Manifold/Riser Temp Inbalence and Bucket Test.

msd58

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I noticed that my starboard manifold and riser temp definitely feels hotter than my port manifold and riser temp. I can place my hands on manifold and risers on starboard side but not as long as I can on the cooler port side. Someone recommended I try the bucket test that involves disconnecting the hoses that go into manifold, placing buckets under them and start engine to see what bucket fills up first. Surprisingly the starboard side (hotter side) filled up twice and fast as colder side. I would have thought the opposite would have occurred. Motor is a single 7.4 MPI, 425 hours, risers and elbows replaced 4 years ago, RWC and in fresh water. All water pumps new. Engine temp runs normally between 165-175* I did not use heat gun to see what manifold and riser temps are what the differences are. Hope to do that soon. Can anyone comment on this?
 
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Scott Danforth

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one side is always a bit warmer than the other. if you can keep your hand on the manifold, then you are about 180F.
 

msd58

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one side is always a bit warmer than the other. if you can keep your hand on the manifold, then you are about 180F.

Left me clarify. The temp of 165-175* was from my dash gauge. Secondly the starboard risers feel hot compared to cooler port side.
 

bruceb58

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If this is a Bravo drive, you should not be running this in a bucket. If it's an Alpha, you need to make sure the water level is over the level of the impeller.
 

msd58

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If this is a Bravo drive, you should not be running this in a bucket. If it's an Alpha, you need to make sure the water level is over the level of the impeller.

Boat is in the water. Hoses that were disconnected from manifolds connect to t stat housing. I believe you did not understand the post.
 

bruceb58

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You are correct, Now that I re-read it I understand what you were saying and testing.

Would be interesting to test the actual temp differences with an IR gun. My Volvo has close to 20 degree differences at idle.

What you should really do is test the manifold temps after a run while on plane.

Are you flappers in your exhaust still intact? An over heated flapper that drops in your exhaust tube can cause what you are seeing.
 
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msd58

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To my knowledge the flappers are ok. I will check temp differences between the two side with IR gun next time I am down to boat. If anyone else wants to weigh in on this topic, feel free.
 

msd58

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The difference between the two side after warm up at idle was on average 10-15* Max temp on warm side after coming of plane was about 40* Manifold on warm side reach a max temp of 140*
 

Bondo

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Ayuh,.... Sounds like she's runnin', 'n coolin' just Fine to me,....
 

msd58

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The difference between the two side after warm up at idle was on average 10-15* Max temp on warm side after coming of plane was about 40* Manifold on warm side reach a max temp of 140*

Let me clarify. After coming off plane temp difference was 40* between the two sides with max temp on warmer side at 140*
 

Lou C

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If your max temp is about 140 that's fine. I've been checking mine for years and the risers are usually at 135/125 after coming off plane.
At idle they are at about 100.
 

msd58

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I wanted to add one more observation that I forgot. I took readings using IR temp gun on the t-stat housing. The starboard side of housing where the hose that goes to manifold attaches was definitely warmer than the port side.
 

Lou C

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You might want to remove the housing to make sure the passageways to each manifold are open to the same extent.
 
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