overheated volvo penta 5.7GS , please help

[oneboat]

Hi everyone ,
i was yesterday on lake Ontario and while cruising at about 3500-4000 rpm the hose from raw waterpump to the engine got loose .
by the time i noticed the engine overheated . when i lifted the sunbed everything was smoke/steam and sounded like sparks ( there were no sparks but there was drips of water on exhaust manifold searing due to heat).
the starter got flooded for sure but the water didn't raised past the raw water pump level .

once evacuated the water with the bilge pump the engine was dead , called the c-tow which told me 1 hour and 45 minute to wait . on the temp gauge from the engine the gauge showed 250F , i don't know if that is the max or it was real.

after about 15 minute i tried to start the engine again and it started so i manage to get out of the water on my own.i wasn't very far and the engine temperature showed 175F like usual.didn't get very fast maybe 12-1500 rpm.

today i was studying the damage done and this is what i could see :
- gasket under the exhaust elbow is cooked - must change
- the two rubber hose connectors on the exhaust were cooked as well - must change
- paint on the exhaust pipe is bubbled up by heat - will scrape off and repaint

Assumed damages by me without opening -
- starter was flooded , now it works but will change it as it is unreliable
- raw water pump - i think should be fine as it has operated with water all the time
- recirculation pump - it was running without water - will replace that
- thermostat ?
- oil colour is clear , will change it as well with Sierra Sae 30

One more thing , today i started the engine on the trailer with water hooked up and the engine overheated at idle .
The engine sounds normal.

i don't see any other damages but i ask you guys if I should check / replace anything in addition to what i have already mentioned .

i also assume that the gasket from manifold to engine should be ok as this are design for higher temp anyway than the one between the manifold and exhaust elbow which was cooked.

Thank you

 

[oneboat]

i forgot to mention some details about the engine :
VP 5.7gsplkd '97 raw water cooled
boat is a Larson '97 bowrider .

 

[alldodge]

today i started the engine on the trailer with water hooked up and the engine overheated at idle .

Suggest a compression test because I think you blew a head gasket

 

[Scott Danforth]

250 is hot enough to warp the heads. time to do a lot of diagnostics

 

[tpenfield]

Sounds like you really overheated the engine . . . is there an overheat alarm on the engine?

 

[oneboat]

I have no overheat alarm . i plan to install one .

i tested again at idle and in fact works fine .i guess first time there was not enough water as i had another hose supplying water somewhere else.

should i replace the head gaskets as well?

from the look of them I would say head gasket look like cast iron.

 

[Lou C]

I had a similar problem back in 2013 and while the compression was ok and it ran ok I wound up with 2 blow head gaskets and cracked heads by the end on summer in 2016. You could roll the dice and run it or take the heads off and get them checked by a machine shop. Your call....

 

[alldodge]

i tested again at idle and in fact works fine .i guess first time there was not enough water as i had another hose supplying water somewhere else.

If the hose was not supplying enough water then need to check your impeller to see if it was damaged

should i replace the head gaskets as well?

I wouldn't unless compression test showed it needed it, or if it kept over heating and another cause was not found.

 

[oneboat]

OK, so i start removing some parts from exhaust . no surprises .
the gasket between the cylinder head and exhaust manifold was fine .
sparks looks pretty even . no rust on them just one i would say has a bit of oil on the thread , should i further investigate that?
i removed the valve cover and the cylinder heads block is cast iron and it was looking like new .
tomorrow will do the compression test .

i hope that will be even among the cylinders .

if it is even i would rather take the cylinder head in the off season unless the readings call for it now.
what would be consider normal for wet and dry reading on compression test?
thanks

 

[cnotecherry]

I would change your oil before you run it any more heat kills oil and I'm sure you don't want to do your internals as well synthetic might be ok but I wouldn't chance it

 

[alldodge]

Oil on a plugs thread could have come from the valve cover gasket, its a non-issue

New motor compression would be 150

 

[Lou C]

While the head gaskets may not have leaked as of yet, be on the look out for overheating and/or water in a cyl, or in the oil. If you decide to run it as I did, change the oil and do and oil analysis about 20 hrs after. See if water is showing up in the oil then. If so I'd fix it then because when a head gasket blows, you don't always get overheating (I didn't) it can show up as a reluctance to start, which can throw you off looking for normal starting issue causes but what it really is, water in the cyls causing the plugs to not fire. The issue here is that chronic presence of water in the cyl will corroded cyl walls, valve stems, etc.

When you do the comp test, use a remote starter switch and watch for water, even a mist of water, coming out of the cyls. Sure sign of a blown HG, or cracked head.

 

[oneboat]

I did the cylinder compression test today .
As i have removed the manifolds I did the test with COLD engine .
Results are like this
right bank
1 175
3 178
5 145 this is the lowest
7 180 this is the highest
left bank
2 180
4 170
6 160
8 170


I have tried with a bit of oil in cylinder 5 and it didn't do much , maybe 4-5psi .
Does these numbers sounds acceptable to you or I should open the cylinder head and check ?
If I do the math the lowest value is 80.5% from the largest number

Please advise .
Many thanks

 

[oneboat]

Thinking back to the oil on the spark thread , i think it is was number 5 cylinder .
The compression gauge was new , and i did the test twice to make sure measurements were consistent.
About 5 turning per cylinder .

 

[oneboat]

Thank you Lou C for your advise. will do a test for oil , in fact maybe 2-3 every 10-15 hours
As a practice I always check the oil color.
Will also redo the compression test at every 10-15 hours for 2-3 times to see if any changes .

 

[tpenfield]

I think your compression numbers are OK. The average is 170. The #5 cylinder is a bit low, but the rest are fine. You might want to do a cylinder leak test to see if there is a head gasket issue with #5.

 

[alldodge]

Agree with Ted

 

[Lou C]

I had the same thing. When mine overheated, the raw water hose from the transom popped off and filled the bilge with salt water and overheated it. I thought for sure the engine was a goner. I got it out of the water, hooked up the water hose and started it up. Ran fine, the comp numbers were good, just slightly lower than a few years before. Only damage I saw other than a lot of rust due to salt water spraying all over was 2 vaporized exhaust flappers. I pulled the drive and replaced the water tube grommets as they were blasted by the lack of cooling water (not shot but those have to be in good shape to seal well). Put it all back together, the exhaust system rubber hoses were not even scorched. I filled the exhaust manis with acetone to check for leaks because while I was waiting for a tow, I checked the temp of the exhaust manis after the overheat. Get this they were at 375*F!!! And NO leaks! So much for the "bad" OMC batwings! Put it all back together and it ran fine 2 more seasons, in '14, and '15. End of '16 both HGs blew. Found cracked heads, water in cyls (not in the ones with cracks ironically). So you may be OK, or may only get a few more years. Impossible to say for sure, comp tests and oil analyses can only tell you so much.

 

[oneboat]

update .
so i order some parts for the exhaust (the rubber couplers) which were scorched .
new gaskets for manifold and riser.
while i had the manifolds removed i put the manifolds and the riser in evaporust to clean up the rust inside the water jacket .
change the thermostat . put water temp alarm and oil pressure alarm .
Last weekend i run the engine in a weekend for 4 hours at about 3000 rpm
no water in the oil , i found 2 hair line cracks in the exhaust manifolds , about 2 inch long , .
i cant remember if they were there before or not , but for sure they leak a bit of water .
I plan to clean the crack and use some jb weld .

 

[Lou C]

Do not do that. If they are internally cracked where you can't see they will put water in your engine.,