Exhaust riser temperatures

[Hydravion]

Hi all,
Just a question regarding the exhaust riser temperatures.
One side is very hot, with a reading of 82 degrees C, and on the other side its a warm 50 degrees C. with the engine running at 1100rpm

Also the temperature gauge is fluctuating between 76 degrees and 64 degrees.
Engine is a Volvo-penta 4.3 GXIE M.
Has anyone had this problem with their engines.

 

[Scott Danforth]

First, welcome aboard.

it is not uncommon for one side to be warmer than the other. especially on muffs running on a trailer

however your 82C seams a bit excessive.

were these temps taken in the water, or on muffs?
when was the last time the elbows were removed and the manifolds inspected?
when was the last raw water pump service done?

 

[stresspoint]

i had the same problem with my 4.3 mercruiser vortec motor , after some discussion it was determined that it was normal for different temps .

my OCD did not take kindly to me being able to hold my hand on one riser and the other was almost too hot to touch .
i made up a set of restrictors to slip into the hoses , this evened out the temps to within a few degrees ,
it probably made no difference to performance or reliability but it made me sleep better knowing the temps were acceptable.

im not 100 % on the volvo , but the early 4.3 mercruiser had a weird assed valve in the Tstat housing that equalized the water flow.im not sure how that worked or if it did anything at all but i figured that it might be worth a mention since you are having this issue.

 

[Horigan]

In my view, if you can't hold your hand on the riser, it's too hot and there is a flow restriction.

 

[harringtondav]

I'd first go with SD's question in #2 above about the raw water impeller. I've heard this type of impeller should be replaced more often than a Merc Alpha lower housing impeller.
Also judging manifold heat on muffs can be tricky. Too little flow, or too much can cause excess heat. Merc states to open the hose faucet only about half for an Alpha. My VP 4.3 only states to monitor engine temp at the dash gage. ...I forgot to turn the muff hose on last spring when recommissioning. The exhaust temp sensors and alarm told be about it right away.
Try replacing the impeller and make the same touch test when you get the boat back into the water.

 

[cptbill]

Some questions, Have you ever had in impeller go bad? Changed a thermostat? are you in salt water? There are some small passage ways in the thermostat housing that can get plugged or partly. As was said it's common for the risers to be different temps. but that spread also seems a little much to me also

 

[Lou C]

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I'm thinking you have this exhaust on your engine, I have the same on my old OMC, on mine here are the temps I usually get:
idle, on the water hose: top of elbow, 75-80* F (24-27*C)
idle after running at hull speed in the water, 110-115*F (43-46*C)
bringing it back to idle after running on plane, 135-140*F (57-60*C)
at idle the starboard side is usually slightly higher than port.
your temp of 82* C (180*F) seems quite a bit too high
I'd be checking the impeller, and for a blockage in the thermostat housing nipple that feeds that side and the manifold/elbow water passages for that side.
How is your engine temp? Should be 160*F-175*F or so (71*C-80*C)
The only time in the past I saw elbow temps as high as 160 was when my boat sucked up sand and it needed a new impeller.

 

[Dillusion808]

Since one side is so much hotter I'm going to go with when was the last time you check the manifolds and elbows for corrosion?

 

[BRICH1260]

I`d suggest you start by removing the thermostat housing and thoroughly cleaning out the internal passages. There are a few that can be hard to find if you do not know where to look.

 

[Lou C]

Here are a couple of pix of the OMC/Volvo thermostat housing. Yes OMC designed it and Volvo just used it when they bought into OMC's sterndrive division....
especially in salt water the passages can get necked down just like the passages for the manifolds and elbows, it is a good idea to rod them out periodically. The passage that is easy to miss is the bypass because it is above the thermostat housing you can't see it with the 'stat in place.