Overheating

[Chrisglastron]

I have a 2001 volvo penta 5.0 gl and have had intermittent overheating problems over the past ten years due to milfoil weeds in the lake I keep my boat. They get clogged up in the lower unit and I need a coat hanger to remove the clumps. So this year I was getting the boat started and noticed not a lot of water of water coming out of the lower unit hooked up to the muffs running. I touched the exhaust manifolds and they are hotter than normal. So I shut the motor off and disconnected the feed line to the impeller and turned on the hose noting good flow to the impeller and restarted the motor with no problems. I then started the motor the next day and same problem. I changed the impeller at the end of last season as well. So I changed the thermostat today and everything worked perfectly so I brought it to the lake. Sure enough same problem at the lake but I left it in the water hoping it would be easier to diagnose in the water. I did not have many tools with me but a flathead. So I took the feed hose to the thermostat housing from the impeller off and started the boat. No water coming out of the hose but there was water coming out of the thermostat housing. Where do I go from here?

 

[Lou C]

Re: Overheating

Sounds like you might have a problem similar to mine. I have an '88 OMC Cobra that is moored in salt water. I had a more or less chronic problem with barnacles growing in the lower unit water intake holes. OMC used an internal screen on these models to keep out eel grass and other stuff that could clog up the intakes, which we don't really have in my boating area, but barnacles are a chronic problem. The way I solved it was to split the upper and lower drive housings and clean out all the barnacles that had collected in there over the past 5 seasons. I also remove the internal screen since it was not really needed here and it is just a convenient place for barnacles to grow. Water flow is much better now. I will probably have to do this every 2 seasons. It sounds like you still have some of the debris in the water intake area of the lower unit. Try using a piece of thick wire like coat hanger wire bent at a right angle to rod out the holes and the area just above it. The Cobra and Volvo SX use a similar design in that respect but Volvo never used a screen, they have smaller but more holes.

 

[Chrisglastron]

Re: Overheating

But why is my problem intermittent is my biggest concern?

 

[Chrisglastron]

Re: Overheating

But why is my problem intermittent is my biggest concern?

Does anyone have any suggestion to troubleshoot my problem in the water?

 

[skydiveD30571]

Re: Overheating

Intermittent overheating problems are almost always due to impeller problems. You may have changed it last season, but it doesn't take long to ruin one...especially with occasional clogging of the inlet area. Also, just because the impeller looks good doesn't always mean it is functioning properly once it is under load and spinning.

 

[Chrisglastron]

Re: Overheating

Intermittent overheating problems are almost always due to impeller problems. You may have changed it last season, but it doesn't take long to ruin one...especially with occasional clogging of the inlet area. Also, just because the impeller looks good doesn't always mean it is functioning properly once it is under load and spinning.

I believe the problem is before the impeller but I want to diagnose. If I take off the water line coming from the lower unit at the impeller should there be water flowing or does the impeller create a vacuum for the lake cooling water? How do I test the impeller on the lake?

 

[skydiveD30571]

Re: Overheating

There will be some water flowing but only because the hose is lower than the water level. The impeller creates the suction that draws the water in through the lower unit and up to the raw water pump, then pushes it up to the thermostat housing. You can use clear hose from the raw water pump output to the thermostat housing, that way while running you can see if the impeller is drawing and expelling water or air.

 

[Don S]

Re: Overheating

Basically, if you have any kind of an overheating problem, the impeller is the first thing you look at. Volvo recommends you replace the impller yearly, that includes the oring on the cap. There is just too many things that can cause an impeller to fail, and it's easier to change than try to troubleshoot.
If your problem persists, then you go into troubleshooting mode.

 

[Chrisglastron]

Re: Overheating

Basically, if you have any kind of an overheating problem, the impeller is the first thing you look at. Volvo recommends you replace the impller yearly, that includes the oring on the cap. There is just too many things that can cause an impeller to fail, and it's easier to change than try to troubleshoot.
If your problem persists, then you go into troubleshooting mode.

I tried what the manual suggested as far as taking the hose from the impeller to the thermostat housing at the thermostat and holding it then start the motor and see if you get good flow 2 to 4 inches in the air. I didn't get any. So clearly I have a problem but I was hoping to test the for a clog first somehow before I take apart the impeller that I just changed when I winterized it.

 

[Don S]

Re: Overheating

If you are on muffs, it may take longer than 4 seconds to get water to the pump. even weak hose pressure.
I even had strong hose pressure one time, but because I used 100' of hose, it wouldn't pull water to the pump.
What manual are you reading anyway? Clymer? Seloc?

 

[Chrisglastron]

Re: Overheating

If you are on muffs, it may take longer than 4 seconds to get water to the pump. even weak hose pressure.
I even had strong hose pressure one time, but because I used 100' of hose, it wouldn't pull water to the pump.
What manual are you reading anyway? Clymer? Seloc?

Seloc manual.

 

[Don S]

Re: Overheating

Seloc manual.

Figures. Should have on the front (NOT Accurate in any way)

Go to this link VP.*/ 357328 and check out item #1.

 

[captkevin]

Re: Overheating

Was having a overheat issue last summer. Ended up have to replace the circulation pump. Parts guy at the marina took one look at the inside & said it was a river boat. Pump sucks sand right thru & it wears out casing.

 

[Chrisglastron]

Re: Overheating

Figures. Should have on the front (NOT Accurate in any way)

Go to this link VP.*/ 357328 and check out item #1.

I don't have those diagnostic tools. Went to the lake and there wasn't any water at the feed hose at the impeller, have to take the boat out and inspect for a clog before the impeller.

 

[Chrisglastron]

Re: Overheating

Went and got the boat yesterday and hooked it up to the muffs and I was getting inconsistent or lack of flow to the feed tube on the impeller housing. Several turns at reversing the flow and I managed to remove a couple sizeable clumps of weeds but didn't dramatically increase the flow. So I took of the house that connects to the transom and with the muffs I had good flow so then I unhooked the house on the backside of the oil cooler and it was just dripping. Is it possible to have a plug in the oil cooler? Does anyone have any pictures because I can only touch it but I can't see it. Any help would be appreciated. I took it all apart as we'll and found no other plugs and the impeller looked good. The housing was showing a little wear but it does have the plastic pressed in pieces, should I replace?

 

[Chrisglastron]

Re: Overheating

Went and got the boat yesterday and hooked it up to the muffs and I was getting inconsistent or lack of flow to the feed tube on the impeller housing. Several turns at reversing the flow and I managed to remove a couple sizeable clumps of weeds but didn't dramatically increase the flow. So I took of the house that connects to the transom and with the muffs I had good flow so then I unhooked the house on the backside of the oil cooler and it was just dripping. Is it possible to have a plug in the oil cooler? Does anyone have any pictures because I can only touch it but I can't see it. Any help would be appreciated. I took it all apart as we'll and found no other plugs and the impeller looked good. The housing was showing a little wear but it does have the plastic pressed in pieces, should I replace?

Wasn't the oil cooler hooked a hose up directly and water flowed good! Stupid question, I've tried everything so I thought maybe it could be the muffs, I moved them around slightly and squeezed them and the flow improved!