Volvo Penta 5.7 gxi overheating

[bruceb58]

I looked back at one of your posts and see you have done this.

Have you tested your thermostat yet?

 

[Lou C]

I do agree based on what you say either the impeller isn’t pumping, or water is not getting to it, or the thermostat is stuck closed. If it overheats that fast there must be no water circulation at idle. Have you verified that the engine is actually overheating? You can use an IR temp gun to check the temp of the intake manifold right under the thermostat housing. That’s the spot I’ve found reflects the dash gauge most closely. When my gauge says 140 that spot is 135.
to answer the other questions for the plastic nipple the drive has to come off; for the water tube gaskets the drive has to come off and get taken apart.
which Volvo drive do you have? SX?

 

[ripjmk]

Just to answer the question you asked twice, Yes it is perfectly normal for water to come out below the bellows at idle. There is a gap in front of the exhaust bellows to allow idle exhaust and cooling water to escape to avoid the head pressure required to force it down and through the prop. When on plane the the prop hub creates a vacuum and sucks both the cooling water and exhaust gases through the drive and out the prop.

 

[Nitetymme]

OK, I agree, I really don't want to do this. Not many boat repair facilities in my area and the wait is super long. assuming I put it in water and pull the hose from the thermostat and no water comes out, what then?

 

[Nitetymme]

I do agree based on what you say either the impeller isn’t pumping, or water is not getting to it, or the thermostat is stuck closed. If it overheats that fast there must be no water circulation at idle. Have you verified that the engine is actually overheating? You can use an IR temp gun to check the temp of the intake manifold right under the thermostat housing. That’s the spot I’ve found reflects the dash gauge most closely. When my gauge says 140 that spot is 135.
to answer the other questions for the plastic nipple the drive has to come off; for the water tube gaskets the drive has to come off and get taken apart.
which Volvo drive do you have? SX?

The temp indicator rises to 210 degrees at which point the audible alarm sounds and the engine starts sputtering.

 

[Nitetymme]

What year and what specific drive do you have? Is it an SX or SX-A?
I would try to find a document titled “Volvo Penta Overheat Diagnosis”, it is a PDF that is right from V/P and gives all the trouble shooting steps needed to narrow down the problem. Have you checked the thermostat (removed it from the housing tested in a pot of hot water using a radiator thermometer), the standard stat opens at 160 and should be fully open at 175-180. The stat functions as a gate valve maintaining a set temp of 160-175 or so. If it does not open the engine will surely overheat.
The exhaust system functions as the exit for the hot water leaving the engine, if the cooling passages in the exhaust system clog with rust it will over heat. These open non pressurized systems depend on a large volume of cooling water in and out to keep the engine & exhaust at the proper temperatures.

Since attaching a water hose to the flush bib does not cause overheating condition, can we rule out thermostat?

 

[Nitetymme]

Make sure your blue cap flush port is tight and seating properly and has the O ring in it. If not, your pump will pull in air and you will lose the ability of the pump to pull in drive water. You might pull the impeller out and inspect it for damage due to the overheating.

Since replacing the impeller, I only ran at idle for approx. 5 minutes, long enough to see the temperature rose to 210..

 

[Nitetymme]

OK you have 2 bellows, the upper is the driveshaft bellows, there should never be water in that one, if there is it is cracked or torn and must be replaced, and you likely will have to replace the gimble bearing and maybe the u joints due to corrosion
The lower one, is the exhaust bellows, that is normal to have water inside, these don't really have to be replaced periodically but the upper one, as soon as you see small cracks in the folds, its time to replace it pre-emptively before it fails and costs you $$$. I've had them last 10 years but 5 is a safer interval. If you can store the boat with the drive level, the bellows tend to last longer than if the drive is left up.
There should be a V/P transom kit with the 2 o rings for the driveshaft and that odd shaped gasket that goes between the drive and transom mount. I use OMC gasket sealer on the 6 studs to keep the nuts from seizing up.

Other reasons why your impeller may not be picking up water:
1) there is a plastic water nipple in the transom mount (pivot housing is what I think they call it) if this cracks, due to improper winterization, it can suck air there
2) inside the drive there are 2 water tube grommets, if these are rotted, or burned from an overheat the impeller won't get enough water. There is a pipe that connects these 2 grommets, there was a member on here, who had the same problem, it turns out that there was a hole rotted in that pipe! But if he never split the drive he would have never found it. Once found, simple solution. For the water tube grommets the drive must be split (upper and lower gear housings) and it is really a job for a mechanic. I've done it on my Cobra just getting the bolts out and getting the upper gear housing off can be difficult. I have a trick for that problem though....salt water teaches you many tricks.

Now you have introduced another possible problem which I'm feeling reluctant to tackle. When you say I have to "split" the drive to get to the water tube, it's not sounding like I should tackle that problem. At that point I'd have to take to someone who will charge me twice as much to fix what I messed up!!! Are there directions on "splitting" the drive?

 

[bruceb58]

Now you have introduced another possible problem which I'm feeling reluctant to tackle. When you say I have to "split" the drive to get to the water tube, it's not sounding like I should tackle that problem. At that point I'd have to take to someone who will charge me twice as much to fix what I messed up!!! Are there directions on "splitting" the drive?

There is no way I would do that. If the drive is sitting in the water and idling the part could be completely cracked and it would never overheat.

 

[bruceb58]

Since attaching a water hose to the flush bib does not cause overheating condition, can we rule out thermostat?

Yes.

 

[Lou C]

Then go back to the last thing that was changed, the impeller.

 

[Nitetymme]

That would be the 3rd impeller replacement? The last time was a completely new pump assembly. Guess it's time to take it in.

 

[Nitetymme]

If the consensus is that I should NOT pull the out drive, then I will take it to a repair facility. To put my boat in the water is an hour drive one way.

 

[Lou C]

Ok now correct me if I missed something:
Not overheating till you replaced impeller
It will run on the flush hose and not overheat, this by passes the normal raw water intake system
You put it in the water it overheats
Correct?
So that leaves:
Impeller not pumping an adequate volume of water
or
Volume of raw water drawn in up the drive is inadequate
Have you hooked up water muffs to the drive and disconnected the hose going from the transom to the impeller housing @ the housing and checked for flow?
ever try to back flush that same hose the other way?
there is a p/s cooler on the back side of the engine that can get clogged if you ever sucked up mud or sand. I think the SX models have a clean out that can be removed while back flushing.
From what you report it appears to be either water supply to the impeller or the impeller itself.

 

[bruceb58]

Another thing...are you sure you have the two hoses going to the pump in the proper orientation which means the inlet is the inlet hose and the outlet is the outlet hose and they aren't swapped?

 

[Lou C]

Good point Bruce!

 

[Nitetymme]

Ok now correct me if I missed something:
Not overheating till you replaced impeller
It will run on the flush hose and not overheat, this by passes the normal raw water intake system
You put it in the water it overheats
Correct?
So that leaves:
Impeller not pumping an adequate volume of water
or
Volume of raw water drawn in up the drive is inadequate
Have you hooked up water muffs to the drive and disconnected the hose going from the transom to the impeller housing @ the housing and checked for flow?
ever try to back flush that same hose the other way?
there is a p/s cooler on the back side of the engine that can get clogged if you ever sucked up mud or sand. I think the SX models have a clean out that can be removed while back flushing.
From what you report it appears to be either water supply to the impeller or the impeller itself.

Over heating “was” the reason for replacing impeller. After replacing impeller it still overheated so I assumed pump housing was bad so I replaced the entire pump.

I put the drive in tub of water covering the intake and would not draft water. I assumed the water level needed to be at the level of the pump so I drove to the lake, still no cooling.

As stated before, attaching water hose, I had good back flow from water intake on drive. I removed hose to thermostat housing and had good flow with engine running. Good flow out of exhaust.

 

[Lou C]

Are you sure all the ports in your stat housing are open? Including the bypass?
PS the impeller will never pull water from a tub . The water level would have to be nearly up to the top of the drive. You need hydrostatic pressure to fill all the passages in the drive and the full length of that hose that goes to the stat housing. Are you sure about how the hoses are hooked up to the impeller housing?

 

[bruceb58]

If you put the drive in a tub and started it, you fried the impeller. Hopefully, it isn't the one you have in there now.

 

[Nitetymme]

Are you sure all the ports in your stat housing are open? Including the bypass?
PS the impeller will never pull water from a tub . The water level would have to be nearly up to the top of the drive. You need hydrostatic pressure to fill all the passages in the drive and the full length of that hose that goes to the stat housing. Are you sure about how the hoses are hooked up to the impeller housing?

Yes, the hoses that attach to the impeller housing are of two different sizes so impossible to make the wrong connection. I was wondering if the pump could draw water from a tub of water. OK, that was my mistake thinking it could.

I pulled the impeller and although it did not seem damaged, i measured it and it's diameter was 2 3/16". The diameter of the original impeller and also the new one I have replaced it with measure 2 5/16". Don't know if that makes a difference. Also, the reason I replaced the pump housing was I noticed the old one had slight grooves worn into it.

I visually checked the hose from the pump back to the drive pickup and have not detected any holes or cracks. I attached water hose to engine connection and water flows back out the drive pickup.

Now that I have a new impeller installed, detected no leaks in the system, what is the best way to test it? Will attaching flush attachment to outdrive do it or do I need to get it to the lake?