rtf01

I have a Mercruiser 5.0 MPI and I am wondering what normal Manifold Air Temperature (MAT) readings. The engine was running at 1400 RPM's for about 9 mins and the Manifold Air Temperature kept rising from 62% F when engine started to 82.40 % when engine was turned off. The coolant temperature rose to 156% F but then maintained that temperature. Is it normal for the Manifold Air Temperature to keep rising and not level off?

Thanks in advance for your reply.

Cap'm Kurt

Well, i have never watched mine that close, but I would guess it would keep rising longer than that 10 minutes. Everything is cool/cold when you start a boat, from all the motor external pieces/brackets/housings, etc, to the engine cover, batteries and wiring, everything in there contributes a little. Takes longer than that to really heat everything up really good in the motor compartment. So it doesn't surprise me that it kept coming up. Read it for 30 minutes it'll be higher. Stop and sit, and at start up it will be even higher. But at some point if your cruising for awhile it will level out. Unless the afternoon ambient temps rise a lot, then it'll go up more.

Just a little common sense on why a compartment with a "heater" in it would keep going up for quite a while(more than 10 minutes), even with some fresh air coming in.