Starboard riser hotter than port on 4.3L

[Hay Boater]

Hello, so after doing a tune up it the starboard riser is noticeably hotter than the port to the touch when using checking with muffs. Had it out once this year and risers were fine. Installed new: impeller kit with housing, shift bushing, thermostat, plugs, wires, dist. cap, and coils. Everything is working fine except the one riser gets warm at mid-throttle. This is a raw water system that's only lived in freshwater lakes of the mid-west.

Have not had it back in the lake so today I did a tank test and noticed reduced water flow out the starboard transom exhaust at times. Temp gauge came up to 160° F and stayed right there. Took the hose off the t-stat housing to the riser and can easily blow air through it. Running different RPM's I noticed different flows. @ 950 RPM's they were equal in flow and temp, @ 2,400 RPM equal in flow and temp, @ 1,800 RPM reduced flow starboard side and hotter riser.

Do I have a problem or is this normal? Thanks in advance for the advice!

 

[Scott Danforth]

so your looking at the idle relief ports..... flow will never be symmetrical

same as coolant flow to the exhaust manifolds. the one that is higher (because someone is standing in the boat causing it to list) is the one that will be warmer

 

[Hay Boater]

That makes sense. Is there a temp range that you would expect the risers to be within one another under normal conditions? 30 deg? 50 deg?

 

[achris]

That makes sense. Is there a temp range that you would expect the risers to be within one another under normal conditions? 30 deg? 50 deg?

It all depends on how much variation in flow. These no set variation....

 

[Hay Boater]

Thanks for the replies!

 

[Scott06]

That makes sense. Is there a temp range that you would expect the risers to be within one another under normal conditions? 30 deg? 50 deg?

No set rule of thumb but what you should do now since it is running at proper temp is either with a calibrated palm or better yet an IR temp gun see how hot they are. That way you know what your engine when running cool is, down the road if you have issues you have a baseline of what good looks like.