5.7 ltr Volvo Penta overheating issue

captmello

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Well, another overheating thread. 1988 Aq 260, 275 outdrive.

I had the boat on vacation and used it a few days with no problems. Day four it started getting hot at higher RPM but would drop down to normal (160 deg thermostat) very quickly at idle.

When I got home I began backflushing everything, knowing I had been in some shallow channels and had to have sucked up something. I had a fair amount of sand in the exhaust manifolds, so I hoped that would do it but no such luck.

I read a bunch of threads and decided to try the clear tube check. I replaced the two hoses from the thermostat housing to the manifolds and clamped the garden hose into the supply hose feeding the raw water pump.

Here is where it gets interesting if I haven't lost you already.

At Idle no bubbles but as the RPM's increase so do the bubbles. In past threads it sounds like the air would have to be coming in before the raw water pump, but I have the garden hose feeding directly (through the intake hose from the engine side of the power steering cooler) to the Pump.

Can someone please steer me in the next direction.

Thanks
 

Bondo

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Re: 5.7 ltr Volvo Penta overheating issue

Ayuh,...

Have you Changed in Impeller,..?? That's where I'd start....
 

captmello

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Re: 5.7 ltr Volvo Penta overheating issue

Have you Changed in Impeller,..?? That's where I'd start....

I changed the impeller a couple weeks ago. I pulled it out today and found that The "cam" inside the impeller housing is putting a bit of a nick in the center of the impeller wings. The old impeller i took out showed some similar wear. Could this be the problem and if so why is it damaging the impeller this way?? Would this cause the bubbling and air infiltration?

Thanks.
 

Bondo

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Re: 5.7 ltr Volvo Penta overheating issue

Ayuh,....

It might be time for a New Housing......

Unfortunately,....
I Don't do Volvos,+ have No Idea exactly what you're working on.....
Somebody with a Better grasp of your issue will be along,....
Good Luck....
 

captmello

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Re: 5.7 ltr Volvo Penta overheating issue

It might be time for a New Housing......

You're probably right about the housing but I've run out off boat funds for the year.

Can anyone confirm this would cause the bubbling. Where is the air coming in? At the housing itself?
 

Don S

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Re: 5.7 ltr Volvo Penta overheating issue

You can't do the bubble test on muffs, they will suck in a lot of air no matter what.
One thing you do need to look at is the hose connection on the outdrive. The end of the hose connection corrodes away inside the hose, and right where the hose ends. When a hole develops you have an air leak. In the water, it's under water when idling at low speed, but when you speed up it's out of the water and sucks air.
Give it a check.

PS: The water pump usually gets some marks on it from the cam, not a big deal.
 

jerryjerry05

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Re: 5.7 ltr Volvo Penta overheating issue

Look inside the pump for: grooves,grooves on wear plate(front cover),bad seal,wobbly shaft.If the inside looks good then the cam might be too worn down.
If you can post a pic of the pump.
Next the motor being that old might need the risers replaced. Take one side off and inspect the water exhaust ports on the end of the riser.
If the boat sets then you use it,possibly the corrosion and rust broke loose and clogged the risers. Jerry
 

captmello

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Re: 5.7 ltr Volvo Penta overheating issue

One thing you do need to look at is the hose connection on the outdrive. The end of the hose connection corrodes away inside the hose, and right where the hose ends.

You're right about the corrosion. The is a "V" shaped groove in in the bottom of the connection about a quarter inch deep. It hasent made it under the hose clamp yet.

I had previously had that hose off for some backflushing.

I'm not sure if this is a problem yet or not, However I did bypass the oudrive with the garden hose clamped directly into the raw water intake hose and got plenty of bubbles then too.

I put the boat in the water and used it quite a bit over the weekend. I ran it with the clear tubes for a bit and had the same progressive air bubbling. We tubed for hours at 2900RPM and never climbed over 160.


But the engine did start to climb to 190 when we running WOT for a few minutes.

Look inside the pump for: grooves,grooves on wear plate(front cover)

The cover seems ok along with the rest of the housing, however there does seem to be a little more play in the housing at the bearings than there should be, but I have anything to compare to. I can imagine you wouldn't want much play in any bearing arrangement. Do you think air could be leaking in there?

Take one side off and inspect the water exhaust ports on the end of the riser.

I took both risers off and tryed to snake them out with some wire but got nothing out. The manifolds and risers don't seem too corroded, whats the life expectancy in fresh water? I did replace the rubber hoses from the risers to the Y pipe this year.

At this point I'm not sure of my next move. I can see this going on for a while. I can start throwing parts at it but these aren't cheap. I may replace the raw water pump next spring. Something to look forward to.
 

captmello

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Re: 5.7 ltr Volvo Penta overheating issue

The more I think about the bubble test, It's hard to believe I wouldn't get air into the system when I'm going fast anyway. Does anyone think I could get air in around the raw water pump housing itself?

I get no bubbles at Idle, as soon as I raise the RPM's the bubbles just get worse, standing still or moving.
 

captmello

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Re: 5.7 ltr Volvo Penta overheating issue

Any advice for a first year boater.

Are Air bubbles in the system a normal thing? I know I'm leaking in air at my raw water pump. Do I eplace the whole pump or just the bearing and the seals.

Thanks
 

Don S

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Re: 5.7 ltr Volvo Penta overheating issue

You're right about the corrosion. The is a "V" shaped groove in in the bottom of the connection about a quarter inch deep. It hasent made it under the hose clamp yet

The wall of the hose connection is less than an 1/8" thick. Replace the hose connection, and the gasket and cure your problem. Or ask about it forever.
 

captmello

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Re: 5.7 ltr Volvo Penta overheating issue

Replace the hose connection, and the gasket and cure your problem.

I replaced the connection, the other one was pretty ugly. I had the boat out today with the clear hose on and did see a difference. However, I'm still getting a lot of bubbles at higher RPM's. The motor didn't get hot but I couldn't run at WOT with my wife in the boat (wimp) which is when it starts to get hot.

I've had some issues with the raw water pump in the past. It had a bad wobble when I first got the boat but I reinstalled it and it doesn't wobble any longer.

Could the pump be sucking air from around the bearings and seal?

Can you point me in the next direction. I'd love to fix this before the end of the season.

Thanks a lot.
 

captmello

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Re: 5.7 ltr Volvo Penta overheating issue

I was looking at raw water pumps. It looks like I can buy a whole assembly or parts. Not to cheap.
 

Don S

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Re: 5.7 ltr Volvo Penta overheating issue

Did you use a new gasket with your new hose connection on the drive? What was the condition of the hose itself? Was it clean inside the hose so it could seal proplerly on the new connector. Was the gasket surface clean and smooth? any corrosion on the H bracket that would prevent the new hose connection from sealing. How about the oring between the lower unit and the intermediate. If it's leaking air when on plane, well ...........................
 
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