Volvo 5.7 Gxi running hot

Captain_CGC

Cadet
Joined
Aug 6, 2012
Messages
27
Hi

I have a 2003 Four Winns 268. I recently had a problem with the engine running hot, I shut it down and got a tow back to dry land.

I replaced the water pump and thermostat and backed the boat into the water and ran the engine with the boat on the trailer. Temp went up to 175 and maintained for 30 minutes. I launched and at idle within a minute of starting to motor the temperature went past 175 to 190, and I shut it down again and was towed back to dry land.

At the dock I removed the thermostat and was able to start the motor and limp onto the the trailer. The temperature did start to go down.

I removed the risers, they look pretty bad (rust), but I can blow through the water line and the sir seems to be flowing ok. Not that I have anything to compare it with. Boat used to be based at Chesapeake Bay.

My next step is replacing the risers, if that fails, what else can I do to identify the problem.

When running in land with a hose connected to the outdrive, the engine also runs steady and 175.

I'd appreciate any assistance.

Thank you,

Carlos.
 

cptbill

Senior Chief Petty Officer
Joined
Oct 6, 2012
Messages
732
Might be a dumb question but what temp. thermostat did you put in, witch water pump did you replace? and did you check the other one? and is the gauge accurate?
 

BRICH1260

Lieutenant
Joined
Jul 6, 2011
Messages
1,342
Probably need to state what type of cooling system you have, raw or closed system.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
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47,310
there are two pumps on the marine engines

the raw water pump, and the circulation pump

as cptbill asked, which pump did you replace?

also, have you checked for air bubbles? you could have a leaking raw water pump seal or a leaking supply hose fitting at the drive, both which would not show up when on the muffs.
 

Captain_CGC

Cadet
Joined
Aug 6, 2012
Messages
27
Hi

Thanks, it's RAW water. I replaced the RAW water pump, have not replaced circulation pump yet. I have a 150 degrees Thermostat.

I've checked for leaks, don't see any, not sure how to check for air bubbles.

I'm confident that the gauge is accurate, the high temp alarm did sound.

I removed the risers and they have a lot of corrosion, in fact 4 bolts snapped when I removed the risers.

I appreciate the help.

Regards,

Carlos.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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47,310
did the old impeller have vanes missing? if so, did you find them?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
47,310
so install a clear hose between the raw water pump and the thermostat housing and look for bubbles.
 

Saline Marina

Petty Officer 2nd Class
Joined
Sep 9, 2014
Messages
162
I'd take a look at the flex hose that sits in the area down behind where the bellows are and see if there is any sign of decay or external cracking in that.

While looking there, check out the metal-to-metal interface where the 6 studs are (those are seen under a plastic cover). But in that metal-to-metal interface there's a molded o-ring that follows a "worm track" (its not perfectly circular). If that interface leaks then it has a really good chance of sucking air. If there's corrosion at the interface especially from saltwater operation and there's flaking under the paint this could also be a sign of potential air leakage.

If you opened that interface (pulled the lower unit or "drive") to get at that o-ring, then there's a seal between the metal casting and the flex hose that I mentioned at the top.

Any of these 3 could cause a "broken straw" syndrome where there's plenty of suction but because there's an air leak in the fluid path, there is no (or minimal) lliquid raised up thru the suction pipe.

I used a little grey RTV on my drive in addition to the worm-tracked o-ring when I put it back as a "belt + suspenders" type of arrangement. It will probably need a little more scraping when I take it apart but I didn't want it to be a point of trouble in a ~20 year old stern drive.
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
11,803
If the 'risers' (actually elbows) were that bad...your exhaust manifolds are likely bad too, I'd count on replacing both...Barr Marine makes a nice aftermarket it for these that is about half the price of Volvo Penta OEM for the exhaust...These raw water cooling systems...need high volume of water IN and OUT...due to the fact that they are not pressurized...so anything that restricts the flow in, or adds air to the water...or restricts the flow out...is going to cause hot running....
 

Captain_CGC

Cadet
Joined
Aug 6, 2012
Messages
27
Thank you very much for all the replies. I've order a complete set of BARR exhaust manifolds and Risers. Will also check the intake side of RAW water for leaks. Would intake leaks cause overheating at idle speeds as well? I've read that intake leaks cause overheating at higher speeds. Does anyone have recommendations on flushing the water system, maybe I have an internal blockage. I have no doubt that the riser did restrict outflow, not sure to what extent. I'll give feedback once this is all done.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Hi
100% worth trying as AD says and bleeding the circ pump. This happened to two boats I’m aware of this year alone. You just need to have it running and quickly crack open the fitting on top of the circ pump. There is a small blank fitting there for taking a feed to a water heater or similar. Crack or loose first. Start engine and loosen it carefully. Likely you’ll get a spurt of air and water. All good after that, if it is.
 

Captain_CGC

Cadet
Joined
Aug 6, 2012
Messages
27
Thank you, I'll bleed the circles pump. I received the new risers and manifolds, will be installing this week. I hope this resolves the problem.
 
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