Engine temp running too low

[nhuyck]

I have a 2002 Four Winns 298 Vista with twin 5.0 liter Gxi's with duo prop out drives and a raw water cooling system. The engine temp on STB engine runs between 160 and 170 on gauge. (perfect) My port engine however runs between 110 and 130. After reading previous posts, I yanked off the Thermostat housing and sniffed around for impeller chunks. I unscrewed the 90* elbow on the bypass and sure enough found a chunk of impeller. Fished out the chunk and did a thorough search around the housing for more peices and found none/ Placed a new o-ring and thermostat in it and I am still running on the cool side, still topping out at 130. Any ideas on what to start with next? I verified gauge with a heat gun and the gauge/sending unit are not the problem. Thanks.

 

[Robbabob]

I'm not familiar with your engines, so take my input with a large grain of salt! If there is a t-stat, sounds like it needs to be replaced. It is not allowing your engine to get up to temp, thus opening too soon and the engine stays cooler.

If I am wrong, let it be a lesson to everyone reading my answers LOL

Good luck!

 

[jerryjerry05]

Look on the thermo, it might have a number stamped in there??
Real desperate, swap them around?
Or like Robabob suggested get a new one.

 

[bruceb58]

Get an IR gun and verify that what your gauge says is correct. Check both engines and compare to each other.

 

[BRICH1260]

I had the same issue with my 5.0 in my last boat. Come to find out the bypass port was plugged with impeller rubber. Even when it was cleaned out thuroughly and a new thermostat was installed, it never ran at 160. It did warm up some, just not to what the book says it should be.

 

[further]

Just had the same issue and it wasn't impeller rubber. I put in a brandy new impeller, pump, tstat housing and tstat and it wasn't warming up so I removed the tstat housing (thinking maybe the new tstat was lodged open or something) but it was fine. Ended up that the bypass port was clogged up with sand/debris of some sort (possibly a byproduct of the casting/manufacturing process). So either way i'd go through your tstat housing with a stiff wire and clean out all the passages. Make sure you get at the bypass port (look at the diagram in the shop manual) because its not readily accessible and you have to play with it a bit to get the wire in there.
Good luck

 

[nhuyck]

Thank you for all the replies, it ended up being a piece of debris the size of a pencil eraser. I rigged up a flexible wire brush and put it on a drill and ran it through the bypass (there are two areas the bypass passes through). Both engines run 160-170 now....perfect.

 

[further]

Glad to hear. That bypass seems to be the culprit every time.