Mercruiser temp question

[zootschief]

I just put my boat in and it has a 120hp Mercruiser(21ft boat) I had an issue with the temp going up to 180.I removed the thermostat and it is at 120 but when i go to WOT the temp goes up as soon as I accelerate, My question is Impeller? exhaust elbow? or Thermostat?

 

[Samsara]

180F?, it's just nice ! My 2005 twin 350 mag mpi can go up to 190F-195F when WOT, and yet my risers are only slightly warm to touch.
Not sure about your engine's year, I heard that newer merc engines can support easily up to 200F.

 

[makomark]

Put the t-stat back in...your engine will appreciate it.

Given the limited info you shared, I'd guess impeller or exhaust elbow...I'm sure the issue is raw water flow but the root cause is for you to determine.

 

[guyjg]

120hp Mercruiser(21ft boat)

That's alot of boat for a little engine. As stated, install a new Merc. impeller first. If the old one is not intact upon removal you need to backflush from the thermostat to get the pieces out.