Volvo Penta 5.0 GL PWTR - severe overheat - thought I was on fire - troubleshooting Questions

[Augoose]

I haven't been around the forums in quite awhile as life became busy and the boat has been doing well over the last few years. Unfortunately for me I'm back following a bad overheating event last weekend and near fire on the water.
I did my summerization (fluids, impeller, outdrive, etc) last week and took the boat out this past weekend. Ran across the cove for about 4 mins at 3,000 rpms and after stopping, I noticed a bit of white smoke from the blower and engine compartment. Also a bit of white smoke beneath the swim platform on the surface of the water. Temp gauge read 130 (I know now the gauge failed), oil pressure was around 50 psi (idling). Smoke seemed to stop once the engine hatch was opened. Idled for a few minutes, smoke went away. Ran at about 2,000 rpms for another 30 seconds, smoke came back again. Headed back to ramp at about 3,000 rpms for about 3 mins and heard a popping and crackling sound from the engine and all of a sudden significant loss of power. Turned off the ignition, engine continued to sputter and almost diesel for a few seconds (which it never does).
Opened the engine hatch and white smoke poured out. Cut off the battery switch but the crackling sound continued which sounded like electrical popping. Went through 4 fire extinguishers thinking I had a fire, turns out there wasn't one thankfully. Dumped water all over the engine after extinguishers ran out out of fear of fire. Crackling stopped when we dumped water on the engine. Not a ton of water, a coffee can amount at a time. Temp gauge still read 130 through all of this and I didn't notice what the oil pressure was doing when I stopped the engine. Got towed in by a friendly fisherman.
Fast forward to getting home and inspecting the boat - the exhaust got so hot the outer coating of the elbow melted into some sort of hard plastic and had dripped down. The rubber coupler boot didn't appear to melt. Spark plug wires within a half inch of the pipe seem fine, as does the wiring harness. No melted insulation that I can see. The plastic threaded plugs which allow the manifolds to drain both melted and fell off. No heat damage to upholstery, rubber trim or fiberglass around the engine area. My exhaust manifolds are four years old, visually appear fine, and have only been in fresh water. In the winter I always drain the water from the block/manifolds and then pour in two gallons of marine antifreeze.
I ran a compression check tonight and shockingly I only had two cylinders which were low (one at 125, one at 134). The highest was 183 and the rest were in the 160's and 170's. This was on a cold engine of course. The boat is a '99 with around 400 hours and ran great previously.
Something must be wrong with the raw water flow - either the o-ring didn't seat well when I installed the new impeller (old impeller was intact), maybe the thermostat failed to open, or maybe I have some sore of blockage. I had accidentally left the outdrive at a 45 degree angle (not all the way up not all the way down) over the winter (in South Carolina) and a little water poured out from the prop when I summerized it. The boat is in a pole barn so it shouldn't have been rain water, but possibly some freeze damage occurred? I'll figure out why it wasn't cooling and I'm replacing the temp sending unit and gauge. Here are my questions:
1) What aspect of the engine was likely to suffer during the overheat? Warped head or failed head gasket?
2) If the head was warped or the head gasket failed, I'd assume I wouldn't even get the lowest compression reading of 125 and it would be unlikely to have such high readings on other cylinders?
3) When voltage is removed to a Faria temp gauge, does the needle settle all the way down? Mine is still reading 130.......
4) Could leaving the SX-M lower unit at a 45 degree angle allow sitting water to have frozen in the lower unit and caused damage?
I'm going to inspect and then replace the thermostat, the temp sending unit and temp gauge (it kills me to think I could have prevented this had the gauge been working), disconnect the water line feeding the thermostat housing and connect the muffs to the outdrive and ensure there's no blockage of water flow. If water pushes out to the thermostat housing, I was going to put everything back together and run the boat on muffs to see what happens?

I checked the oil level as it currently sits and its normal in appearance and at the correct level but I'd expect it to be if I wasn't pumping water when the overheating occurred. I assume after a test in the driveway, if the head gasket has failed I'll have milky oil?

Thoughts? Anything else you all suggest doing or checking before attempting to run it in the driveway?
Sorry for being so longwinded, just trying to be as detailed as possible.
Thanks
Augoose

 

[ESGWheel]

Oh boy, I feel for ya.
This engine was severely overheated > the white smoke I suspect was steam (did it have an odor?) and the crackling sound you assumed was electrical popping was instead the metal of the engine expanding.

While its good the motor turns over, I suspect your compression numbers will be a lot different once engine is warmed up (if it runs).

Prior to trying to run it:

• Investigate and solve the cooling issue. I would pull every hose off, the raw water pump (entire thing not just the cover), the circulation pump and t-stat. Anything that looks remotely suspect > replace.
• Also change the oil and filter. More difficult to do on a cold engine but do it. The temps your engine saw, even if the oil still looks good, could have easily cooked it.

To answer your questions:

1. Yes, warped or cracked head, hopefully only a ruined head gasket
2. Things may have sealed up when it cooled off
3. Unsure which way it should go, but clearly does not matter, its busted. Was it reading 130 at engine start? (see note 1).
4. I too have an SX and while anything possible I think that is not the issue but others with more experience on them may be able to comment.

More: post pulling off all the hoses look at best as you can in all the engine / exh passages and squeeze the hoses to listen for a crackling sound which indicates its needs replacement. Replace the impeller even if it looks good. Check the bearing and any potential degradation of the circ. pump (ie are the fins of the pump whole).

Note 1: I follow a protocol when doing a pre-start and then start. This includes reading all the gauges post starting to check oil pressure up, volts up and temp 'not up' if you will. And then while I am idling at the dock for a few minutes, I check again with particular attention to the temp gauge. Is it moving up as expected? Since I am docked, I generally have the engine running for 5 to 10 mins before getting underway giving me a good sense all is ok before I do. Not tying to be critical but these sorts of habits, once developed, can be a real life saver…

And I have to say: four extinguishers?! You are my kind of safety guy! I only have one but will now reconsider…

Please post how it goes and any other questions / help needed

Good Luck!

 

[Lou C]

I had something similar happen back in 2013, the cooling hose popped off right at the P/S cooler so the pump in the outdrive filled the bilge with seawater and the engine overheated of course. Seeing water coming in, but not knowing where it was coming in from, just couldn't see anything, I tried to get it to shore, the engine died about halfway there. Then as soon as the engine died, the water stopped coming in and I just waited till the tow boat guy came. Just for the heck of it I pulled out my IR temp gun and took some readings, exhaust manifolds (OMC V6 one piece units) 375*, engine block, 225-250*.... got back, pulled boat out of the water and started checking things....replaced the toasted flappers, and slightly toasted rubber exhaust hoses, but I was surprised that the paint didn't burn off the manifolds or aluminum exhaust pipes. I also split the drive and replaced the water tube grommets, these do get softened/distorted from an overheat and then you lose cooling water flow. Tested exhaust manifolds for leaks/cracks, none...
After all that started it up and....it sounded totally fine! No sign of water in the oil, so I warmed it up and did a compression test, normal for the V6, about 160-165. It ran fine for 2 more seasons, then at the end of the 3rd....
water in 2 cyls, symptoms were reluctant starting, rough running till warmed up, still a slight miss that it didn't have before....and water in the oil....salt water....
Got the boat out of the water, and came up with a way to test for bad head gaskets (compression test didn't show it) and they were for sure leaking water into the 2 cylinders. Took it apart, block deck looked good, took cyl heads to machine shop, they found both were cracked in the exhaust valve seat area of the center cyl of the V6 head. So, bought a set of reman 4.3 heads, and put it back together with Fel/Pro marine gaskets, ARP head bolts and did a 2 piece exhaust conversion at the same time (no more OMC batwings available) with Barr marine aftermarket and Volvo Penta exhaust parts (they just used OMC's stuff for years after the joint venture, same parts).
And it's been running fine, since I finished this in the spring of 2017.
Not saying you'll have the same outcome,
but it is common to have both blown head gaskets and cracked cyl heads from a bad overheat.

 

[dypcdiver]

I would be suspecting something wrong with the seawater pump, hoses on the wrong way or the classic extra 'O' ring.
To melt the plastic plugs in the manifolds there has been a serious lack of cooling water.

 

[Scott Danforth]

1) What aspect of the engine was likely to suffer during the overheat? Warped head or failed head gasket?
2) If the head was warped or the head gasket failed, I'd assume I wouldn't even get the lowest compression reading of 125 and it would be unlikely to have such high readings on other cylinders?
3) When voltage is removed to a Faria temp gauge, does the needle settle all the way down? Mine is still reading 130.......
4) Could leaving the SX-M lower unit at a 45 degree angle allow sitting water to have frozen in the lower unit and caused damage?

lack of cooling water is why you overheated. key off and anchor awaiting a tow would have been the best COA

when was the last time the raw water pump was serviced?

1- could have a thermally broken block or heads, could have taken out the bearings and collapsed the pistons. all the rubber bits in the exhaust are now burnt. head gasket is the least of the issued from an overheat.

2. your compression gauge is off, motor left the factory with 150 psi cranking pressure. adjusting the readings by 30psi, you have two readings at 100 psi and the others at 150. or you have water/oil/debris in the cylinders causing a higher reading.

3. no clue how the faria gauges are made. some gauge cores return on their own, some do not.

4. possibly, always leave the drive down, or better off, removed for winter.

it froze and snowed down here in Florida, so you did get freezing temperatures in south carolina.

replace your impeller

check the water supply fitting on the drive.

 

[Augoose]

Thanks to all for the responses.
The update is that I removed the impeller this evening and I inadvertently had two o-rings on the impeller pump housing. The housing is at the bottom of the engine where I can't see well and the o-ring itself sits inside a groove in the impeller base, altogether making it easy to accidentally double up. So that in addition to the failed temp gauge which kept reading 130 degrees spelled disaster for me. I was sucking air, melted the fins of the impeller closest to the impeller housing, and drew little to no raw water. I did run a garden hose from the raw water intake at the impeller housing and watched water flow nicely from the lower unit, so there was no obstruction. The water pump was replaced about 5 years ago to answer that question.
So my plan is to flush the coolant system to rid it of left over pieces of impeller, inspect all cooling hoses, replace the impeller, temp gauge, temp sending unit, and thermostat (its time anyway) and then run the boat on muffs to see if I get water mixing with oil. If that passes, I'll replace the rubber couplers in the exhaust system (they melted a bit) and then test the boat on the water. Time will tell I suppose. We'll see just how durable these GM blocks are.
Again thanks for all the help.

 

[Augoose]

Update - replaced the thermostat, thermostat housing, impeller, impeller o-ring and the circulation pump. Flushed the entire cooling system in driveway while components were removed. Took the boat to the ramp and sat in water for about 20 mins idling. Temp gauge slowly increased to 250 at which point it shot back down to 170, right as I felt cold water finally passing beyond the thermostat housing. I suspect I had a bubble at the temp sending unit as I could keep my hand on the sides of the exhaust manifolds while the gauge read 250 briefly. Tops of the exhaust manifolds were a bit hotter but nothing extreme. Launched boat and just circled at about 1,200 rpms for a few mins. Cooling water seemed to be circulating fine, could place hands on top of both manifolds at that point. Feeling good, put boat back on the trailer, shut down the engine and checked the oil - looked clean with no indication of oil mixing with water!!! I'm going to change the oil now since the old oil is probably toast from overheating and try running the boat on plane. Small steps and taking things one level at a time. Fingers crossed. Thanks to all for the help and advice.

 

[cyclops222]

This posting really points up how different boats are from a American car.

 

[Lou C]

Sounds good, one more thing that I replaced when I had a similar experience was the water tube grommets in the outdrive, these can melt slightly and distort and then you might not get 100% water flow when the boat is up on plane. The reason being that they are in the path of exhaust water and if you have an overheat and little water flowing, it will be all hot air which can melt rubber. It does require splitting the drive which can be difficult if it hasn't been done in a while.
If the engine runs well, at some point I'd check the sparkplugs for any sign of water and do an oil analysis toward the end of the season, you can have water in the oil and not see it if it is only a slight amount, but it likely will show up in the analysis.