Alpha1 350 raw cooled boils and ticks rapidly after short time on muffs

[Lou C]

those dry joints can have both ports open, both closed (for closed cooled manifolds) or one closed and one open.

 

[QBhoy]

Thinking similar to some others. You may have the wrong gaskets or set up in the riser to manifolds. But I’d also always thought a 140 t stat is for closed cooling engines. 160 is for raw.
I once had to bleed air out the circ pump housing on an engine to get water around it. Afterwards found out it was drawing air in from the cooler that’s fitted on the intake line between outdrive and engine. That was a different set up to yours though.

 

[Lou C]

Thinking similar to some others. You may have the wrong gaskets or set up in the riser to manifolds. But I’d also always thought a 140 t stat is for closed cooling engines. 160 is for raw.
I once had to bleed air out the circ pump housing on an engine to get water around it. Afterwards found out it was drawing air in from the cooler that’s fitted on the intake line between outdrive and engine. That was a different set up to yours though.

Other way round with the 'stats. 140 for raw water 160 for closed cooling. Just about all OMCs and Volvos came with 160s regardless without an option for a 140 as Merc does and I was able to find a 140 for a BB Chevy Volvo application last spring and tried that but the engine really ran too cool esp at idle, so I went back to the 160. When I had the head off to replace them 4 years back I didn't find any salt build up to speak of despite running a 160 stat in salt water for years.
The idea behind the lower temp stat in salt or raw water cooling is that the calcium deposits are though to drop out of suspension at temps approacing 160 or so, hence the 140 stat. Outboards do that as well.

 

[QBhoy]

Other way round with the 'stats. 140 for raw water 160 for closed cooling. Just about all OMCs and Volvos came with 160s regardless without an option for a 140 as Merc does and I was able to find a 140 for a BB Chevy Volvo application last spring and tried that but the engine really ran too cool esp at idle, so I went back to the 160. When I had the head off to replace them 4 years back I didn't find any salt build up to speak of despite running a 160 stat in salt water for years.
The idea behind the lower temp stat in salt or raw water cooling is that the calcium deposits are though to drop out of suspension at temps approacing 160 or so, hence the 140 stat. Outboards do that as well.

Hi Lou. Wouldn’t normally question a guy like yourself and with your knowledge…but are you sure about this ? Any of my GM raw water t stats have all been 160. The few closed cooling I’ve known were 140 I’m sure. You’ve got me doubting myself here. I’ll need to double check. Haha.

 

[Lou C]

No worries but I know for sure that Merc used to specify 140 for raw water and 160 for closed. In fact my brother has a 2020 Chaparral with a Merc 4.5 V6, raw water cooled and it has a 140 and that thing runs really cool. OMC and Volvo used 160s in nearly all of there models with a few exceptions for Volvo. When you have closed cooling with a pressurized cooling system you can allow the engine to run hotter (160-180 or so) because the pressurization factor keeps the coolant from boiling till a much higher temp. So it is better for engine life and efficiency for it to run closer to what GM designed it for (the small blocks in most auto applictions had 195* stats and ran at about 200*). With a raw water system that is unpressurized you have a couple of things working against you, one being the build up of corrosion that reduces heat transfer and the other, you can get localized boiling in the hottest parts of the cooling system (usually in the cyl head around the exhaust valve seats) even if the temp gauge doesn't register over 200 because the area where the temp sending unit is (in the intake manifold) doesn't get as hot. That's also why if you have an audio alarm for overheating on a raw water cooling engine its set to go off at 200 usually. Whereas the same engine in an auto application with the pressurized cooling system can go to 200 as a normal thing.

 

[QBhoy]

No worries but I know for sure that Merc used to specify 140 for raw water and 160 for closed. In fact my brother has a 2020 Chaparral with a Merc 4.5 V6, raw water cooled and it has a 140 and that thing runs really cool. OMC and Volvo used 160s in nearly all of there models with a few exceptions for Volvo. When you have closed cooling with a pressurized cooling system you can allow the engine to run hotter (160-180 or so) because the pressurization factor keeps the coolant from boiling till a much higher temp. So it is better for engine life and efficiency for it to run closer to what GM designed it for (the small blocks in most auto applictions had 195* stats and ran at about 200*). With a raw water system that is unpressurized you have a couple of things working against you, one being the build up of corrosion that reduces heat transfer and the other, you can get localized boiling in the hottest parts of the cooling system (usually in the cyl head around the exhaust valve seats) even if the temp gauge doesn't register over 200 because the area where the temp sending unit is (in the intake manifold) doesn't get as hot. That's also why if you have an audio alarm for overheating on a raw water cooling engine its set to go off at 200 usually. Whereas the same engine in an auto application with the pressurized cooling system can go to 200 as a normal thing.

Lou. Definitely agree and understand the idea around a closed and pressurised system being able to run hotter (with water boiling above 100 degrees C if under pressure). Although I have owned and maintained my own petrol powered boats with gm over the years…I professionally worked on diesels for a living. All had closed cooling, as you can imagine.
That’s what made the idea of a lower temp t stat for closed cooling on these, stand out and stick in my memory. Was very surprised by it. I’m still almost certain all the GM engines I’ve owned (all raw water) have been 160 t stats. If it’s otherwise elsewhere, I can only think that the difference may be as a result of cold waters where I live. Not sure. But I’d almost bet if you looked up your average GM 5.7 raw water cooled engine and searched for a t stat…it might suggest a 160 part. Certainly I’d think it does here in Europe at least.

 

[QBhoy]

No worries but I know for sure that Merc used to specify 140 for raw water and 160 for closed. In fact my brother has a 2020 Chaparral with a Merc 4.5 V6, raw water cooled and it has a 140 and that thing runs really cool. OMC and Volvo used 160s in nearly all of there models with a few exceptions for Volvo. When you have closed cooling with a pressurized cooling system you can allow the engine to run hotter (160-180 or so) because the pressurization factor keeps the coolant from boiling till a much higher temp. So it is better for engine life and efficiency for it to run closer to what GM designed it for (the small blocks in most auto applictions had 195* stats and ran at about 200*). With a raw water system that is unpressurized you have a couple of things working against you, one being the build up of corrosion that reduces heat transfer and the other, you can get localized boiling in the hottest parts of the cooling system (usually in the cyl head around the exhaust valve seats) even if the temp gauge doesn't register over 200 because the area where the temp sending unit is (in the intake manifold) doesn't get as hot. That's also why if you have an audio alarm for overheating on a raw water cooling engine its set to go off at 200 usually. Whereas the same engine in an auto application with the pressurized cooling system can go to 200 as a normal thing.

Looks like some early early raw water might be 140. Searched through a few pages on google there and came across the suggestion. But certainly over here. All of these raw water cooled spec a 160 after 1987 at least. Closed cooling spec 140. Weird for sure…but seems to be the case.

 

[Scott06]

Looks like some early early raw water might be 140. Searched through a few pages on google there and came across the suggestion. But certainly over here. All of these raw water cooled spec a 160 after 1987 at least. Closed cooling spec 140. Weird for sure…but seems to be the case.

Agreed my 04 had as OEM a 160 stat for raw water cooled

 

[QBhoy]

Agreed my 04 had as OEM a 160 stat for raw water cooled

I’d say most do that I know of. I know for sure my ‘03 v8 has a 160 in it and manual dictating it too. She runs dead on 153 99% of the time on smart craft reading

 

[Lou C]

Merc switched to the 160 when they started using throttle body EFI, before that if you look in their manuals and parts listings the raw water cooled stats were just about always 140*.
In fact I was really surprised my brother's nearly new 2020 Merc 4.5 V6 has a 140, yes it does for sure and it runs at a cool 120-140. Mine with the 160 runs between 160 and 175.
For closed cooling I can't see why they'd spec the 140 since that loses one of the advantages of closed cooling in the first place, the warmer operating temp is better for engine life. As long as the raw water pump and the H/E had adequate capacity to cool the engine.

Yet if you look at outboards what do they have? 120-140 stats. They run really cool for raw water cooling.

 

[QBhoy]

Merc switched to the 160 when they started using throttle body EFI, before that if you look in their manuals and parts listings the raw water cooled stats were just about always 140*.
In fact I was really surprised my brother's nearly new 2020 Merc 4.5 V6 has a 140, yes it does for sure and it runs at a cool 120-140. Mine with the 160 runs between 160 and 175.
For closed cooling I can't see why they'd spec the 140 since that loses one of the advantages of closed cooling in the first place, the warmer operating temp is better for engine life. As long as the raw water pump and the H/E had adequate capacity to cool the engine.

Yet if you look at outboards what do they have? 120-140 stats. They run really cool for raw water cooling.

Weird one eh. I know my 2016 merc outboard runs really cool (as it’s meant to) runs about 130 or less.

 

[Lou C]

I think this is why the 'making oil' issue is a thing with some 4 stroke outboards, the water vapor doesn't get burnt off if they are not run hard and it causes the oil level to rise.
What I found when I tried a 140 stat in mine was that I had condensation in the exhaust manifolds (found this by accident, pulled off the manis when I had to change the leaky old steering actuator and had run the engine about an hr before). Did not like that so I went back to the 160. OMC/Volvo always used the "cold manfold" set up where the manis are fed constantly cool water from the impeller, it gets warmer when the engine warms up and the stat opens but not that much, so they run pretty cool. Merc on the other hand used both, a cool manifold and warm manifold set up. The idea was to keep the manis warm enough to prevent condensation (hotter than 120*) so they didn't get cooling water till the engine stat opened up.

 

[Scott06]

Merc switched to the 160 when they started using throttle body EFI, before that if you look in their manuals and parts listings the raw water cooled stats were just about always 140*.
In fact I was really surprised my brother's nearly new 2020 Merc 4.5 V6 has a 140, yes it does for sure and it runs at a cool 120-140. Mine with the 160 runs between 160 and 175.
For closed cooling I can't see why they'd spec the 140 since that loses one of the advantages of closed cooling in the first place, the warmer operating temp is better for engine life. As long as the raw water pump and the H/E had adequate capacity to cool the engine.

Yet if you look at outboards what do they have? 120-140 stats. They run really cool for raw water cooling.

Mine is carbed and has the 160 from factory, wasn’t just efi

 

[QBhoy]

Mine is carbed and has the 160 from factory, wasn’t just efi

89 and 91 boats I had with 4.3’ carbs were both 160. Remember those two in particular

 

[Rick Stephens]

Thinking similar to some others. You may have the wrong gaskets or set up in the riser to manifolds. But I’d also always thought a 140 t stat is for closed cooling engines. 160 is for raw.
I once had to bleed air out the circ pump housing on an engine to get water around it. Afterwards found out it was drawing air in from the cooler that’s fitted on the intake line between outdrive and engine. That was a different set up to yours though.

The reason for lower temperature thermostats on open cooling the lack of pressure. With closed cooling and 14 pound cap the water won't create vapor bubbles until after 220ƒ. With open cooled motors the low pressure allows vapor bubbles to form at 170-175ƒ or even lower when at altitude. Bubbles severely reduce the cooling capability. Heads start getting hot first and then you get cracks in the jacket.