8.1l Port running hotter

[Nmor830]

just did all new manifolds on my 2008 sundancer 8.1H. While at it saw the raw water pump on the port side was leaking so after researching and reading some threads here decided to replace with the Hardin Gen7 stainless pump. Visually comparing the water flow from both engines it seems there’s just a little less flow from the new pump. Also we checked temps. on both engines with a heat sensor and found the port is 10-15 degrees hotter then strb. Also what’s interesting is the port manifold on the port engine is hotter then the strb. manifold.(port engine)? Ran both engines at the dock for quite awhile and they do stabilize at between 150-165dgrs. Going out for a run this weekend to see how the temps hold. What concerns me is the big difference in temps. between manifolds on the same engine. Anyone have any idea what could be the cause?
Thanks,
Nick

 

[sbw1]

Which engine has the heat exchanger for your hot water heater? That side will run a bit cooler than the other side.

 

[Little Ducky]

View attachment 72712 Which engine has the heat exchanger for your hot water heater? That side will run a bit cooler than the other side.

I would have never thought of that..... good point.

 

[M Prod]

Nmor- what are your water pressure readings and are they accurate? Check that and then swap the sensors to make sure you get the same reading.

I would have never thought of the engine-hot water heater thing either. Without looking I’d assume it’s the port since it’s right next to the hot water heater. That said, my starboard engine also runs cooler than my port engine. Port sticks at 165, and starboard at 150 at idle. These temps are much closer at cruise (165 port and 159 starboard typically). Water pressure is actually lower on starboard, but only by 2 psi or so at 3500 rpm cruise. I did both of my water pumps and impellers last fall and have 80 hours on them currently. I’ll probably go ahead and replace both heat exchangers within the next year or two as these are the original units. If water pressure and flow is fairly consistent between engines and temps are accurate, it’s not really cause for too much concern IMO. It could be a heat exchanger thing, but again ..likely fine for now.

 

[sbw1]

Gauges are not always very accurate and that is another possibility. I've had variations with every boat I've owned. The key thing is to listen and observe how things run. If all is good with that, remember what the gauges say and assume that is the normal for your boat. When those readings change, something is going on that you should wonder about.

 

[M Prod]

View attachment 72727 Gauges are not always very accurate and that is another possibility. I've had variations with every boat I've owned. The key thing is to listen and observe how things run. If all is good with that, remember what the gauges say and assume that is the normal for your boat. When those readings change, something is going on that you should wonder about.

Indeed. My temp readings as stated above have been verified at the engines and water pressure readings verified through swapping sensors (same readings).

 

[Nmor830]

Thanks for all the replies. Would have never thought of the hot water heater either. Yes it is the port side and the pressure gauges read even. Engines seem to run fine at dock but tomorrow will take her out for a shake down run. I’ll report back any unusual findings. Hopefully none. The gauge thing differences might be the issue as well.
Thanks again,
Nick

 

[Jeff Delbuono]

Hhmmm. I have the same issue with my 5.0 efi. Last year both motors ran at 170 all the time. This winter i changed manifolds, spacers, risers as well as installed a new hot water heater and ran the bypass to the starboard motor. Now this year port is still at 170 and starboard is at 120 at idle and only at plane starts to rise to 170. As soon as i pull back it starts to drop to 120 again. Was thinking a piece of something got stuck in thermostate keeping it open. Both new last year. Could it just be normal due to water heater?

 

[Ididntdoit]

Hhmmm. I have the same issue with my 5.0 efi. Last year both motors ran at 170 all the time. This winter i changed manifolds, spacers, risers as well as installed a new hot water heater and ran the bypass to the starboard motor. Now this year port is still at 170 and starboard is at 120 at idle and only at plane starts to rise to 170. As soon as i pull back it starts to drop to 120 again. Was thinking a piece of something got stuck in thermostate keeping it open. Both new last year. Could it just be normal due to water heater?

easy enough to check - just unhook the wh and connect the two ports on the motor

 

[Jeff Delbuono]

Nice. Didnt think of that. Thanks

 

[sbw1]

50 degrees difference seems like a lot for a water heater, especially after your heater is full of hot water. I would look for another cause with out necessarily ruling out the water heater.

 

[sbw1]

If you look closely, the port engine is running about 8 degrees cooler than the starboard engine. Port side warms the water heater. The difference gets smaller after running for six or seven hours, but there always a difference.