

UPDATE
Thanks again for all the replies. So this morning I checked the water flow AFTER the pump. At idle I am getting around one gallon of water in 15 seconds. Is this normal or below average I wonder?
I am planning on replacing the impeller again this week with a new one, just in case there is some damage to it that I cannot see. Also the impeller I put in was not OEM so maybe that is making some difference.

You should do it at 1000rpm but a gallon at idle sounds close.

I always use OEM

 

[ChrisCraftFan]

I'm with Lou C. I would have a look at the t-stat just to make sure. Normally I think impeller pieces would make it stick open and run cold but you never know what the little pieces of impeller will do if stuck in there.

 

[bruceb58]

I'm with Lou C. I would have a look at the t-stat just to make sure. Normally I think impeller pieces would make it stick open and run cold but you never know what the little pieces of impeller will do if stuck in there.

On my Volvo, output of the water pump went to the oil cooler first but mine was from 98 and it was a 7.4L

 

[Henno]

PROBLEM SOLVED!

First of all a big thanks to everyone who contributed to this thread. Today I finally found the problem after a day of drama and it turned out to be those missing impeller pieces.

Went for a spin on the boat and again ran fine when cruising along or at high speed. When I slowed up to idle the boat started to heat up, then spluttered and died. Eventually it started again after cooling down but not long after it happened again, smack bang in the middle of the shipping lane on one of the fastest flowing rivers in Europe (river Suir in Waterford, Ireland)

After frantically dropping anchor, I noticed when I turned on the ignition a whining noise from the fuel pump and it was quite hot to touch. One by one I checked the flow of water from the hoses around the thermostat housing and found pretty much no water flowing to the starboard side riser (the one that I mentioned before always ran hotter) and also no flow of water to the pipe leading to the fuel pump.

I took off the thermostat housing and the ports to the starboard riser, which also leads to the fuel pump, was completely blocked. I eventually pulled out 5 pieces of impeller rubber. Put back on the thermostat housing and pipes, turned the ignition and she fired back up and ran like a dream all the way home.

I probably should have found it sooner but I am just glad it looks like problem is solved.
Thanks again to all for the help.
Brian