Mercruiser 4.3 LX running cool?

[cwoodffr]

87 model year. Last season the temp gauge stopped working (stayed left peg -120). I figured it was the temp sender because when you ground the wire at the engine it pegs the gauge. Replaced the sender....and still no temp reading. My conclusion is that somehow the thermostat has failed in an open position. Seemed unlikely to me but I can't think of any other reason...other than the gauge is faulty anyway. I picked up a replacement stat and gasket....but the guy must have heard me wrong because it is way smaller than what is in there....so I didn't pull the old one out yet. Seems like the plastic sleeve is going to be difficult to get out. just though I would solicit opinions

 

[Don S]

Re: Mercruiser 4.3 LX running cool?

Get one of those IR temp guns and check the actual engine temp at the sending unit. If you actually are low, replace the thermstat.
The 4.3LX used several setups for the thermostat, hard to say what unit you actually have. SN of the engine would help. is it raw water cooled, or do you have a heat exchanger?

 

[cwoodffr]

Re: Mercruiser 4.3 LX running cool?

Its raw water. I was aiming for a 160 but I think the parts guy heard 3 vs 4.3 and the stat he gave me looks like it would fit in a mcdonalds straw!

 

[greiffster]

Re: Mercruiser 4.3 LX running cool?

I replaced the thermostat in a '96 5.0L and the white plastic sleeve was all but bonded to the housing. No way to get it out without destroying it. It's about a 7-10 buck item that I ordered with the t-stat.

 

[sdoomaha]

Re: Mercruiser 4.3 LX running cool?

My t-stat was stuck closed on my 4.3 and the gauge still showed it was reading cool. The temp sending unit is on the cool side of the t-stat on my t-stat housing. T-stat was never letting coolant out from the block to reach the temp sending unit. T-stat and sleeve came out easy...hit it with wd-40 ane let it sit for a few minutes. Used a hammer on the backside of the t-stat and it and the sleeve came out together rather easy.

Good Luck.

 

[cwoodffr]

Re: Mercruiser 4.3 LX running cool?

Well, I think the stat was opening too soon or something. I pulled the old one and it was closed...so much for the stuck open theory. I put it in hot water and it seemed to operate normally but I didn't have the patience to watch the temp carefully and see what it was actually doing. I put the new one in and with a short idle warm up, slow trip out of the marina and into open water and it was showing a temp a bit above 120 (first time I had seen the needle move in two seasons). It then came up to about 165 and stayed there. Engine seemed like it was producing way more power! Would it make that much difference to get some heat? I guess with a carb its important. Anyway, running great and way stronger it would seem and I now know what the temp is!