350 mag mpi manifold/elbow temp

[Mhorn0817]

2011 350 mag mpi, raw water cooled.

Just installed brand new manifolds and elbows and hoping someone could give me approximate temperature my manifold and elbows should be at idle and when coming off plane.

At idle, port is 150 and starboard is 130. At 3500rpm in neutral, port is 135 and starboard is 115. Now what really has me concerned is after running around for an hour and checking temps, port was 190 and starboard was 170. Motor stays at 150 and thermostat housing was 120. Manifold and elbows are the same temperature. No codes and no power reduction mode, temps just seem high.

 

[saaristo]

Do you have what's called hot manifolds system on your motor? Is there separate hoses going to manifold and elbow?

 

[Mhorn0817]

Yes there are separate hoses going to the bottom of the manifolds and well as a hose going to each elbow.

 

[alldodge]

I don't see a problem with your temps

 

[Mhorn0817]

Everything I have found says the elbows and manifolds should always be able to be touched. Found a few things says temps should be anywhere between 120-150 at any given time.

 

[Scott06]

Is this a salt or fresh water boat? The one side is getting on the edge of hot might be worth taking off elbows to see what passages look like in terms of scale and corrosion

 

[Mhorn0817]

Brackish water. I can take them back off but I just Installed the manifolds and elbows, brand new oem and then took out for a test run.

 

[harringtondav]

You should be able to touch the elbows. The manifolds are hotter because They're in direct contact with the exhaust gasses, and the exhaust cooling circuit pulls off the most heat there. I touched mine once, and that was enough. If your elbows aren't excessively hot you're exhaust cooling is working.

 

[alldodge]

Motor stays at 150 and thermostat housing was 120.

The temp variations between the elbows does not concern me, only the actual temps, that is if the temps are correct. Don't see how the gauge can show 150 and the housing show 120 where the sender is located (assuming 4 port housing).

Maybe a serial number might help to know what your housing looks like

 

[Scott06]

Everything I have found says the elbows and manifolds should always be able to be touched. Found a few things says temps should be anywhere between 120-150 at any given time.

They will be hot to the touch, you can put your hand on them but you dont want to leave it there long. If you just replaced manis and elbiws you are prob fine. to give yourself some piece of mind have you verified the flow to thermostat housing ? If you have the poppet valves feeding elbows they can sometimes not restrict flow and bypass too much raw water.

120-150 is way colder than what ive seen , of course depends on water temp a bit.

 

[Lou C]

Use an IR temp gun I keep one on the boat for testing.
If it’s the Merc warm manifolds system the manifolds don’t get water circulation till the engine thermostat opens so they should be as warm as the engine block. The elbows get cool water continuously so they should be cooler. The idea behind this was Merc wanted to eliminate condensation in the exhaust manifolds which can happen if you get temps below 120*F.
The only other cause might be that the impeller needs replacing, every 3 seasons is a good interval. That and the off chance that a flapper melted & fell off & blocked the exhaust on one side…

Volvo & OMC always used cool manifolds and used a 160 stat to compensate. I tried a 140 stat on mine once & had condensation in the manifolds so went back to the 160. Even in salt water.

As far as checking the thermostat housing, I can’t say on a Merc unit but on the OMC/Volvo housing used on many engines it will read low in the top & sides due to water flow but if you check the temp of the intake manifold right under the stat housing it will read very close to the dash gauge about 10-15* less than the gauge.
On my OMC with later style exhaust (2 piece vs original bat wings) at idle they are at 95-100 and after coming off plane the hottest they get is about 135*. Same as the old batwings.

 

[Mhorn0817]

.Poppet valves were checked and are good.
. Flappers looked good when replacing elbows and manifolds.
.Used a IR temp gauge to measure temps.
.It is a 4 port housing.
.All temps taken with boat warmed up. High number were after a hour long cruise, mostly at 3800 rpms.
.Impeller is brand new.

 

[alldodge]

Things don't add up

If 150 is correct then 190 isn't

If 150 is not correct, (take reading at sendor not on top of housing) then maybe bravoits or air leak

 

[Mhorn0817]

I took the motor temp reading on the housing. I should've done it at the motor or intake manifold. Regular gauge and smart craft gauge both say 150 motor temp.

 

[alldodge]

Does the motor have a 3 point or 7 point drain system?

 

[Mhorn0817]

3 point.

 

[Mhorn0817]

Serial number is 1A643152

 

[alldodge]

The serial number helps a bunch, you have CAT's
When I mentioned 4 port Stat, I was thinking this


With CAT you have a different 4 port, and should have a 160* thermostat


Also having CAT's the mans should get hotter then others, how hot I don't know because don't have the manual, but @muc might. Same with a car CAT it gets really hot

Look at the hose routing in the link and item 29 is a Y fitting which transfers raw waater straight to the elbows thru Green Tee fitting item 20. The Tee fitting creates a restriction to keep the motor and Mans full. Water flows more freely thru the motor only when the thermostat opens.

Water always flows the path of least resistance.

So unless the Mans should stay cooler I'm back to there is no issue

 

[Lou C]

Yep if you have cats at least in a vehicle they routinely run 400* and even hotter. So we can’t really use non cat exhaust temps as a guide here…

 

[Mhorn0817]

EC motor but I removed the cats and added the 02 sensor bypass kit.