omc 5.8 riser temp

[jmarine225]

thanks to this site I believe I may have resolved my overheating issues. I bought an IR temp gun and ran it to check the temp of the risers since my last overheat burned up an exhaust bellows. My temp gauge was around 160 and the temp on the risers I continuously kept shooting was in the area of 170-180 tops. Is the 170-180 riser temp normal or is it running hot still? At the end of the season when I take the boat out of the water I plan on checking the risers for any blockages.

 

[jmarine225]

Re: omc 5.8 riser temp

is there anyone out there who can give me insight on this?

 

[jmarine225]

Re: omc 5.8 riser temp

are these temps normal or is it running hot still? The t-stat on the gauge is fluctuates while running from 160 up to about 175-180 tops then drops back down. I have a 160 t-stat in it now. is that normal also?

 

[futz]

Re: omc 5.8 riser temp

year?

Impeller changed last? yea sounds like a riser manifold, flapper issue"maybe"

Power steering on the boat? Raw water cooled?

 

[frank246]

Re: omc 5.8 riser temp

No.
Take out the 160F, it`s a car thermostat, most marine uses 142F

 

[futz]

Re: omc 5.8 riser temp

most omc's use a 160 t-stat. merc uses the 143. as long as the temp. never gets to 190 your good to go till the winter and do what has to be done.

 

[jmarine225]

Re: omc 5.8 riser temp

its a 93, a new upper drive with impeller was placed on it this season. It does have power steering and when it consistently ran hot the mechanic back flushed it and found parts of an old impeller stuck in the power steering cooler. Recently I have been running it, at most for about 2 hours and the gauge will go up to maybe 180 and then drops back down to about 150-160. Not sure if that is normal or not but seems so since I have a 160 t-stat which is also new. A friend of mine who has the same exact boat says his t-stat which is a 160 gets up in the area here and consistently stays at the same temp.

 

[jmarine225]

Re: omc 5.8 riser temp

okay I believe I may have it resolved. I run the engine for a period of time and the gauge maybe goes up to 175-180 tops then drops back down. (i have a 160 t-stat installed). I have an IR gun to check the temps so what temps should I be seeing off my risers? My risers were replaced at some point in the past as they are aftermarket but the manifolds are the originals. I am concerned I may still overheat at the risers and blow and exhaust bellows even though my gauge is showing a good temp. I also plan on inspecting the risers but can this be done while on the water? I would believe so because if water came in then water would be getting into the engine. Can someone please help me??

 

[a70eliminator]

Re: omc 5.8 riser temp

You can remove the risers, they are well above the waterline. My 1990 351W runs about 160 on the temp guage, all I can say about the actual riser temp. is that I can lay the palm of my hand anywhere on them at any time, they're not even close to 170-180 that seems way too hot.

 

[jmarine225]

Re: omc 5.8 riser temp

Thanks for your help. My main concern is, if my gauge reads 160 then should I be concerned about the temp of the risers? I just don't want to be out on the open water and blow an exhaust hose again. Also the gauge reading 160 measures exactly what temperature? If it is 160 is the engine not overheating at all but the risers may be? Or, could the exhaust manifolds due to age still be hot even though the gauge/t-stat is reading 160? I plan on removing the risers in the next day or so and examining them but these should be my final questions on this matter.

 

[a70eliminator]

Re: omc 5.8 riser temp

The engine temperature sensor is located near the thermostat housing, it's very probable the manifolds and risers are overheating from lack of waterfllow even though engine temp is normal, try pulling the feed tubes off the front of the manifolds and look for rust restriction right there at the nipple, then there is also a plugged nipple at the rear of the manifolds you can pull that plug and try flushing them out, I'm guessing they are full of sediment. The manifolds on my Ford v8 actually run cooler then the motor does.

 

[jmarine225]

Re: omc 5.8 riser temp

okay, I'm gonna check my risers tomorrow and I have no gaskets to install when I remove the risers. I checked the online manuals and I can't this anywhere. Anyone know the required torque on the riser bolts? I have a torque wrench and want to replace the bolts properly.