Help! Volvo Penta 5.0 GXI-E Overheating

[Cristo36]

Hello All, First thank you all for the helpful suggestions you have provided throughout the years to assist with my tinkering.

My boat is over heating. 2005 Volvo Penta GXI-E 5.0. When I put it in the water or run on the muffs boat starts to over heat about the 12 minute mark. When I hook up the hose to the blue flush port boat operates fine!!! What am I missing??

Things I have replaced:

New Impeller
Rebuilt Raw water pump
New Thermastat
New Circulating pump

Things I have checked:
Impeller is still in good condition( Have checked after every new task)
Hose from drive to impeller is not blocked. holds pressure and flushed with water. ( From impeller hose down to drive. No luck getting water from muffs up to impeller.)

Real seems like I am not getting enough suction out the the impeller to get the water to the motor.

Any ideas would be helpful. The earliest appt is three weeks out for my local marine shop.

~Chris

I

 

[alldodge]

blue flush port boat operates fine!!! What am I missing??

I to want to know what is the blue flush port?
Post a pic

 

[Cristo36]

So reading some things on line it was refereed to as a " flush / washout" Blue cap on hose in left bottom corner

 

[alldodge]

Thanks, that's hat I thought but wanted to verify

I over heats in the water and on muffs but does not on the flush hose. Even though you stated

Hose from drive to impeller is not blocked. holds pressure and flushed with water. ( From impeller hose down to drive. No luck getting water from muffs up to impeller.)

There is still a blockage and if Scott Danforth would come along its probably the fitting on top the drive which brings water into the motor which gets restricted

https://www.marinepartseurope.com/en/volvo-penta-explodedview-7744400-26-6640.aspx

 

[Cristo36]

Fitting on top of the drive? I assume I'd have to pull my drive to access that?

 

[kmarine]

Most likely you have a piece of the old impeller stuck somewhere in the cooling system. The most common place is in the oil cooler, thermostat housing, sea water pump housing. Those are the most common ones. Afterward I recommend getting an infared thermometer gun and shoot the laser at different engine parts looking for hot spots. I bet you have blockage in the oil cooler restricting the amount of water getting to the engine.

 

[Cristo36]

The old impeller wasn't chewed up much. Maybe a piece the size of a corn kernel was missing from a fin but that's about it. I did think about the cooler as I tried to back flush down towards the drive from the flush port and the inlet impeller hose.

Maybe I can just replace the oil cooler about $225 bucks. What's the best way to get to that? Tucked along side of the block pretty tight

 

[kmarine]

just remove and flush you can see through it no need to replace. did you replace the thermostat on the top of the engine and clean out that hose yet. You can try running without the thermostat for a while also.

 

[kmarine]

You can also look for a pinched/cracked hose between outdrive and gimball housing

 

[jerryjerry05]

Remove the hose from the pump.
Tape the drive so no water gets out.
Then backflush and see if any water comes out anywhere on the drive???
No, then the transom connections and hoses are ok.

When I put it in the water or run on the muffs boat starts to over heat about the 12 minute mark​

The risers and manifolds, how old?

kmarine suggested a heat gun, good idea.

 

[Scott Danforth]

your system flow is as follows:
raw water inlet
raw water transfer hose
power steering cooler
raw water transfer hose
flush port
raw water pump
thermostat housing

your problem lies in either the raw water inlet, the raw water transfer hose and the fitting AD mentioned, or the power steering cooler.

the fitting the hose connects to on the drive is known issue. the old cast ones or the newer plastic ones..... all fail.....when you pull your drive for your annual inspection of the u-joints, bellows, etc. you also inspect that fitting. if the fitting is cracked or corroded, the system sucks air and you get no water.

you may need to back-flush the system because the first "strainer" in the system is the power steering cooler. anything that made it into the drive thru the inlet, however is just slightly smaller than the id of the tubes in the PS cooler will clog the PS cooler. if that is clogged, the system gets no water.

 

[lonewolf41]

Make sure you have the hoses hooked up to the raw water pump correctly. The fine folks that rebuilt mine hooked them up wrong and I had the same issue until I figured it out. If you pulled yours off for winterizing, make sure you connected them back correctly. Also, my oil cooler got damaged and had a flat spot on it where the inlet hose connected to it. It was just enough to let air into the system causing it to loose efficiency and overheat. I used the volvo procedure to diagnose the air leak.

Anyway, a couple of other things to check.

 

[jerryjerry05]

I thought I put this in the first reply.
Take the hose off the front of the manifold.
Take hose(water) and put in the hole.
Block it with a rag so no water escapes.
Turn it on full blast and see if there is any back pressure from the manifold.
The man/riser should flow as much water as you can get from the hose.
If it shows any back pressure then there's a blockage.

 

[Cristo36]

Had a few hours last night to work on the boat.

I have been able to pressure test and confirm no blockage in the cooling system.

I am not getting any suction from my impeller. I purchased a 10ft piece of hose and connected it to my raw water inlet and the other end into a 5 gallon bucket. No draw of water. Makes me think I don't have the right impeller. Is there any other reason that there would be no suction?

 

[alldodge]

Might not have the right impeller or your pump housing might have scoring inside

 

[Scott Danforth]

Had a few hours last night to work on the boat.

I have been able to pressure test and confirm no blockage in the cooling system.

I am not getting any suction from my impeller. I purchased a 10ft piece of hose and connected it to my raw water inlet and the other end into a 5 gallon bucket. No draw of water. Makes me think I don't have the right impeller. Is there any other reason that there would be no suction?

you wont get "suction"..... ever in a raw water pump.

raw water pumps only push fluid. they are not a positive displacement pump

at idle, the boat sits low enough in the water that the water level is about 8 inches higher than the pump to flood it and prime it. this is what allows the pump to move water when you first start your motor in the water.

as you speed up, the hydrodynamic force pushes water up the drive to the raw water pump, which then pushes it to the rest of the system.

if you tried to suck water up a hose from a bucket...... you toasted your impeller.

thats what muffs are for.

 

[jerryjerry05]

In the pump is the cam, it squeezes the blades and draws the water.
If the pumps had a lot of use and run in shallow water the cam can wear down and not work.
What condition is the inside of the pump?
ANY?? scoring? deep grooves anywhere? front plate any cuts, groves?
Remove the pump.
Try blowing through it as you turn the impeller, you shouldn't get any air through.

Prime the pump before running in a bucket.
A hose can push water to the pump.

 

[jfwalsh99]

This may sound pretty stupid, but I had the same problem awhile ago. Turned out to be a missing o-ring washer on the "flush / washout" Blue cap. The impeller was sucking air through the cap. Not enough water was entering the system, thus overheating the engine. Just a suggestion.

 

[Cristo36]

***** Update ******

After rebuilding my my entire cooling system and pulling my drive the problem was an after market impeller!!!

I installed a Sierra made impeller that I picked up from a local shop right after purchasing the boat. Had that installed while I was troubleshooting the boat about my "overheating problem". After exhausting every other possibility I ordered a Volvo OEM part. Instantly the problem was solved. Water circulation was great on the muffs and in the tub.

Took the boat out this weekend and she ran great.

Thanks for all the help guys.

~Chris

 

[alldodge]

I'm by no means a Sierra fan, don't use them my self, but even those work for a while. Good to know your all good again. I'm wondering if the parts store gave you the wrong one, there are many sizes