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

[Augoose]

Thanks all. I will look into the magnaflux service. I sprayed wd-40 over everything to keep the rust down while I wait on gaskets, so I suppose I'll need to get that cleaned off before testing.
Great point about the exhaust ports in the center.
My metal straight edge seemed to slide right across with no gaps, but .003" is really small. Thanks ESG for the links as well.
I did find one crack in a bolt hole - see red circle in image "head 2". Thoughts on that?

Also, the surface on both the block and heads between both center cylinders is more worn than other areas, so much that you can't make out the outline of what looks like a cylinder sleeve?

 

[ESGWheel]

Goose,
Once you decide on the level of cash you are willing to spend it will dictate what you do. Back in post #14 your concern was not dumping lots of $ into this boat. No issue with that whatsoever. This is why I was suggesting look for any obvious issues (like that crack) and if none go for it.

The more you inspect the more opportunity for spending $$. Assume you do the magnaflux and find cracks and the shop recommends not using that head. Are you going to get another head or does that bust the bank you are willing to spend? I’ll say it differently: if you do not know about the crack (that the shop would say is a no go) and you put it back together and get two more years out of it, good for you. Of course, the alternative is that it does become a problem.

So, the other side of the coin so to speak is this: are you willing to put your labor into it with minimum cash and if it does not work you are only out your labor so it’s OK. And heck you could still rebuild it properly from there. If go for it you are looking at only the cost of a set of gaskets and whatever was needed to be replaced due to the overheat. Note: use marine gaskets.

To be clear I am not advocating the short cut. I am just asking you to think thru this.

As an alternative to magnaflux that you can do yourself > dye penetrant. Here is the product (link) and a how-to video (link). Its nasty stuff so wear gloves.

For that crack. It is in the best spot possible > it does not intersect the combustion chamber, and it goes into the bolt hole. Note: when repairing cracks, the first step is to drill a hole at the end of it > this will help it from growing as the stress ‘warp arounds’ the hole and become less.

 

[Augoose]

Thanks. My plan is to sell the boat once it is repaired, proven reliable and running well as I'm already purchasing a new-to-me used boat. I will not pass on a problem to someone else, so I'm trying to choose from a few reasonable options to repair it.

Now that I found that crack, continuing on with that head probably isn't reasonable, but I wanted to get a 2nd opinion from the forum. And if I'm replacing one head, should I go ahead and do the other as well?

I'm not opposed to spending $1k or a bit more on two remanufactured heads to ensure the boat has several good years in front of it with a new owner. I won't put a new engine in it as the juice is not worth the squeeze.

I suppose I'll go forward with finding two replacement heads unless there's a different suggestion.

Thanks all!

 

[ESGWheel]

Good on ya for not wanting to pass along hidden issues. So, I would do this:

• Dye Pen the block > this way is stays in the boat (less cost) and provides a reasonable check for cracks. If found, post pics as It may be too detrimental to put on remain heads, ie now selling the boat with a busted motor.
• If block ok, do 2 remain heads and put back together. Have some fun and prior to selling do a compression test as a show of “all is good” to buyer.

Also suggest seeing what Lou and others think before taking any action.

 

[Lou C]

The advantage of having a machine shop checked the heads is that they will remove all the valves and that will reveal cracks you’d never see otherwise. My overheating happened in July of 2013, after this it ran perfectly normally you’d never know that there were cracks in both heads! I was seeing sodium in the oil analysis though even before the overheat. At that time before the overheat; I had seen the sodium & also wear metals (Fe & Al) starting to rise. So even before the overheat I think the HGs were starting to leak. Sodium in this case was from salt water cooling. After the overheat, still no sign of water in the oil. Then in Aug of ‘16, difficult starting and rough running, inspection revealed water in the oil and in 2 cylinders….
Since repairs were done in 2017 I’ve done 3 oil analyses and sodium has been on the typical range for marine engines and wear metals have come back down to normal.
Here's the Blackstone Labs reports going back to 2011...


Note: last report was done in 2024, this is when I changed from the regular Merc 25/40 oil to the Merc syn blend 25/50 oil, you can see that it definitely has more zinc and phosphorus than the conventional and holds its viscosity very well. 1242 PPM zinc is even more than just about all the diesel oils. Very expensive though but to me worth it. Remember the short block on this engine is original!

 

[Lou C]

PS here's what a reman head looks like (4.3 V6, pre-Vortec)...


I think what you're seeing is the residue of the old head gasket
Also in this pic you can see one advantage of the V6, none of the exhaust valves is right next to another, I guess it can run a bit cooler under high loads, than the V8.
It also points out another advantage of closed cooling, a pressurized cooling system maintains even temperatures better than un-pressurized open cooling (raw water cooling)....

 

[Augoose]

Opinions on quality of heads from Marine Engines 4 less? They seem to have good reviews online.

Aftermarket - https://marineengines4less.com/5-0l...er-volvo-penta-applications-years-1997-newer/

They don't offer a remanufactured option in 5.0, only 5.7.

 

[Augoose]

Alternatively Jegs offers remanufactured automotive heads - https://www.jegs.com/i/ATK-Engines/059/2CM2/10002/-1

I've read that the valves and springs for an automotive setup are not heavy enough and designed for the way marine motors are run - anyone have an opinion on this?

 

[Bondo]

Alternatively Jegs offers remanufactured automotive heads - https://www.jegs.com/i/ATK-Engines/059/2CM2/10002/-1

I've read that the valves and springs for an automotive setup are not heavy enough and designed for the way marine motors are run - anyone have an opinion on this?

Ayuh,.... Nothing "Marine" 'bout 'em,....
Same as heads used on pickup motors, which are the same as standard production automotive motors,....

 

[Augoose]

Ayuh,.... Nothing "Marine" 'bout 'em,....
Same as heads used on pickup motors, which are the same as standard production automotive motors,....

Perfect thank you sir. I'm leaning towards the remanufactured solution

 

[Scott Danforth]

the only difference between your boat motor and a truck motor is the head gasket, the core plugs, starter, the cam and the raw water pump. the ignition and induction were added by volvo along with the exhaust.

your "marine" flywheel is nothing more than a GM manual transmission flywheel.

the exact same short block and heads were pulled off the shelf as the pickemup truck motor going down the assembly line

fact. GM's Tonawanda engine plant made nearly all the boat motors for a year over a 2 day period, then went back to truck motors. that is how small the boat volume is to the truck volume.

later truck motors and industrial motors (your marine motor is an sub-set of the GM industrial motor line) used the same head gaskets and core plugs, so that minimized the changes

the truck motor cam is even really close to the boat motor cam.

 

[Augoose]

the only difference between your boat motor and a truck motor is the head gasket, the core plugs, starter, the cam and the raw water pump. the ignition and induction were added by volvo along with the exhaust....

Thanks Sir. I did order head gaskets based off the VP part number, so I should be good there.

Unfortunately the remanufactured heads from Jegs won't ship from the manufacturer until July 29th, so I'm not waiting for that. I can't find any other remanufactured options online so I'm inclined to go with Marine Engines 4 Less and purchase two of their aftermarket heads.

Thanks all

 

[Augoose]

Ok, here's the update. I finished installing new cylinder heads with all new gaskets on all associated components, new temp sending unit, new temp gauge, and a new 160 degree thermostat. I started the boat on muffs at idle and it sounds good. I bought an Amazon laser temp gauge and took readings for about 8-10 mins at the following locations (all fahrenheit) and at idle:
Thermostat housing - 132
Hose from Impeller to thermostat housing - 100
Hoses from thermostat housing to manifolds - 132/135
Impeller housing - 86
Top of left exhaust riser - 196
Side of left exhaust manifold- 220
Top of right exhaust riser- 193
Side of right exhaust manifold-195
Intake manifold near temp sending unit - 131
Top of temp sending unit - 132
Temp Gauge on dash read- 175
Left and right Exhaust elbows - 160

While idling on muffs, the engine felt hot but it might just be my paranoia. I kept waiting and waiting for the thermostat to open and cool down the exhaust risers and manifolds but it seemed that the thermostat never opened so I stopped the motor.
If the thermostat housing is still below 160, assuming the thermostat hasn't opened yet, is it typical for the manifolds and risers to be in the 220 degree range?
While I'm testing, what's the max temp I should let the exhaust risers and manifolds get to before shutting the motor off?
Thanks!

 

[Lou C]

I think your temps are normal except for the manifolds & elbows, I think thats higher than it should be…my Cobrs has the same Volvos style exhaust system and in the hose at idle runs about 95-100* for the manifolds & elbows. The only difference is the Cobra has the impeller
In the drive vs on the engine like the Volvo but I don’t think that should make a difference. How old is your impeller? Do your muffs fit well? Even on the water the hottest they get after running on plane is about 135-140* depending on where you take the reading.
Congrats on getting the job done!

 

[Augoose]

Thanks Lou. The impeller is new and the muffs fit very tightly. Three weeks ago when we tested the boat in the water (when head gaskets completely failed) the gauge on the dash appeared to show almost 210 before all of a sudden the engine temp dropped drastically down to 160 or so. At that time the risers and manifolds became cool to the touch. Its almost like this new Volvo Penta thermostat housing and thermostat respond super slow......
As I was writing this I pulled up the listing for my Faria gauge. To add to my confusion, this gauge is confusing to read. The red line indicts where my needle was earlier today at idle. I interpreted that to be around 210 Fahrenheit based on how close it was to what I thought was the "250" white tick. However, 80 degree Celsius is around 176 degrees Fahrenheit and 120 degrees Celsius is around 250 degrees Fahrenheit, so the two white ticks to the right and left of 80 don't correspond to 100 and 250 degrees Fahrenheit. Based on this assumption, if the needle were where the red line was it seems it would be about 185 degrees or so?
Regardless, it does seem my risers and manifolds were too hot.....if the engine was only getting to about 185 or so when I stopped the motor, why are the manifolds and risers getting so hot?

 

[Augoose]

Another update - I replaced my non-oem impeller with an OEM one and took it to the ramp. Temps never got above 175F and manifolds stayed cool.
Boat idled well at the dock so I meandered around for about 10 minutes at about 1,500 rpms. All was well until it wasn't......motor suddenly died. Started back up again fine and ran for about 30 seconds at which point the motor died again and wouldn't restart. Started paddling the boat back to the ramp and after about 7 minutes I started the boat again and it idled and ran at about 1,200 rpms. Got back to the dock and the motor died again when transitioning to reverse. Wouldn't start again.
Got it on the trailer and back home. Pulled the plugs right away and no indication of water that I could tell, but it certainly could have evaporated as it was about 30 mins after the motor quit that I got home and got the plugs out. Checked compression and the lowest was 175 and the highest was 195 with the new heads. Compression with the old heads had a lowest reading of 125 and a highest of 183 for comparison.
When I was adjusting timing during assembly, I got a slight shock while grabbing the top of the distributor. I've always heard conflicting explanations about getting shocked when grabbing the top of the cap- that its normal but that it also could indicate a crack in the distributor cap or a crack in the plug wires. My plug wires, rotor and distributor cap are 5 years old so I've ordered new ones. I ordered a new coil as well due to the overheat.
While the problem could be fuel related, I don't feel it is. I know carbs pretty well and I've been through this one for a cleaning last year, although I haven't yet looked down the throat to see if I'm getting fuel.
I'm happy with the status of the cooling and compression, but I'm worried about the cause of the motor stopping and that I might be getting water into the cylinders again. I suppose the next step is to install new plugs, wires, distributor cap, rotor and coil and see how it goes.
Should I put some clear hose between the thermostat housing and the manifolds to see if I'm getting bubbles in an effort to diagnose the condition of the heads and head gasket?
Would I see bubbles there or do I need clear hose feeding the circulation pump? Oil on dipstick still looks good with no smell or signs of water.
Thanks for the continued help and suggestions.

 

[ESGWheel]

Goose,
You need to buy a lottery ticket as your luck has to change!

I am catching up a bit. From your post no. 35:

At that time the risers and manifolds became cool to the touch. Its almost like this new Volvo Penta thermostat housing and thermostat respond super slow......

I am not the expert in on the water flow of these engines, but I believe your risers and manifolds are not fed by the t-stat, there is continuous water flow thru them regardless of it being open or closed. And if anything, once the t-stat opens, they would get warmer, not cooler since now flowing water thru the block and thus less cool water to the manifold / risers.

With the difference you are seeing with that new OEM impeller, I think we would all be interested in knowing the brand of the aftermarket one you were using. Please advise.

For the idea of getting shocked: there is no conflicting info about this IMO. If you are getting shocked the cap or wires are bad / going bad. These devices are designed with sufficient insulation properties for the voltage they handle. If new and still get shocked, then they are cheap / improper cap or wires. So yes, change them out.

For why the engine is cutting out, my money is on the ign components you are about to replace. However, you should still buy that lottery ticket along with the components

 

[Augoose]

Thanks ESGWheel, I keep hoping for some good luck! I suppose since my compression numbers are good the new heads are likely fine, so I need to stop worrying about water getting in and focus on the current symptoms. Had I not just put new heads on and had an overheat, I'd be focusing on spark at this point, and maybe fuel. Thanks for the confirmation about getting shocked by the distributor as well.
I'm embarrassed to say the impeller I had in there was an Amazon special by "SupremeMarine". When the overheat happened, it was an OEM impeller, but again I had two o-rings on at that time so that was my expensive mistake. Post overheat I was in testing mode and unfortunately went cheap on the impeller- get what you pay for I suppose.
And it makes sense about continuous water flow to the manifolds outside of the thermostat and while the engine is warming up - the manifolds would still need to be kept cool while the rest of the engine is getting up to temp.
Certainly appreciate hearing any other feedback, things to test, etc while I'm waiting on parts.

 

[Lou C]

Your cooling system is the same as what I have on the Cobra except for the impeller. It is a cool manifolds system in that the manifolds should be getting cool water the whole time the engine is running, even when the stat is closed. When the stat opens the manifolds will get a little warmer due to hot water exiting the engine via the manifolds. With a good impeller & non obstructed manifolds & elbows mine have always run from 95-100 at idle and the hottest they get is about 145 after coming off plane. If you are hotter than that there’s a problem either impeller worn, or rust clogged stat housing manifolds or elbows. About the running problem of you have that flat distributor cap replace it they are known to be troublesome. The old style standard caps were better! Check all connections on the coil and if you get a shocked when putting your hands on the top of the cap replace it & maybe the wires too!

 

[Lou C]

Thanks Lou. The impeller is new and the muffs fit very tightly. Three weeks ago when we tested the boat in the water (when head gaskets completely failed) the gauge on the dash appeared to show almost 210 before all of a sudden the engine temp dropped drastically down to 160 or so. At that time the risers and manifolds became cool to the touch. Its almost like this new Volvo Penta thermostat housing and thermostat respond super slow......
As I was writing this I pulled up the listing for my Faria gauge. To add to my confusion, this gauge is confusing to read. The red line indicts where my needle was earlier today at idle. I interpreted that to be around 210 Fahrenheit based on how close it was to what I thought was the "250" white tick. However, 80 degree Celsius is around 176 degrees Fahrenheit and 120 degrees Celsius is around 250 degrees Fahrenheit, so the two white ticks to the right and left of 80 don't correspond to 100 and 250 degrees Fahrenheit. Based on this assumption, if the needle were where the red line was it seems it would be about 185 degrees or so?
Regardless, it does seem my risers and manifolds were too hot.....if the engine was only getting to about 185 or so when I stopped the motor, why are the manifolds and risers getting so hot?


View attachment 408534

Yeah that’s def too hot. Mine shows 160 at idle might rise to 175 after coming off plane but any hotter and I start looking for problems